Merge pull request #8620 from taosdata/feature/sync-implementation

Feature/sync implementation

include/libs/sync/sync.h

@@ -26,7 +26,7 @@ extern "C" {
 typedef int32_t  SyncNodeId;
 typedef int32_t  SyncGroupId;
 typedef int64_t  SyncIndex;
-typedef uint64_t SSyncTerm;
+typedef uint64_t SyncTerm;
 
 typedef enum {
   TAOS_SYNC_ROLE_FOLLOWER = 0,
@@ -61,13 +61,13 @@ typedef struct {
 typedef struct SSyncFSM {
   void* pData;
 
-  // apply committed log, bufs will be free by raft module
+  // apply committed log, bufs will be free by sync module
   int32_t (*applyLog)(struct SSyncFSM* fsm, SyncIndex index, const SSyncBuffer* buf, void* pData);
 
   // cluster commit callback
   int32_t (*onClusterChanged)(struct SSyncFSM* fsm, const SSyncCluster* cluster, void* pData);
 
-  // fsm return snapshot in ppBuf, bufs will be free by raft module
+  // fsm return snapshot in ppBuf, bufs will be free by sync module
   // TODO: getSnapshot SHOULD be async?
   int32_t (*getSnapshot)(struct SSyncFSM* fsm, SSyncBuffer** ppBuf, int32_t* objId, bool* isLast);
 
@@ -89,19 +89,30 @@ typedef struct SSyncLogStore {
   // write log with given index
   int32_t (*logWrite)(struct SSyncLogStore* logStore, SyncIndex index, SSyncBuffer* pBuf);
 
+  /** 
+   * read log from given index(included) with limit, return the actual num in nBuf,
+   * pBuf will be free in sync module
+   **/
+  int32_t (*logRead)(struct SSyncLogStore* logStore, SyncIndex index, int limit,
+                      SSyncBuffer* pBuf, int* nBuf);
+
   // mark log with given index has been commtted
   int32_t (*logCommit)(struct SSyncLogStore* logStore, SyncIndex index);
 
-  // prune log before given index
+  // prune log before given index(not included)
   int32_t (*logPrune)(struct SSyncLogStore* logStore, SyncIndex index);
 
-  // rollback log after given index
+  // rollback log after given index(included)
   int32_t (*logRollback)(struct SSyncLogStore* logStore, SyncIndex index);
+
+  // return last index of log
+  SyncIndex (*logLastIndex)(struct SSyncLogStore* logStore);
 } SSyncLogStore;
 
 typedef struct SSyncServerState {
   SyncNodeId voteFor;
-  SSyncTerm  term;
+  SyncTerm  term;
+  SyncIndex  commitIndex;
 } SSyncServerState;
 
 typedef struct SSyncClusterConfig {
@@ -122,9 +133,9 @@ typedef struct SStateManager {
 
   int32_t (*readServerState)(struct SStateManager* stateMng, SSyncServerState* state);
 
-  // void (*saveCluster)(struct SStateManager* stateMng, const SSyncClusterConfig* cluster);
+  void (*saveCluster)(struct SStateManager* stateMng, const SSyncClusterConfig* cluster);
 
-  // const SSyncClusterConfig* (*readCluster)(struct SStateManager* stateMng);
+  const SSyncClusterConfig* (*readCluster)(struct SStateManager* stateMng);
 } SStateManager;
 
 typedef struct {
@@ -146,13 +157,13 @@ SSyncNode* syncStart(const SSyncInfo*);
 void       syncReconfig(const SSyncNode*, const SSyncCluster*);
 void       syncStop(const SSyncNode*);
 
-int32_t syncPropose(SSyncNode* syncNode, SSyncBuffer buffer, void* pData, bool isWeak);
+int32_t syncPropose(SSyncNode* syncNode, const SSyncBuffer* pBuf, void* pData, bool isWeak);
 
 // int32_t syncAddNode(SSyncNode syncNode, const SNodeInfo *pNode);
 
 // int32_t syncRemoveNode(SSyncNode syncNode, const SNodeInfo *pNode);
 
-extern int32_t syncDebugFlag;
+extern int32_t sDebugFlag;
 
 #ifdef __cplusplus
 }

source/libs/sync/CMakeLists.txt

@@ -4,6 +4,7 @@ add_library(sync ${SYNC_SRC})
 target_link_libraries(
     sync
     PUBLIC common
+    PUBLIC transport
     PUBLIC util
     PUBLIC wal
 )

source/libs/sync/inc/raft.h

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _TD_LIBS_SYNC_RAFT_H
+#define _TD_LIBS_SYNC_RAFT_H
+
+#include "sync.h"
+#include "sync_type.h"
+#include "raft_message.h"
+#include "sync_raft_impl.h"
+#include "sync_raft_quorum.h"
+
+typedef struct RaftLeaderState {
+
+} RaftLeaderState;
+
+typedef struct RaftCandidateState {
+  /* true if in pre-vote phase */
+  bool inPreVote;
+} RaftCandidateState;
+
+typedef struct SSyncRaftIOMethods {
+  // send SSyncMessage to node
+  int (*send)(const SSyncMessage* pMsg, const SNodeInfo* pNode);
+} SSyncRaftIOMethods;
+
+typedef int   (*SyncRaftStepFp)(SSyncRaft* pRaft, const SSyncMessage* pMsg);
+typedef void  (*SyncRaftTickFp)(SSyncRaft* pRaft);
+
+struct SSyncRaft {
+  // owner sync node
+  SSyncNode* pNode;
+
+  SSyncCluster cluster; 
+
+  int selfIndex;
+  SyncNodeId selfId;
+  SyncGroupId selfGroupId;
+
+  SSyncRaftIOMethods io;
+
+  SSyncFSM      fsm;
+  SSyncLogStore logStore;
+  SStateManager stateManager;
+
+  union {
+    RaftLeaderState leaderState;
+    RaftCandidateState candidateState;
+  };
+
+  SyncTerm term;
+  SyncNodeId voteFor;
+
+  SSyncRaftLog *log;
+
+  int maxMsgSize;
+  SSyncRaftProgressTracker *tracker;
+
+  ESyncRole state;
+
+  // isLearner is true if the local raft node is a learner.
+  bool isLearner;
+
+  /**
+   * the leader id
+  **/
+  SyncNodeId leaderId;
+
+	/**
+   * leadTransferee is id of the leader transfer target when its value is not zero.
+	 * Follow the procedure defined in raft thesis 3.10.
+   **/
+  SyncNodeId leadTransferee;
+
+	/**
+   * Only one conf change may be pending (in the log, but not yet
+	 * applied) at a time. This is enforced via pendingConfIndex, which
+	 * is set to a value >= the log index of the latest pending
+	 * configuration change (if any). Config changes are only allowed to
+	 * be proposed if the leader's applied index is greater than this
+	 * value.
+   **/
+  SyncIndex pendingConfigIndex;
+
+	/** 
+   * an estimate of the size of the uncommitted tail of the Raft log. Used to
+	 * prevent unbounded log growth. Only maintained by the leader. Reset on
+	 * term changes.
+   **/
+  uint32_t uncommittedSize;
+ 
+	/** 
+   * number of ticks since it reached last electionTimeout when it is leader
+	 * or candidate.
+	 * number of ticks since it reached last electionTimeout or received a
+	 * valid message from current leader when it is a follower.
+  **/
+  uint16_t electionElapsed;
+
+	/**
+   *  number of ticks since it reached last heartbeatTimeout.
+	 * only leader keeps heartbeatElapsed.
+   **/
+  uint16_t heartbeatElapsed;
+
+  bool preVote;
+  bool checkQuorum;
+
+  int heartbeatTimeout;
+  int electionTimeout;
+
+	/**
+   * randomizedElectionTimeout is a random number between
+	 * [electiontimeout, 2 * electiontimeout - 1]. It gets reset
+	 * when raft changes its state to follower or candidate.
+   **/
+	int randomizedElectionTimeout;
+	bool disableProposalForwarding;
+
+  // current tick count since start up
+  uint32_t currentTick;
+
+  SyncRaftStepFp stepFp;
+
+  SyncRaftTickFp tickFp;
+};
+
+int32_t syncRaftStart(SSyncRaft* pRaft, const SSyncInfo* pInfo);
+int32_t syncRaftStep(SSyncRaft* pRaft, const SSyncMessage* pMsg);
+int32_t syncRaftTick(SSyncRaft* pRaft);
+
+#endif /* _TD_LIBS_SYNC_RAFT_H */
\ No newline at end of file

source/libs/sync/inc/raft_configuration.h

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _TD_LIBS_SYNC_RAFT_CONFIGURATION_H
+#define _TD_LIBS_SYNC_RAFT_CONFIGURATION_H
+
+#include "sync.h"
+#include "sync_type.h"
+
+// return -1 if cannot find this id
+int syncRaftConfigurationIndexOfNode(SSyncRaft *pRaft, SyncNodeId id);
+
+int syncRaftConfigurationVoterCount(SSyncRaft *pRaft);
+
+#endif  /* _TD_LIBS_SYNC_RAFT_CONFIGURATION_H */
\ No newline at end of file

source/libs/sync/inc/raft_log.h

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _TD_LIBS_SYNC_RAFT_LOG_H
+#define _TD_LIBS_SYNC_RAFT_LOG_H
+
+#include "sync.h"
+#include "sync_type.h"
+
+typedef enum SyncEntryType {
+  SYNC_ENTRY_TYPE_LOG = 1,
+}SyncEntryType;
+
+struct SSyncRaftEntry {
+  SyncTerm term;
+
+  SyncIndex index;
+
+  SyncEntryType type;
+
+  SSyncBuffer buffer;
+};
+
+struct SSyncRaftLog {
+  SyncIndex uncommittedConfigIndex;
+
+  SyncIndex commitIndex;
+
+  SyncIndex appliedIndex;
+
+
+};
+
+SSyncRaftLog* syncRaftLogOpen();
+
+SyncIndex syncRaftLogLastIndex(SSyncRaftLog* pLog);
+
+SyncIndex syncRaftLogSnapshotIndex(SSyncRaftLog* pLog);
+
+SyncTerm syncRaftLogLastTerm(SSyncRaftLog* pLog);
+
+bool syncRaftLogIsUptodate(SSyncRaftLog* pLog, SyncIndex index, SyncTerm term);
+
+int syncRaftLogNumOfPendingConf(SSyncRaftLog* pLog);
+
+bool syncRaftHasUnappliedLog(SSyncRaftLog* pLog);
+
+SyncTerm syncRaftLogTermOf(SSyncRaftLog* pLog, SyncIndex index);
+
+int syncRaftLogAppend(SSyncRaftLog* pLog, SSyncRaftEntry *pEntries, int n);
+
+int syncRaftLogAcquire(SSyncRaftLog* pLog, SyncIndex index, int maxMsgSize,
+                      SSyncRaftEntry **ppEntries, int *n);
+
+void syncRaftLogRelease(SSyncRaftLog* pLog, SyncIndex index,
+                      SSyncRaftEntry *pEntries, int n);
+
+bool syncRaftLogMatchTerm();
+
+static FORCE_INLINE bool syncRaftLogIsCommitted(SSyncRaftLog* pLog, SyncIndex index) {
+  return pLog->commitIndex > index;
+}
+
+#endif  /* _TD_LIBS_SYNC_RAFT_LOG_H */

source/libs/sync/inc/raft_message.h

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _TD_LIBS_SYNC_RAFT_MESSAGE_H
+#define _TD_LIBS_SYNC_RAFT_MESSAGE_H
+
+#include "sync.h"
+#include "sync_type.h"
+
+/** 
+ * below define message type which handled by Raft.
+ * 
+ * internal message, which communicate between threads, start with RAFT_MSG_INTERNAL_*.
+ * internal message use pointer only and stack memory, need not to be decode/encode and free.
+ * 
+ * outter message start with RAFT_MSG_*, which communicate between cluster peers,
+ * need to implement its decode/encode functions.
+ **/
+typedef enum RaftMessageType {
+  // client propose a cmd
+  RAFT_MSG_INTERNAL_PROP = 1,
+
+  // node election timeout
+  RAFT_MSG_INTERNAL_ELECTION = 2,
+
+  RAFT_MSG_VOTE = 3,
+  RAFT_MSG_VOTE_RESP = 4,
+
+  RAFT_MSG_APPEND = 5,
+  RAFT_MSG_APPEND_RESP = 6,
+} RaftMessageType;
+
+typedef struct RaftMsgInternal_Prop {
+  const SSyncBuffer *pBuf;
+  bool isWeak;
+  void* pData;
+} RaftMsgInternal_Prop;
+
+typedef struct RaftMsgInternal_Election {
+
+} RaftMsgInternal_Election;
+
+typedef struct RaftMsg_Vote {
+  SyncRaftElectionType cType;
+  SyncIndex lastIndex;
+  SyncTerm lastTerm;
+} RaftMsg_Vote;
+
+typedef struct RaftMsg_VoteResp {
+  bool rejected;
+  SyncRaftElectionType cType;
+} RaftMsg_VoteResp;
+
+typedef struct RaftMsg_Append_Entries {
+  // index of log entry preceeding new ones
+  SyncIndex index;
+
+  // term of entry at prevIndex
+  SyncTerm term;
+
+  // leader's commit index.
+  SyncIndex commitIndex;
+
+  // size of the log entries array
+  int nEntries;
+
+  // log entries array
+  SSyncRaftEntry* entries;
+} RaftMsg_Append_Entries;
+
+typedef struct RaftMsg_Append_Resp {
+  SyncIndex index;
+} RaftMsg_Append_Resp;
+
+typedef struct SSyncMessage {
+  RaftMessageType msgType;
+  SyncTerm term;
+  SyncGroupId groupId;
+  SyncNodeId from;
+
+  union {
+    RaftMsgInternal_Prop propose;
+
+    RaftMsgInternal_Election election;
+
+    RaftMsg_Vote vote;
+    RaftMsg_VoteResp voteResp;
+
+    RaftMsg_Append_Entries appendEntries;
+    RaftMsg_Append_Resp appendResp;
+  };
+} SSyncMessage;
+
+static FORCE_INLINE SSyncMessage* syncInitPropMsg(SSyncMessage* pMsg, const SSyncBuffer* pBuf, void* pData, bool isWeak) {
+  *pMsg = (SSyncMessage) {
+    .msgType = RAFT_MSG_INTERNAL_PROP,
+    .term = 0,
+    .propose = (RaftMsgInternal_Prop) {
+      .isWeak = isWeak,
+      .pBuf = pBuf,
+      .pData = pData,
+    },
+  };
+
+  return pMsg;
+}
+
+static FORCE_INLINE SSyncMessage* syncInitElectionMsg(SSyncMessage* pMsg, SyncNodeId from) {
+  *pMsg = (SSyncMessage) {
+    .msgType = RAFT_MSG_INTERNAL_ELECTION,
+    .term = 0,
+    .from = from,
+    .election = (RaftMsgInternal_Election) {
+
+    },
+  };
+
+  return pMsg;
+}
+
+static FORCE_INLINE SSyncMessage* syncNewVoteMsg(SyncGroupId groupId, SyncNodeId from,
+                                                SyncTerm term, SyncRaftElectionType cType, 
+                                                SyncIndex lastIndex, SyncTerm lastTerm) {
+  SSyncMessage* pMsg = (SSyncMessage*)malloc(sizeof(SSyncMessage));
+  if (pMsg == NULL) {
+    return NULL;
+  }
+  *pMsg = (SSyncMessage) {
+    .groupId = groupId,
+    .from = from,
+    .term = term,
+    .msgType = RAFT_MSG_VOTE,
+    .vote = (RaftMsg_Vote) {
+      .cType = cType,
+      .lastIndex = lastIndex,
+      .lastTerm = lastTerm,
+    },
+  };
+
+  return pMsg;
+}
+
+static FORCE_INLINE SSyncMessage* syncNewVoteRespMsg(SyncGroupId groupId, SyncNodeId from,
+                                                  SyncRaftElectionType cType, bool rejected) {
+  SSyncMessage* pMsg = (SSyncMessage*)malloc(sizeof(SSyncMessage));
+  if (pMsg == NULL) {
+    return NULL;
+  }
+  *pMsg = (SSyncMessage) {
+    .groupId = groupId,
+    .from = from,
+    .msgType = RAFT_MSG_VOTE_RESP,
+    .voteResp = (RaftMsg_VoteResp) {
+      .cType = cType,
+      .rejected = rejected,
+    },
+  };
+
+  return pMsg;
+}
+
+static FORCE_INLINE SSyncMessage* syncNewAppendMsg(SyncGroupId groupId, SyncNodeId from,
+                                                  SyncTerm term, SyncIndex logIndex, SyncTerm logTerm,
+                                                  SyncIndex commitIndex, int nEntries, SSyncRaftEntry* entries) {
+  SSyncMessage* pMsg = (SSyncMessage*)malloc(sizeof(SSyncMessage));
+  if (pMsg == NULL) {
+    return NULL;
+  }
+  *pMsg = (SSyncMessage) {
+    .groupId = groupId,
+    .from = from,
+    .term = term,
+    .msgType = RAFT_MSG_APPEND,
+    .appendEntries = (RaftMsg_Append_Entries) {
+      .index = logIndex,
+      .term = logTerm,
+      .commitIndex = commitIndex,
+      .nEntries = nEntries,
+      .entries = entries,
+    },
+  };
+
+  return pMsg;
+}
+
+static FORCE_INLINE SSyncMessage* syncNewEmptyAppendRespMsg(SyncGroupId groupId, SyncNodeId from, SyncTerm term) {
+  SSyncMessage* pMsg = (SSyncMessage*)malloc(sizeof(SSyncMessage));
+  if (pMsg == NULL) {
+    return NULL;
+  }
+  *pMsg = (SSyncMessage) {
+    .groupId = groupId,
+    .from = from,
+    .term = term,
+    .msgType = RAFT_MSG_APPEND_RESP,
+    .appendResp = (RaftMsg_Append_Resp) {
+
+    },
+  };
+
+  return pMsg;
+}
+
+static FORCE_INLINE bool syncIsInternalMsg(RaftMessageType msgType) {
+  return msgType == RAFT_MSG_INTERNAL_PROP ||
+         msgType == RAFT_MSG_INTERNAL_ELECTION;
+}
+
+static FORCE_INLINE bool syncIsPreVoteRespMsg(const SSyncMessage* pMsg) {
+  return pMsg->msgType == RAFT_MSG_VOTE_RESP && pMsg->voteResp.cType == SYNC_RAFT_CAMPAIGN_PRE_ELECTION;
+}
+
+static FORCE_INLINE bool syncIsPreVoteMsg(const SSyncMessage* pMsg) {
+  return pMsg->msgType == RAFT_MSG_VOTE && pMsg->voteResp.cType == SYNC_RAFT_CAMPAIGN_PRE_ELECTION;
+}
+
+void syncFreeMessage(const SSyncMessage* pMsg);
+
+// message handlers
+int syncRaftHandleElectionMessage(SSyncRaft* pRaft, const SSyncMessage* pMsg);
+int syncRaftHandleVoteMessage(SSyncRaft* pRaft, const SSyncMessage* pMsg);
+int syncRaftHandleVoteRespMessage(SSyncRaft* pRaft, const SSyncMessage* pMsg);
+int syncRaftHandleAppendEntriesMessage(SSyncRaft* pRaft, const SSyncMessage* pMsg);
+
+#endif  /* _TD_LIBS_SYNC_RAFT_MESSAGE_H */
\ No newline at end of file

source/libs/sync/inc/raft_replication.h

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef TD_SYNC_RAFT_REPLICATION_H
+#define TD_SYNC_RAFT_REPLICATION_H
+
+#include "sync.h"
+#include "syncInt.h"
+#include "sync_type.h"
+
+int syncRaftReplicate(SSyncRaft* pRaft, int i);
+
+#endif  /* TD_SYNC_RAFT_REPLICATION_H */

source/libs/sync/inc/raft_unstable_log.h

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef TD_SYNC_RAFT_UNSTABLE_LOG_H
+#define TD_SYNC_RAFT_UNSTABLE_LOG_H
+
+#include "sync_type.h"
+
+/* in-memory unstable raft log storage */
+struct SSyncRaftUnstableLog {
+#if 0
+  /* Circular buffer of log entries */
+  RaftEntry *entries;
+
+  /* size of Circular buffer */
+  int size;
+
+  /* Indexes of used slots [front, back) */
+  int front, back;
+
+  /* Index of first entry is offset + 1 */
+  SyncIndex offset;
+
+  /* meta data of snapshot */
+  SSyncRaftUnstableLog snapshot;
+#endif
+};
+
+/**
+ * return index of last in memory log, return 0 if log is empty
+ **/
+//SyncIndex syncRaftLogLastIndex(SSyncRaftUnstableLog* pLog);
+
+#if 0
+void raftLogInit(RaftLog* pLog);
+
+void raftLogClose(RaftLog* pLog);
+
+/**
+ * When startup populating log entrues loaded from disk,
+ * init raft memory log with snapshot index,term and log start idnex.
+ **/ 
+/*
+void raftLogStart(RaftLog* pLog,
+                  RaftSnapshotMeta snapshot,
+                  SyncIndex startIndex);
+*/
+/** 
+ * Get the number of entries the log. 
+ **/
+int raftLogNumEntries(const RaftLog* pLog);
+
+
+
+/**
+ * return last term of in memory log, return 0 if log is empty
+ **/
+SyncTerm raftLogLastTerm(RaftLog* pLog);
+
+/**
+ * return term of log with the given index, return 0 if the term of index cannot be found
+ * , errCode will save the error code.
+ **/
+SyncTerm raftLogTermOf(RaftLog* pLog, SyncIndex index, RaftCode* errCode);
+
+/** 
+ * Get the last index of the most recent snapshot. Return 0 if there are no *
+ * snapshots. 
+ **/
+SyncIndex raftLogSnapshotIndex(RaftLog* pLog);
+
+/* Append a new entry to the log. */
+int raftLogAppend(RaftLog* pLog,
+                  SyncTerm term,
+                  const SSyncBuffer *buf);
+
+/**
+ * acquire log from given index onwards.
+ **/ 
+/*
+int raftLogAcquire(RaftLog* pLog,
+                  SyncIndex index,
+                  RaftEntry **ppEntries,
+                  int *n);
+
+void raftLogRelease(RaftLog* pLog,
+                    SyncIndex index,
+                    RaftEntry *pEntries,
+                    int n);
+*/
+/* Delete all entries from the given index (included) onwards. */
+void raftLogTruncate(RaftLog* pLog, SyncIndex index);
+
+/** 
+ * when taking a new snapshot, the function will update the last snapshot information and delete
+ * all entries up last_index - trailing (included). If the log contains no entry
+ * a last_index - trailing, then no entry will be deleted. 
+ **/
+void raftLogSnapshot(RaftLog* pLog, SyncIndex index, SyncIndex trailing);
+
+#endif
+
+#endif /* TD_SYNC_RAFT_UNSTABLE_LOG_H */
\ No newline at end of file

source/libs/sync/inc/syncInt.h

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _TD_LIBS_SYNC_INT_H
+#define _TD_LIBS_SYNC_INT_H
+
+#include "thash.h"
+#include "os.h"
+#include "sync.h"
+#include "sync_type.h"
+#include "raft.h"
+#include "tlog.h"
+
+#define TAOS_SYNC_MAX_WORKER 3
+
+typedef struct SSyncWorker {
+  pthread_t thread;
+} SSyncWorker;
+
+struct SSyncNode {
+  pthread_mutex_t   mutex;
+  int32_t      refCount;
+  SyncGroupId   vgId;
+  SSyncRaft raft;
+  void* syncTimer;
+};
+
+typedef struct SSyncManager {
+  pthread_mutex_t   mutex;
+
+  // sync server rpc
+  void* serverRpc;
+  // rpc server hash table base on FQDN:port key
+  SHashObj* rpcServerTable;
+
+  // sync client rpc
+  void* clientRpc;
+
+  // worker threads
+  SSyncWorker worker[TAOS_SYNC_MAX_WORKER];
+
+  // vgroup hash table
+  SHashObj* vgroupTable;
+
+  // timer manager
+  void* syncTimerManager;
+
+} SSyncManager;
+
+extern SSyncManager* gSyncManager;
+
+#define syncFatal(...) do { if (sDebugFlag & DEBUG_FATAL) { taosPrintLog("SYNC FATAL ", 255, __VA_ARGS__); }}     while(0)
+#define syncError(...) do { if (sDebugFlag & DEBUG_ERROR) { taosPrintLog("SYNC ERROR ", 255, __VA_ARGS__); }}     while(0)
+#define syncWarn(...)  do { if (sDebugFlag & DEBUG_WARN)  { taosPrintLog("SYNC WARN ", 255, __VA_ARGS__); }}      while(0)
+#define syncInfo(...)  do { if (sDebugFlag & DEBUG_INFO)  { taosPrintLog("SYNC ", 255, __VA_ARGS__); }}           while(0)
+#define syncDebug(...) do { if (sDebugFlag & DEBUG_DEBUG) { taosPrintLog("SYNC ", sDebugFlag, __VA_ARGS__); }} while(0)
+#define syncTrace(...) do { if (sDebugFlag & DEBUG_TRACE) { taosPrintLog("SYNC ", sDebugFlag, __VA_ARGS__); }} while(0)
+
+#endif  /* _TD_LIBS_SYNC_INT_H */
\ No newline at end of file

source/libs/sync/inc/sync_raft_impl.h

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _TD_LIBS_SYNC_RAFT_IMPL_H
+#define _TD_LIBS_SYNC_RAFT_IMPL_H
+
+#include "sync.h"
+#include "sync_type.h"
+#include "raft_message.h"
+#include "sync_raft_quorum.h"
+
+void syncRaftBecomeFollower(SSyncRaft* pRaft, SyncTerm term, SyncNodeId leaderId);
+void syncRaftBecomePreCandidate(SSyncRaft* pRaft);
+void syncRaftBecomeCandidate(SSyncRaft* pRaft);
+void syncRaftBecomeLeader(SSyncRaft* pRaft);
+
+void syncRaftStartElection(SSyncRaft* pRaft, SyncRaftElectionType cType);
+
+void syncRaftTriggerHeartbeat(SSyncRaft* pRaft);
+
+void syncRaftRandomizedElectionTimeout(SSyncRaft* pRaft);
+bool syncRaftIsPromotable(SSyncRaft* pRaft);
+bool syncRaftIsPastElectionTimeout(SSyncRaft* pRaft);
+int  syncRaftQuorum(SSyncRaft* pRaft);
+
+SSyncRaftVoteResult  syncRaftPollVote(SSyncRaft* pRaft, SyncNodeId id, 
+                                    bool preVote, bool accept, 
+                                    int* rejectNum, int *granted);
+
+#endif /* _TD_LIBS_SYNC_RAFT_IMPL_H */

source/libs/sync/inc/sync_raft_inflights.h

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http: *www.gnu.org/licenses/>.
+ */
+
+#ifndef TD_SYNC_RAFT_INFLIGHTS_H
+#define TD_SYNC_RAFT_INFLIGHTS_H
+
+#include "sync.h"
+
+/**
+ * SSyncRaftInflights limits the number of MsgApp (represented by the largest index
+ * contained within) sent to followers but not yet acknowledged by them. Callers
+ * use syncRaftInflightFull() to check whether more messages can be sent, 
+ * call syncRaftInflightAdd() whenever they are sending a new append, 
+ * and release "quota" via FreeLE() whenever an ack is received.
+**/
+typedef struct SSyncRaftInflights {
+  /* the starting index in the buffer */
+  int start;
+
+  /* number of inflights in the buffer */
+  int count;
+
+  /* the size of the buffer */
+  int size;
+
+	/** 
+   * buffer contains the index of the last entry
+	 * inside one message.
+   **/
+  SyncIndex* buffer;
+} SSyncRaftInflights;
+
+SSyncRaftInflights* syncRaftOpenInflights(int size);
+void syncRaftCloseInflights(SSyncRaftInflights*);
+
+static FORCE_INLINE void syncRaftInflightReset(SSyncRaftInflights* inflights) {  
+  inflights->count = 0;
+  inflights->start = 0;
+}
+
+static FORCE_INLINE bool syncRaftInflightFull(SSyncRaftInflights* inflights) {
+  return inflights->count == inflights->size;
+}
+
+/**
+ * syncRaftInflightAdd notifies the Inflights that a new message with the given index is being
+ * dispatched. syncRaftInflightFull() must be called prior to syncRaftInflightAdd() 
+ * to verify that there is room for one more message, 
+ * and consecutive calls to add syncRaftInflightAdd() must provide a
+ * monotonic sequence of indexes.
+ **/
+void syncRaftInflightAdd(SSyncRaftInflights* inflights, SyncIndex inflightIndex);
+
+/**
+ * syncRaftInflightFreeLE frees the inflights smaller or equal to the given `to` flight.
+ **/
+void syncRaftInflightFreeLE(SSyncRaftInflights* inflights, SyncIndex toIndex);
+
+/** 
+ * syncRaftInflightFreeFirstOne releases the first inflight. 
+ * This is a no-op if nothing is inflight.
+ **/
+void syncRaftInflightFreeFirstOne(SSyncRaftInflights* inflights);
+
+#endif /* TD_SYNC_RAFT_INFLIGHTS_H */
\ No newline at end of file

source/libs/sync/inc/sync_raft_progress.h

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http: *www.gnu.org/licenses/>.
+ */
+
+#ifndef TD_SYNC_RAFT_PROGRESS_H
+#define TD_SYNC_RAFT_PROGRESS_H
+
+#include "sync_type.h"
+#include "sync_raft_inflights.h"
+
+/** 
+ * State defines how the leader should interact with the follower.
+ *
+ * When in PROGRESS_STATE_PROBE, leader sends at most one replication message
+ * per heartbeat interval. It also probes actual progress of the follower.
+ * 
+ * When in PROGRESS_STATE_REPLICATE, leader optimistically increases next
+ * to the latest entry sent after sending replication message. This is
+ * an optimized state for fast replicating log entries to the follower.
+ *
+ * When in PROGRESS_STATE_SNAPSHOT, leader should have sent out snapshot
+ * before and stops sending any replication message.
+ * 
+ * PROGRESS_STATE_PROBE is the initial state.
+ **/
+typedef enum RaftProgressState {
+  /**
+	* StateProbe indicates a follower whose last index isn't known. Such a
+	* follower is "probed" (i.e. an append sent periodically) to narrow down
+	* its last index. In the ideal (and common) case, only one round of probing
+	* is necessary as the follower will react with a hint. Followers that are
+	* probed over extended periods of time are often offline.
+  **/
+  PROGRESS_STATE_PROBE = 0,
+
+  /**
+	* StateReplicate is the state steady in which a follower eagerly receives
+	* log entries to append to its log.
+  **/
+  PROGRESS_STATE_REPLICATE,
+
+  /**
+	* StateSnapshot indicates a follower that needs log entries not available
+	* from the leader's Raft log. Such a follower needs a full snapshot to
+	* return to StateReplicate.
+  **/
+  PROGRESS_STATE_SNAPSHOT,
+} RaftProgressState;
+
+/**
+ * Progress represents a follower’s progress in the view of the leader. Leader maintains
+ * progresses of all followers, and sends entries to the follower based on its progress.
+ **/
+struct SSyncRaftProgress {
+	SyncNodeId id;
+
+  SyncIndex nextIndex;
+
+  SyncIndex matchIndex;
+
+  /**
+	* State defines how the leader should interact with the follower.
+	*
+	* When in StateProbe, leader sends at most one replication message
+	* per heartbeat interval. It also probes actual progress of the follower.
+	*
+	* When in StateReplicate, leader optimistically increases next
+	* to the latest entry sent after sending replication message. This is
+	* an optimized state for fast replicating log entries to the follower.
+	*
+	* When in StateSnapshot, leader should have sent out snapshot
+	* before and stops sending any replication message.
+  **/
+  RaftProgressState state;
+
+	/** 
+   * pendingSnapshotIndex is used in PROGRESS_STATE_SNAPSHOT.
+	 * If there is a pending snapshot, the pendingSnapshotIndex will be set to the
+	 * index of the snapshot. If pendingSnapshotIndex is set, the replication process of
+	 * this Progress will be paused. raft will not resend snapshot until the pending one
+	 * is reported to be failed.
+   **/
+  SyncIndex pendingSnapshotIndex;
+
+	/** 
+   * recentActive is true if the progress is recently active. Receiving any messages
+   * from the corresponding follower indicates the progress is active.
+	 * RecentActive can be reset to false after an election timeout.
+   **/
+  bool recentActive;
+
+  /**
+	* probeSent is used while this follower is in StateProbe. When probeSent is
+	* true, raft should pause sending replication message to this peer until
+	* probeSent is reset. See ProbeAcked() and IsPaused().
+  **/
+	bool probeSent;
+
+  /**
+	 * inflights is a sliding window for the inflight messages.
+	 * Each inflight message contains one or more log entries.
+	 * The max number of entries per message is defined in raft config as MaxSizePerMsg.
+	 * Thus inflight effectively limits both the number of inflight messages
+	 * and the bandwidth each Progress can use.
+	 * When inflights is Full, no more message should be sent.
+	 * When a leader sends out a message, the index of the last
+	 * entry should be added to inflights. The index MUST be added
+	 * into inflights in order.
+	 * When a leader receives a reply, the previous inflights should
+	 * be freed by calling inflights.FreeLE with the index of the last
+	 * received entry.
+  **/
+  SSyncRaftInflights* inflights;
+
+  /**
+   *  IsLearner is true if this progress is tracked for a learner.
+   **/
+  bool isLearner;
+};
+
+void syncRaftInitProgress(int i, SSyncRaft* pRaft, SSyncRaftProgress* progress);
+
+/**
+ * syncRaftProgressBecomeProbe transitions into StateProbe. Next is reset to Match+1 or,
+ * optionally and if larger, the index of the pending snapshot.
+ **/
+void syncRaftProgressBecomeProbe(SSyncRaftProgress* progress);
+
+/**
+ * syncRaftProgressBecomeReplicate transitions into StateReplicate, resetting Next to Match+1.
+ **/ 
+void syncRaftProgressBecomeReplicate(SSyncRaftProgress* progress);
+
+/**
+ * syncRaftProgressMaybeUpdate is called when an MsgAppResp arrives from the follower, with the
+ * index acked by it. The method returns false if the given n index comes from
+ * an outdated message. Otherwise it updates the progress and returns true.
+ **/
+bool syncRaftProgressMaybeUpdate(SSyncRaftProgress* progress, SyncIndex lastIndex);
+
+/**
+ * syncRaftProgressOptimisticNextIndex signals that appends all the way up to and including index n
+ * are in-flight. As a result, Next is increased to n+1.
+ **/
+static FORCE_INLINE void syncRaftProgressOptimisticNextIndex(SSyncRaftProgress* progress, SyncIndex nextIndex) {
+  progress->nextIndex = nextIndex + 1;
+}
+
+/**
+ * syncRaftProgressMaybeDecrTo adjusts the Progress to the receipt of a MsgApp rejection. The
+ * arguments are the index of the append message rejected by the follower, and
+ * the hint that we want to decrease to.
+ *
+ * Rejections can happen spuriously as messages are sent out of order or
+ * duplicated. In such cases, the rejection pertains to an index that the
+ * Progress already knows were previously acknowledged, and false is returned
+ * without changing the Progress.
+ *
+ * If the rejection is genuine, Next is lowered sensibly, and the Progress is
+ * cleared for sending log entries.
+**/
+bool syncRaftProgressMaybeDecrTo(SSyncRaftProgress* progress,
+                                SyncIndex rejected, SyncIndex matchHint);
+
+/**
+ * syncRaftProgressIsPaused returns whether sending log entries to this node has been throttled.
+ * This is done when a node has rejected recent MsgApps, is currently waiting
+ * for a snapshot, or has reached the MaxInflightMsgs limit. In normal
+ * operation, this is false. A throttled node will be contacted less frequently
+ * until it has reached a state in which it's able to accept a steady stream of
+ * log entries again.
+ **/
+bool syncRaftProgressIsPaused(SSyncRaftProgress* progress);
+
+static FORCE_INLINE SyncIndex syncRaftProgressNextIndex(SSyncRaftProgress* progress) {
+  return progress->nextIndex;
+}
+
+static FORCE_INLINE RaftProgressState syncRaftProgressInReplicate(SSyncRaftProgress* progress) {
+  return progress->state == PROGRESS_STATE_REPLICATE;
+}
+
+static FORCE_INLINE RaftProgressState syncRaftProgressInSnapshot(SSyncRaftProgress* progress) {
+  return progress->state == PROGRESS_STATE_SNAPSHOT;
+}
+
+static FORCE_INLINE RaftProgressState syncRaftProgressInProbe(SSyncRaftProgress* progress) {
+  return progress->state == PROGRESS_STATE_PROBE;
+}
+
+static FORCE_INLINE bool syncRaftProgressRecentActive(SSyncRaftProgress* progress) {
+  return progress->recentActive;
+}
+
+/** 
+ * return true if progress's log is up-todate
+ **/
+bool syncRaftProgressIsUptodate(SSyncRaft* pRaft, SSyncRaftProgress* progress);
+
+void syncRaftProgressBecomeSnapshot(SSyncRaftProgress* progress, SyncIndex snapshotIndex);
+
+
+
+#if 0
+
+void syncRaftProgressAbortSnapshot(SSyncRaft* pRaft, int i);
+
+
+
+SyncIndex syncRaftProgressMatchIndex(SSyncRaft* pRaft, int i);
+
+void syncRaftProgressUpdateLastSend(SSyncRaft* pRaft, int i);
+
+void syncRaftProgressUpdateSnapshotLastSend(SSyncRaft* pRaft, int i);
+
+bool syncRaftProgressResetRecentRecv(SSyncRaft* pRaft, int i);
+
+void syncRaftProgressMarkRecentRecv(SSyncRaft* pRaft, int i);
+
+
+
+void syncRaftProgressAbortSnapshot(SSyncRaft* pRaft, int i);
+
+#endif
+
+#endif /* TD_SYNC_RAFT_PROGRESS_H */
\ No newline at end of file

source/libs/sync/inc/sync_raft_progress_tracker.h

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _TD_LIBS_SYNC_RAFT_PROGRESS_TRACKER_H
+#define _TD_LIBS_SYNC_RAFT_PROGRESS_TRACKER_H
+
+#include "sync_type.h"
+#include "sync_raft_quorum_joint.h"
+#include "sync_raft_progress.h"
+
+struct SSyncRaftProgressTrackerConfig {
+  SSyncRaftQuorumJointConfig voters;
+
+	/** 
+	 * autoLeave is true if the configuration is joint and a transition to the
+	 * incoming configuration should be carried out automatically by Raft when
+	 * this is possible. If false, the configuration will be joint until the
+	 * application initiates the transition manually.
+   **/
+  bool autoLeave;
+
+	/** 
+   * Learners is a set of IDs corresponding to the learners active in the
+	 * current configuration.
+   * 
+	 * Invariant: Learners and Voters does not intersect, i.e. if a peer is in
+	 * either half of the joint config, it can't be a learner; if it is a
+	 * learner it can't be in either half of the joint config. This invariant
+	 * simplifies the implementation since it allows peers to have clarity about
+	 * its current role without taking into account joint consensus.
+   **/
+  SyncNodeId learners[TSDB_MAX_REPLICA];
+
+  /**
+   *  When we turn a voter into a learner during a joint consensus transition,
+	 * we cannot add the learner directly when entering the joint state. This is
+	 * because this would violate the invariant that the intersection of
+	 * voters and learners is empty. For example, assume a Voter is removed and
+	 * immediately re-added as a learner (or in other words, it is demoted):
+   * 
+	 * Initially, the configuration will be
+   * 
+	 *   voters:   {1 2 3}
+	 *   learners: {}
+   * 
+	 * and we want to demote 3. Entering the joint configuration, we naively get
+   * 
+	 *   voters:   {1 2} & {1 2 3}
+	 *   learners: {3}
+   * 
+	 * but this violates the invariant (3 is both voter and learner). Instead,
+	 * we get
+   * 
+	 *   voters:   {1 2} & {1 2 3}
+	 *   learners: {}
+	 *   next_learners: {3}
+   * 
+	 * Where 3 is now still purely a voter, but we are remembering the intention
+	 * to make it a learner upon transitioning into the final configuration:
+   * 
+	 *   voters:   {1 2}
+	 *   learners: {3}
+	 *   next_learners: {}
+   * 
+	 * Note that next_learners is not used while adding a learner that is not
+	 * also a voter in the joint config. In this case, the learner is added
+	 * right away when entering the joint configuration, so that it is caught up
+	 * as soon as possible.
+   **/
+  SyncNodeId learnersNext[TSDB_MAX_REPLICA];
+};
+
+struct SSyncRaftProgressTracker {
+  SSyncRaftProgressTrackerConfig config;
+
+  SSyncRaftProgress progressMap[TSDB_MAX_REPLICA];
+
+	SyncRaftVoteResult votes[TSDB_MAX_REPLICA];
+  int maxInflight;
+};
+
+SSyncRaftProgressTracker* syncRaftOpenProgressTracker();
+
+void syncRaftResetVotes(SSyncRaftProgressTracker*);
+
+typedef void (*visitProgressFp)(int i, SSyncRaftProgress* progress, void* arg);
+void syncRaftProgressVisit(SSyncRaftProgressTracker*, visitProgressFp visit, void* arg);
+
+/**
+ * syncRaftRecordVote records that the node with the given id voted for this Raft
+ * instance if v == true (and declined it otherwise).
+ **/
+void syncRaftRecordVote(SSyncRaftProgressTracker* tracker, int i, bool grant);
+
+/** 
+ * syncRaftTallyVotes returns the number of granted and rejected Votes, and whether the
+ * election outcome is known.
+ **/
+SyncRaftVoteResult syncRaftTallyVotes(SSyncRaftProgressTracker* tracker, int* rejected, int *granted);
+
+#endif  /* _TD_LIBS_SYNC_RAFT_PROGRESS_TRACKER_H */

source/libs/sync/inc/sync_raft_quorum.h

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef TD_SYNC_RAFT_QUORUM_H
+#define TD_SYNC_RAFT_QUORUM_H
+
+/**
+ * SSyncRaftVoteResult indicates the outcome of a vote.
+ **/
+typedef enum {
+	/**
+	 *  SYNC_RAFT_VOTE_PENDING indicates that the decision of the vote depends on future
+	 * votes, i.e. neither "yes" or "no" has reached quorum yet.
+	 **/
+	SYNC_RAFT_VOTE_PENDING = 1,
+
+	/** 
+	 * SYNC_RAFT_VOTE_LOST indicates that the quorum has voted "no".
+	 **/
+	SYNC_RAFT_VOTE_LOST = 2,
+
+	/** 
+	 * SYNC_RAFT_VOTE_WON indicates that the quorum has voted "yes".
+	 **/
+	SYNC_RAFT_VOTE_WON = 3,
+} SSyncRaftVoteResult;
+
+#endif /* TD_SYNC_RAFT_QUORUM_H */
\ No newline at end of file

source/libs/sync/inc/sync_raft_quorum_joint.h

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _TD_LIBS_SYNC_RAFT_QUORUM_JOINT_H
+#define _TD_LIBS_SYNC_RAFT_QUORUM_JOINT_H
+
+#include "taosdef.h"
+#include "sync.h"
+#include "sync_type.h"
+
+/**
+ * SSyncRaftQuorumJointConfig is a configuration of two groups of (possibly overlapping)
+ * majority configurations. Decisions require the support of both majorities.
+ **/
+typedef struct SSyncRaftQuorumJointConfig {
+  SSyncCluster majorityConfig[2];
+}SSyncRaftQuorumJointConfig;
+
+/**
+ * syncRaftVoteResult takes a mapping of voters to yes/no (true/false) votes and returns
+ * a result indicating whether the vote is pending, lost, or won. A joint quorum
+ * requires both majority quorums to vote in favor.
+ **/
+SyncRaftVoteResult syncRaftVoteResult(SSyncRaftQuorumJointConfig* config, const SyncRaftVoteResult* votes);
+
+#endif /* _TD_LIBS_SYNC_RAFT_QUORUM_JOINT_H */

source/libs/sync/inc/sync_raft_quorum_majority.h

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _TD_LIBS_SYNC_RAFT_QUORUM_MAJORITY_H
+#define _TD_LIBS_SYNC_RAFT_QUORUM_MAJORITY_H
+
+#include "sync.h"
+#include "sync_type.h"
+
+/**
+ * syncRaftMajorityVoteResult takes a mapping of voters to yes/no (true/false) votes and returns
+ * a result indicating whether the vote is pending (i.e. neither a quorum of
+ * yes/no has been reached), won (a quorum of yes has been reached), or lost (a
+ * quorum of no has been reached).
+ **/
+SyncRaftVoteResult syncRaftMajorityVoteResult(SSyncCluster* config, const SyncRaftVoteResult* votes);
+
+#endif /* _TD_LIBS_SYNC_RAFT_QUORUM_MAJORITY_H */

source/libs/sync/inc/sync_type.h

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _TD_LIBS_SYNC_TYPE_H
+#define _TD_LIBS_SYNC_TYPE_H
+
+#include <stdint.h>
+#include "osMath.h"
+
+#define SYNC_NON_NODE_ID -1
+#define SYNC_NON_TERM     0
+
+typedef int32_t SyncTime;
+typedef uint32_t SyncTick;
+
+typedef struct SSyncRaft SSyncRaft;
+
+typedef struct SSyncRaftProgress SSyncRaftProgress;
+typedef struct SSyncRaftProgressTrackerConfig SSyncRaftProgressTrackerConfig;
+
+typedef struct SSyncRaftProgressTracker SSyncRaftProgressTracker;
+
+typedef struct SSyncRaftLog SSyncRaftLog;
+
+typedef struct SSyncRaftEntry SSyncRaftEntry;
+
+#if 0
+#ifndef MIN
+#define MIN(x, y) (((x) < (y)) ? (x) : (y))
+#endif
+
+#ifndef MAX
+#define MAX(x, y) (((x) > (y)) ? (x) : (y))
+#endif
+#endif
+
+typedef enum {
+  SYNC_RAFT_CAMPAIGN_PRE_ELECTION = 0,
+  SYNC_RAFT_CAMPAIGN_ELECTION     = 1,
+  SYNC_RAFT_CAMPAIGN_TRANSFER     = 2,
+} SyncRaftElectionType;
+
+typedef enum {
+  // the init vote resp status
+  SYNC_RAFT_VOTE_RESP_UNKNOWN = 0,
+
+  // grant the vote request
+  SYNC_RAFT_VOTE_RESP_GRANT   = 1,
+
+  //reject the vote request
+  SYNC_RAFT_VOTE_RESP_REJECT  = 2,
+} SyncRaftVoteResult;
+
+#endif  /* _TD_LIBS_SYNC_TYPE_H */

source/libs/sync/src/raft.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "raft.h"
+#include "raft_configuration.h"
+#include "raft_log.h"
+#include "raft_replication.h"
+#include "sync_raft_progress_tracker.h"
+#include "syncInt.h"
+
+#define RAFT_READ_LOG_MAX_NUM 100
+
+static bool preHandleMessage(SSyncRaft* pRaft, const SSyncMessage* pMsg);
+static bool preHandleNewTermMessage(SSyncRaft* pRaft, const SSyncMessage* pMsg);
+static bool preHandleOldTermMessage(SSyncRaft* pRaft, const SSyncMessage* pMsg);
+
+int32_t syncRaftStart(SSyncRaft* pRaft, const SSyncInfo* pInfo) {
+  SSyncNode* pNode = pRaft->pNode;
+  SSyncServerState serverState;
+  SStateManager* stateManager;
+  SSyncLogStore* logStore;
+  SSyncFSM* fsm;
+  SyncIndex initIndex = pInfo->snapshotIndex;
+  SSyncBuffer buffer[RAFT_READ_LOG_MAX_NUM];
+  int nBuf, limit, i;
+  
+  memset(pRaft, 0, sizeof(SSyncRaft));
+
+  memcpy(&pRaft->fsm, &pInfo->fsm, sizeof(SSyncFSM));
+  memcpy(&pRaft->logStore, &pInfo->logStore, sizeof(SSyncLogStore));
+  memcpy(&pRaft->stateManager, &pInfo->stateManager, sizeof(SStateManager));
+
+  stateManager = &(pRaft->stateManager);
+  logStore = &(pRaft->logStore);
+  fsm = &(pRaft->fsm);
+
+  // init progress tracker
+  pRaft->tracker = syncRaftOpenProgressTracker();
+  if (pRaft->tracker == NULL) {
+    return -1;
+  }
+
+  // open raft log
+  if ((pRaft->log = syncRaftLogOpen()) == NULL) {
+    return -1;
+  }
+  // read server state
+  if (stateManager->readServerState(stateManager, &serverState) != 0) {
+    syncError("readServerState for vgid %d fail", pInfo->vgId);
+    return -1;
+  }
+  assert(initIndex <= serverState.commitIndex);
+
+  // restore fsm state from snapshot index + 1 until commitIndex
+  ++initIndex;
+  while (initIndex <= serverState.commitIndex) {
+    limit = MIN(RAFT_READ_LOG_MAX_NUM, serverState.commitIndex - initIndex + 1);
+
+    if (logStore->logRead(logStore, initIndex, limit, buffer, &nBuf) != 0) {
+      return -1;
+    }
+    assert(limit == nBuf);
+  
+    for (i = 0; i < limit; ++i) {
+      fsm->applyLog(fsm, initIndex + i, &(buffer[i]), NULL);
+      free(buffer[i].data);
+    }
+    initIndex += nBuf;
+  }
+  assert(initIndex == serverState.commitIndex);
+
+  //pRaft->heartbeatTimeoutTick = 1;
+
+  syncRaftBecomeFollower(pRaft, pRaft->term, SYNC_NON_NODE_ID);
+
+  pRaft->selfIndex = pRaft->cluster.selfIndex;
+
+  syncInfo("[%d:%d] restore vgid %d state: snapshot index success", 
+    pRaft->selfGroupId, pRaft->selfId, pInfo->vgId);
+  return 0;
+}
+
+int32_t syncRaftStep(SSyncRaft* pRaft, const SSyncMessage* pMsg) {
+  syncDebug("from %d, type:%d, term:%" PRId64 ", state:%d",
+    pMsg->from, pMsg->msgType, pMsg->term, pRaft->state);
+
+  if (preHandleMessage(pRaft, pMsg)) {
+    syncFreeMessage(pMsg);
+    return 0;
+  }
+
+  RaftMessageType msgType = pMsg->msgType;
+  if (msgType == RAFT_MSG_INTERNAL_ELECTION) {
+    syncRaftHandleElectionMessage(pRaft, pMsg);
+  } else if (msgType == RAFT_MSG_VOTE) {
+    syncRaftHandleVoteMessage(pRaft, pMsg);
+  } else {
+    pRaft->stepFp(pRaft, pMsg);
+  }
+
+  syncFreeMessage(pMsg);
+  return 0;
+}
+
+int32_t syncRaftTick(SSyncRaft* pRaft) {
+  pRaft->currentTick += 1;
+  return 0;
+}
+
+/**
+ * pre-handle message, return true means no need to continue
+ * Handle the message term, which may result in our stepping down to a follower.
+ **/
+static bool preHandleMessage(SSyncRaft* pRaft, const SSyncMessage* pMsg) {
+  // local message?
+  if (pMsg->term == 0) {
+    return false;
+  }
+
+  if (pMsg->term > pRaft->term) {
+    return preHandleNewTermMessage(pRaft, pMsg);
+  } else if (pMsg->term < pRaft->term) {
+    return preHandleOldTermMessage(pRaft, pMsg);
+  }
+
+  return false;
+}
+
+static bool preHandleNewTermMessage(SSyncRaft* pRaft, const SSyncMessage* pMsg) {
+  SyncNodeId leaderId = pMsg->from;
+  RaftMessageType msgType = pMsg->msgType;
+
+  if (msgType == RAFT_MSG_VOTE) {
+    // TODO
+    leaderId = SYNC_NON_NODE_ID;
+  }
+
+  if (syncIsPreVoteMsg(pMsg)) {
+    // Never change our term in response to a PreVote
+  } else if (syncIsPreVoteRespMsg(pMsg) && !pMsg->voteResp.rejected) {
+		/**
+     * We send pre-vote requests with a term in our future. If the
+		 * pre-vote is granted, we will increment our term when we get a
+		 * quorum. If it is not, the term comes from the node that
+		 * rejected our vote so we should become a follower at the new
+		 * term.
+     **/
+  } else {
+    syncInfo("[%d:%d] [term:%" PRId64 "] received a %d message with higher term from %d [term:%" PRId64 "]",
+      pRaft->selfGroupId, pRaft->selfId, pRaft->term, msgType, pMsg->from, pMsg->term);
+    syncRaftBecomeFollower(pRaft, pMsg->term, leaderId);
+  }
+
+  return false;
+}
+
+static bool preHandleOldTermMessage(SSyncRaft* pRaft, const SSyncMessage* pMsg) {
+  if (pRaft->checkQuorum && pMsg->msgType == RAFT_MSG_APPEND) {
+		/**
+     * We have received messages from a leader at a lower term. It is possible
+		 * that these messages were simply delayed in the network, but this could
+		 * also mean that this node has advanced its term number during a network
+		 * partition, and it is now unable to either win an election or to rejoin
+	   * the majority on the old term. If checkQuorum is false, this will be
+		 * handled by incrementing term numbers in response to MsgVote with a
+		 * higher term, but if checkQuorum is true we may not advance the term on
+		 * MsgVote and must generate other messages to advance the term. The net
+		 * result of these two features is to minimize the disruption caused by
+		 * nodes that have been removed from the cluster's configuration: a
+		 * removed node will send MsgVotes (or MsgPreVotes) which will be ignored,
+		 * but it will not receive MsgApp or MsgHeartbeat, so it will not create
+		 * disruptive term increases
+    **/
+    int peerIndex = syncRaftConfigurationIndexOfNode(pRaft, pMsg->from);
+    if (peerIndex < 0) {
+      return true;
+    }
+    SSyncMessage* msg = syncNewEmptyAppendRespMsg(pRaft->selfGroupId, pRaft->selfId, pRaft->term);
+    if (msg == NULL) {
+      return true;
+    }
+
+    pRaft->io.send(msg, &(pRaft->cluster.nodeInfo[peerIndex]));
+  } else {
+    // ignore other cases
+    syncInfo("[%d:%d] [term:%" PRId64 "] ignored a %d message with lower term from %d [term:%" PRId64 "]",
+      pRaft->selfGroupId, pRaft->selfId, pRaft->term, pMsg->msgType, pMsg->from, pMsg->term);    
+  }
+
+  return true;
+}
\ No newline at end of file

source/libs/sync/src/raft_configuration.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "raft_configuration.h"
+#include "raft.h"
+
+int syncRaftConfigurationIndexOfNode(SSyncRaft *pRaft, SyncNodeId id) {
+  return (int)(id);
+}
+
+int syncRaftConfigurationVoterCount(SSyncRaft *pRaft) {
+  return pRaft->cluster.replica;
+}
\ No newline at end of file

source/libs/sync/src/raft_election.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "syncInt.h"
+#include "raft.h"
+#include "raft_log.h"
+#include "raft_message.h"
+
+void syncRaftStartElection(SSyncRaft* pRaft, SyncRaftElectionType cType) {
+  SyncTerm term;
+  bool preVote;
+  RaftMessageType voteMsgType;
+
+  if (syncRaftIsPromotable(pRaft)) {
+    syncDebug("[%d:%d] is unpromotable; campaign() should have been called", pRaft->selfGroupId, pRaft->selfId);
+    return 0;
+  }
+
+  if (cType == SYNC_RAFT_CAMPAIGN_PRE_ELECTION) {
+    syncRaftBecomePreCandidate(pRaft);
+    preVote = true;
+    // PreVote RPCs are sent for the next term before we've incremented r.Term.
+    term = pRaft->term + 1;
+  } else {
+    syncRaftBecomeCandidate(pRaft);
+    voteMsgType = RAFT_MSG_VOTE;
+    term = pRaft->term;
+    preVote = false;
+  }
+
+  int quorum = syncRaftQuorum(pRaft);
+  SSyncRaftVoteResult result = syncRaftPollVote(pRaft, pRaft->selfId, preVote, true, NULL, NULL);
+  if (result == SYNC_RAFT_VOTE_WON) {
+		/**
+     * We won the election after voting for ourselves (which must mean that
+		 * this is a single-node cluster). Advance to the next state.
+     **/
+    if (cType == SYNC_RAFT_CAMPAIGN_PRE_ELECTION) {
+      syncRaftStartElection(pRaft, SYNC_RAFT_CAMPAIGN_ELECTION);
+    } else {
+      syncRaftBecomeLeader(pRaft);
+    }
+    return;
+  }
+
+  // broadcast vote message to other peers
+  int i;
+  SyncIndex lastIndex = syncRaftLogLastIndex(pRaft->log);
+  SyncTerm lastTerm = syncRaftLogLastTerm(pRaft->log);
+  for (i = 0; i < pRaft->cluster.replica; ++i) {
+    if (i == pRaft->cluster.selfIndex) {
+      continue;
+    }
+
+    SyncNodeId nodeId = pRaft->cluster.nodeInfo[i].nodeId;
+
+    SSyncMessage* pMsg = syncNewVoteMsg(pRaft->selfGroupId, pRaft->selfId, 
+                                        term, cType, lastIndex, lastTerm);
+    if (pMsg == NULL) {
+      continue;
+    }
+
+    syncInfo("[%d:%d] [logterm: %" PRId64 ", index: %" PRId64 "] sent %d request to %d at term %" PRId64 "", 
+      pRaft->selfGroupId, pRaft->selfId, lastTerm, 
+      lastIndex, voteMsgType, nodeId, pRaft->term);
+
+    pRaft->io.send(pMsg, &(pRaft->cluster.nodeInfo[i]));
+  }
+}
\ No newline at end of file

source/libs/sync/src/raft_handle_append_entries_message.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "syncInt.h"
+#include "raft.h"
+#include "raft_log.h"
+#include "raft_configuration.h"
+#include "raft_message.h"
+
+int syncRaftHandleAppendEntriesMessage(SSyncRaft* pRaft, const SSyncMessage* pMsg) {
+  const RaftMsg_Append_Entries *appendEntries = &(pMsg->appendEntries);
+  
+  int peerIndex = syncRaftConfigurationIndexOfNode(pRaft, pMsg->from);
+  
+  if (peerIndex < 0) {
+    return 0;
+  }
+
+  SSyncMessage* pRespMsg = syncNewEmptyAppendRespMsg(pRaft->selfGroupId, pRaft->selfId, pRaft->term);
+  if (pRespMsg == NULL) {
+    return 0;
+  }
+
+  RaftMsg_Append_Entries *appendResp = &(pRespMsg->appendResp);
+  // ignore committed logs
+  if (syncRaftLogIsCommitted(pRaft->log, appendEntries->index)) {
+    appendResp->index = pRaft->log->commitIndex;
+    goto out;
+  }
+
+  syncInfo("[%d:%d] recv append from %d index %" PRId64"",
+      pRaft->selfGroupId, pRaft->selfId, pMsg->from, appendEntries->index); 
+
+out:
+  pRaft->io.send(pRespMsg, &(pRaft->cluster.nodeInfo[peerIndex]));
+  return 0;
+}
\ No newline at end of file

source/libs/sync/src/raft_handle_election_message.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "syncInt.h"
+#include "raft.h"
+#include "raft_log.h"
+#include "raft_message.h"
+
+int syncRaftHandleElectionMessage(SSyncRaft* pRaft, const SSyncMessage* pMsg) {
+  if (pRaft->state == TAOS_SYNC_ROLE_LEADER) {
+    syncDebug("[%d:%d] ignoring RAFT_MSG_INTERNAL_ELECTION because already leader", pRaft->selfGroupId, pRaft->selfId);
+    return 0;
+  }
+
+  if (!syncRaftIsPromotable(pRaft)) {
+    syncDebug("[%d:%d] is unpromotable and can not campaign", pRaft->selfGroupId, pRaft->selfId);
+    return 0;
+  }
+  // if there is pending uncommitted config,cannot start election
+  if (syncRaftLogNumOfPendingConf(pRaft->log) > 0 && syncRaftHasUnappliedLog(pRaft->log)) {
+    syncWarn("[%d:%d] cannot syncRaftStartElection at term %" PRId64 " since there are still pending configuration changes to apply",
+      pRaft->selfGroupId, pRaft->selfId, pRaft->term);
+    return 0;
+  }
+
+  syncInfo("[%d:%d] is starting a new election at term %" PRId64 "", pRaft->selfGroupId, pRaft->selfId, pRaft->term);
+
+  if (pRaft->preVote) {
+    syncRaftStartElection(pRaft, SYNC_RAFT_CAMPAIGN_PRE_ELECTION);
+  } else {
+    syncRaftStartElection(pRaft, SYNC_RAFT_CAMPAIGN_ELECTION);
+  }
+
+  return 0;
+}

source/libs/sync/src/raft_handle_vote_message.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "syncInt.h"
+#include "raft.h"
+#include "raft_configuration.h"
+#include "raft_log.h"
+#include "raft_message.h"
+
+static bool canGrantVoteMessage(SSyncRaft* pRaft, const SSyncMessage* pMsg);
+
+int syncRaftHandleVoteMessage(SSyncRaft* pRaft, const SSyncMessage* pMsg) {
+  SSyncMessage* pRespMsg;
+  int voteIndex = syncRaftConfigurationIndexOfNode(pRaft, pMsg->from);
+  if (voteIndex == -1) {
+    return 0;
+  }
+  bool grant;
+  SyncIndex lastIndex = syncRaftLogLastIndex(pRaft->log);
+  SyncTerm lastTerm = syncRaftLogLastTerm(pRaft->log);
+
+  grant = canGrantVoteMessage(pRaft, pMsg);
+  pRespMsg = syncNewVoteRespMsg(pRaft->selfGroupId, pRaft->selfId, pMsg->vote.cType, !grant);
+  if (pRespMsg == NULL) {
+    return 0;
+  }
+  syncInfo("[%d:%d] [logterm: %" PRId64 ", index: %" PRId64 ", vote: %d] %s for %d"\    
+    "[logterm: %" PRId64 ", index: %" PRId64 "] at term %" PRId64 "",
+    pRaft->selfGroupId, pRaft->selfId, lastTerm, lastIndex, pRaft->voteFor,
+    grant ? "grant" : "reject",
+    pMsg->from, pMsg->vote.lastTerm, pMsg->vote.lastIndex, pRaft->term);
+
+  pRaft->io.send(pRespMsg, &(pRaft->cluster.nodeInfo[voteIndex]));
+  return 0;
+}
+
+static bool canGrantVoteMessage(SSyncRaft* pRaft, const SSyncMessage* pMsg) {
+  if (!(pRaft->voteFor == SYNC_NON_NODE_ID || pMsg->term > pRaft->term || pRaft->voteFor == pMsg->from)) {
+    return false;
+  }
+  if (!syncRaftLogIsUptodate(pRaft->log, pMsg->vote.lastIndex, pMsg->vote.lastTerm)) {
+    return false;
+  }
+
+  return true;
+}
\ No newline at end of file

source/libs/sync/src/raft_handle_vote_resp_message.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "syncInt.h"
+#include "raft.h"
+#include "raft_configuration.h"
+#include "raft_message.h"
+
+int syncRaftHandleVoteRespMessage(SSyncRaft* pRaft, const SSyncMessage* pMsg) {
+  int granted, rejected;
+  int quorum;
+  int voterIndex;
+
+  assert(pRaft->state == TAOS_SYNC_ROLE_CANDIDATE);
+
+  voterIndex = syncRaftConfigurationIndexOfNode(pRaft, pMsg->from);
+  if (voterIndex == -1) {
+    syncError("[%d:%d] recv vote resp from unknown server %d", pRaft->selfGroupId, pRaft->selfId, pMsg->from);
+    return 0;
+  }
+
+  if (pRaft->state != TAOS_SYNC_ROLE_CANDIDATE) {
+    syncError("[%d:%d] is not candidate, ignore vote resp", pRaft->selfGroupId, pRaft->selfId);
+    return 0;
+  }
+
+  SSyncRaftVoteResult result = syncRaftPollVote(pRaft, pMsg->from, 
+                                pMsg->voteResp.cType == SYNC_RAFT_CAMPAIGN_PRE_ELECTION,
+                                !pMsg->voteResp.rejected, &rejected, &granted);
+
+  syncInfo("[%d:%d] [quorum:%d] has received %d votes and %d vote rejections",
+    pRaft->selfGroupId, pRaft->selfId, quorum, granted, rejected);
+
+  if (result == SYNC_RAFT_VOTE_WON) {
+    if (pRaft->candidateState.inPreVote) {
+      syncRaftStartElection(pRaft, SYNC_RAFT_CAMPAIGN_ELECTION);
+    } else {
+      syncRaftBecomeLeader(pRaft);
+
+    }
+  } else if (result == SYNC_RAFT_VOTE_LOST) {
+    syncRaftBecomeFollower(pRaft, pRaft->term, SYNC_NON_NODE_ID);
+  }
+
+  return 0;
+}
\ No newline at end of file

source/libs/sync/src/raft_log.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "raft_log.h"
+
+SSyncRaftLog* syncRaftLogOpen() {
+  return NULL;
+}
+
+SyncIndex syncRaftLogLastIndex(SSyncRaftLog* pLog) {
+  return 0;
+}
+
+SyncIndex syncRaftLogSnapshotIndex(SSyncRaftLog* pLog) {
+  return 0;
+}
+
+SyncTerm syncRaftLogLastTerm(SSyncRaftLog* pLog) {
+  return 0;
+}
+
+bool syncRaftLogIsUptodate(SSyncRaftLog* pLog, SyncIndex index, SyncTerm term) {
+  return true;
+}
+
+int syncRaftLogNumOfPendingConf(SSyncRaftLog* pLog) {
+  return 0;
+}
+
+bool syncRaftHasUnappliedLog(SSyncRaftLog* pLog) {
+  return pLog->commitIndex > pLog->appliedIndex;
+}
+
+SyncTerm syncRaftLogTermOf(SSyncRaftLog* pLog, SyncIndex index) {
+  return SYNC_NON_TERM;
+}
+
+int syncRaftLogAppend(SSyncRaftLog* pLog, SSyncRaftEntry *pEntries, int n) {
+
+}
+
+int syncRaftLogAcquire(SSyncRaftLog* pLog, SyncIndex index, int maxMsgSize,
+                      SSyncRaftEntry **ppEntries, int *n) {
+  return 0;
+}
+
+void syncRaftLogRelease(SSyncRaftLog* pLog, SyncIndex index,
+                      SSyncRaftEntry *pEntries, int n) {
+  return;
+}
\ No newline at end of file

source/libs/sync/src/raft_message.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "raft_message.h"
+
+void syncFreeMessage(const SSyncMessage* pMsg) {
+  if (!syncIsInternalMsg(pMsg->msgType)) {
+    free((SSyncMessage*)pMsg);
+  }
+}
\ No newline at end of file

source/libs/sync/src/raft_replication.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "raft.h"
+#include "raft_log.h"
+#include "sync_raft_progress.h"
+#include "raft_replication.h"
+
+static int sendSnapshot(SSyncRaft* pRaft, int i);
+static int sendAppendEntries(SSyncRaft* pRaft, int i, SyncIndex index, SyncTerm term);
+
+int syncRaftReplicate(SSyncRaft* pRaft, int i) {
+#if 0
+  assert(pRaft->state == TAOS_SYNC_ROLE_LEADER);
+  assert(i >= 0 && i < pRaft->leaderState.nProgress);
+
+  SyncNodeId nodeId = pRaft->cluster.nodeInfo[i].nodeId;
+  SSyncRaftProgress* progress = &(pRaft->leaderState.progress[i]);
+  if (syncRaftProgressIsPaused(progress)) {
+    syncInfo("node %d paused", nodeId);
+    return 0;
+  }
+
+  SyncIndex nextIndex = syncRaftProgressNextIndex(progress);
+  SyncIndex snapshotIndex = syncRaftLogSnapshotIndex(pRaft->log);
+  bool inSnapshot = syncRaftProgressInSnapshot(progress);
+  SyncIndex prevIndex;
+  SyncTerm prevTerm;
+
+  /**
+   * From Section 3.5:
+   *
+   *   When sending an AppendEntries RPC, the leader includes the index and
+   *   term of the entry in its log that immediately precedes the new
+   *   entries. If the follower does not find an entry in its log with the
+   *   same index and term, then it refuses the new entries. The consistency
+   *   check acts as an induction step: the initial empty state of the logs
+   *   satisfies the Log Matching Property, and the consistency check
+   *   preserves the Log Matching Property whenever logs are extended. As a
+   *   result, whenever AppendEntries returns successfully, the leader knows
+   *   that the follower's log is identical to its own log up through the new
+   *   entries (Log Matching Property in Figure 3.2).
+   **/
+  if (nextIndex == 1) {
+    /**
+     * We're including the very first entry, so prevIndex and prevTerm are
+     * null. If the first entry is not available anymore, send the last
+     * snapshot if we're not already sending one. 
+     **/
+    if (snapshotIndex > 0 && !inSnapshot) {
+      goto send_snapshot;
+    }
+
+    // otherwise send append entries from start
+    prevIndex = 0;
+    prevTerm = 0;    
+  } else {
+    /**
+     * Set prevIndex and prevTerm to the index and term of the entry at
+     * nextIndex - 1. 
+     **/ 
+    prevIndex = nextIndex - 1;
+    prevTerm = syncRaftLogTermOf(pRaft->log, prevIndex);
+    /**
+     * If the entry is not anymore in our log, send the last snapshot if we're
+     * not doing so already.
+     **/
+    if (prevTerm == SYNC_NON_TERM && !inSnapshot) {
+      goto send_snapshot;
+    }
+  }
+
+  /* Send empty AppendEntries RPC when installing a snaphot */
+  if (inSnapshot) {
+    prevIndex = syncRaftLogLastIndex(pRaft->log);
+    prevTerm = syncRaftLogLastTerm(pRaft->log);
+  }
+
+  return sendAppendEntries(pRaft, i, prevIndex, prevTerm);
+
+send_snapshot:
+  if (syncRaftProgressRecentActive(progress)) {
+    /* Only send a snapshot when we have heard from the server */
+    return sendSnapshot(pRaft, i);
+  } else {
+    /* Send empty AppendEntries RPC when we haven't heard from the server */
+    prevIndex = syncRaftLogLastIndex(pRaft->log);
+    prevTerm  = syncRaftLogLastTerm(pRaft->log);
+    return sendAppendEntries(pRaft, i, prevIndex, prevTerm);
+  }
+#endif
+  return 0;
+}
+
+static int sendSnapshot(SSyncRaft* pRaft, int i) {
+  return 0;
+}
+
+static int sendAppendEntries(SSyncRaft* pRaft, int i, SyncIndex prevIndex, SyncTerm prevTerm) {
+#if 0
+  SyncIndex nextIndex = prevIndex + 1;
+  SSyncRaftEntry *entries;
+  int nEntry;
+  SNodeInfo* pNode = &(pRaft->cluster.nodeInfo[i]);
+  SSyncRaftProgress* progress = &(pRaft->leaderState.progress[i]);
+  syncRaftLogAcquire(pRaft->log, nextIndex, pRaft->maxMsgSize, &entries, &nEntry);
+
+  SSyncMessage* msg = syncNewAppendMsg(pRaft->selfGroupId, pRaft->selfId, pRaft->term,
+                                      prevIndex, prevTerm, pRaft->log->commitIndex,
+                                      nEntry, entries);
+
+  if (msg == NULL) {
+    goto err_release_log;
+  }
+
+  pRaft->io.send(msg, pNode);
+
+  if (syncRaftProgressInReplicate(progress)) {
+    SyncIndex lastIndex = nextIndex + nEntry;
+    syncRaftProgressOptimisticNextIndex(progress, lastIndex);
+    syncRaftInflightAdd(&progress->inflights, lastIndex);
+  } else if (syncRaftProgressInProbe(progress)) {
+    syncRaftProgressPause(progress);
+  } else {
+
+  }
+
+  syncRaftProgressUpdateSendTick(progress, pRaft->currentTick);
+
+  return 0;
+
+err_release_log:
+  syncRaftLogRelease(pRaft->log, nextIndex, entries, nEntry);
+#endif
+  return 0;
+}
\ No newline at end of file

source/libs/sync/inc/raftInt.h → source/libs/sync/src/raft_unstable_log.c

 /*
- * Copyright (c) 2019 TAOS Data, Inc. <jhtao@taosdata.com>
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
  *
  * This program is free software: you can use, redistribute, and/or modify
  * it under the terms of the GNU Affero General Public License, version 3
@@ -13,15 +13,11 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef _TD_RAFT_INT_H_
-#define _TD_RAFT_INT_H_
+#include "sync.h"
+#include "raft_unstable_log.h"
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-#ifdef __cplusplus
+/*
+SyncIndex syncRaftLogLastIndex(SSyncRaftUnstableLog* pLog) {
+  return 0;
 }
-#endif
-
+*/
\ No newline at end of file
-#endif /*_TD_RAFT_INT_H_*/
\ No newline at end of file

source/libs/sync/src/sync.c

@@ -13,14 +13,282 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "sync.h"
+#include "syncInt.h"
+#include "trpc.h"
+#include "ttimer.h"
 
-int32_t syncInit() { return 0; }
+SSyncManager* gSyncManager = NULL;
 
-void syncCleanUp() {}
+#define SYNC_TICK_TIMER 50
+#define SYNC_ACTIVITY_TIMER 5
+#define SYNC_SERVER_WORKER 2
 
-SSyncNode* syncStart(const SSyncInfo* pInfo) { return NULL; }
+static void syncProcessRsp(SRpcMsg *pMsg, SEpSet *pEpSet);
+static void syncProcessReqMsg(SRpcMsg *pMsg, SEpSet *pEpSet);
 
-void syncStop(const SSyncNode* pNode) {}
+static int syncInitRpcServer(SSyncManager* syncManager, const SSyncCluster* pSyncCfg);
+static int syncInitRpcClient(SSyncManager* syncManager);
+static int syncOpenWorkerPool(SSyncManager* syncManager);
+static int syncCloseWorkerPool(SSyncManager* syncManager);
+static void *syncWorkerMain(void *argv);
+static void syncNodeTick(void *param, void *tmrId);
+
+int32_t syncInit() { 
+  if (gSyncManager != NULL) {
+    return 0;
+  }
+
+  gSyncManager = (SSyncManager*)calloc(sizeof(SSyncManager), 0);
+  if (gSyncManager == NULL) {
+    syncError("malloc SSyncManager fail");
+    return -1;
+  }
+
+  pthread_mutex_init(&gSyncManager->mutex, NULL);
+
+  // init client rpc
+  if (syncInitRpcClient(gSyncManager) != 0) {
+    syncCleanUp();
+    return -1;
+  }
+
+  // init sync timer manager
+  gSyncManager->syncTimerManager = taosTmrInit(1000, 50, 10000, "SYNC");
+  if (gSyncManager->syncTimerManager == NULL) {
+    syncCleanUp();
+    return -1;
+  }
+
+  // init worker pool
+  if (syncOpenWorkerPool(gSyncManager) != 0) {
+    syncCleanUp();
+    return -1;
+  }
+
+  // init vgroup hash table
+  gSyncManager->vgroupTable = taosHashInit(TSDB_MIN_VNODES, taosGetDefaultHashFunction(TSDB_DATA_TYPE_INT), true, HASH_ENTRY_LOCK);
+  if (gSyncManager->vgroupTable == NULL) {
+    syncCleanUp();
+    return -1;
+  }
+  return 0; 
+}
+
+void syncCleanUp() {
+  if (gSyncManager == NULL) {
+    return;
+  }
+  pthread_mutex_lock(&gSyncManager->mutex);
+  if (gSyncManager->vgroupTable) {
+    taosHashCleanup(gSyncManager->vgroupTable);
+  }
+  if (gSyncManager->clientRpc) {
+    rpcClose(gSyncManager->clientRpc);
+    syncInfo("sync inter-sync rpc client is closed");
+  }
+  if (gSyncManager->syncTimerManager) {
+    taosTmrCleanUp(gSyncManager->syncTimerManager);
+  }
+  syncCloseWorkerPool(gSyncManager);
+  pthread_mutex_unlock(&gSyncManager->mutex);
+  pthread_mutex_destroy(&gSyncManager->mutex);
+  free(gSyncManager);
+  gSyncManager = NULL;
+}
+
+SSyncNode* syncStart(const SSyncInfo* pInfo) {
+  pthread_mutex_lock(&gSyncManager->mutex);
+
+  SSyncNode **ppNode = taosHashGet(gSyncManager->vgroupTable, &pInfo->vgId, sizeof(SyncGroupId));
+  if (ppNode != NULL) {
+    syncInfo("vgroup %d already exist", pInfo->vgId);
+    pthread_mutex_unlock(&gSyncManager->mutex);
+    return *ppNode;
+  }
+
+  // init rpc server
+  if (syncInitRpcServer(gSyncManager, &pInfo->syncCfg) != 0) {
+    pthread_mutex_unlock(&gSyncManager->mutex);
+    return NULL;
+  }
+
+  SSyncNode *pNode = (SSyncNode*)malloc(sizeof(SSyncNode));
+  if (pNode == NULL) {
+    syncError("malloc vgroup %d node fail", pInfo->vgId);
+    pthread_mutex_unlock(&gSyncManager->mutex);
+    return NULL;
+  }
+
+  pNode->syncTimer = taosTmrStart(syncNodeTick, SYNC_TICK_TIMER, (void*)pInfo->vgId, gSyncManager->syncTimerManager);
+
+  // start raft
+  pNode->raft.pNode = pNode;
+  if (syncRaftStart(&pNode->raft, pInfo) != 0) {
+    syncError("raft start at %d node fail", pInfo->vgId);
+    pthread_mutex_unlock(&gSyncManager->mutex);
+    return NULL;
+  }
+
+  pthread_mutex_init(&pNode->mutex, NULL);
+
+  taosHashPut(gSyncManager->vgroupTable, &pInfo->vgId, sizeof(SyncGroupId), &pNode, sizeof(SSyncNode *));
+
+  pthread_mutex_unlock(&gSyncManager->mutex);
+  return NULL;
+}
+
+void syncStop(const SSyncNode* pNode) {
+  pthread_mutex_lock(&gSyncManager->mutex);
+
+  SSyncNode **ppNode = taosHashGet(gSyncManager->vgroupTable, &pNode->vgId, sizeof(SyncGroupId));
+  if (ppNode == NULL) {
+    syncInfo("vgroup %d not exist", pNode->vgId);
+    pthread_mutex_unlock(&gSyncManager->mutex);
+    return;
+  }
+  assert(*ppNode == pNode);
+  taosTmrStop(pNode->syncTimer);
+
+  taosHashRemove(gSyncManager->vgroupTable, &pNode->vgId, sizeof(SyncGroupId));
+  pthread_mutex_unlock(&gSyncManager->mutex);
+
+  pthread_mutex_destroy(&((*ppNode)->mutex));
+  free(*ppNode);
+}
+
+int32_t syncPropose(SSyncNode* syncNode, const SSyncBuffer* pBuf, void* pData, bool isWeak) {
+  SSyncMessage msg;
+
+  pthread_mutex_lock(&syncNode->mutex);
+  int32_t ret = syncRaftStep(&syncNode->raft, syncInitPropMsg(&msg, pBuf, pData, isWeak));
+  pthread_mutex_unlock(&syncNode->mutex);
+  return ret;
+}
 
 void syncReconfig(const SSyncNode* pNode, const SSyncCluster* pCfg) {}
+
+// process rpc rsp message from other sync server
+static void syncProcessRsp(SRpcMsg *pMsg, SEpSet *pEpSet) {
+
+}
+
+// process rpc message from other sync server
+static void syncProcessReqMsg(SRpcMsg *pMsg, SEpSet *pEpSet) {
+
+}
+
+static int syncInitRpcServer(SSyncManager* syncManager, const SSyncCluster* pSyncCfg) {
+  if (gSyncManager->rpcServerTable == NULL) {
+    gSyncManager->rpcServerTable = taosHashInit(TSDB_MIN_VNODES, taosGetDefaultHashFunction(TSDB_DATA_TYPE_BINARY), true, HASH_ENTRY_LOCK);
+    if (gSyncManager->rpcServerTable == NULL) {
+      syncError("init sync rpc server hash table error");
+      return -1;
+    }
+  }
+  assert(pSyncCfg->selfIndex < pSyncCfg->replica && pSyncCfg->selfIndex >= 0);
+  const SNodeInfo* pNode = &(pSyncCfg->nodeInfo[pSyncCfg->replica]);
+  char buffer[20] = {'\0'};
+  snprintf(buffer, sizeof(buffer), "%s:%d", &(pNode->nodeFqdn[0]), pNode->nodePort);
+  size_t len = strlen(buffer);
+  void** ppRpcServer = taosHashGet(gSyncManager->rpcServerTable, buffer, len);
+  if (ppRpcServer != NULL) {
+    // already inited
+    syncInfo("sync rpc server for %s already exist", buffer);
+    return 0;
+  }
+
+  SRpcInit rpcInit;
+  memset(&rpcInit, 0, sizeof(rpcInit));
+  rpcInit.localPort    = pNode->nodePort;
+  rpcInit.label        = "sync-server";
+  rpcInit.numOfThreads = SYNC_SERVER_WORKER;
+  rpcInit.cfp          = syncProcessReqMsg;
+  rpcInit.sessions     = TSDB_MAX_VNODES << 4;
+  rpcInit.connType     = TAOS_CONN_SERVER;
+  rpcInit.idleTime     = SYNC_ACTIVITY_TIMER * 1000;
+
+  void* rpcServer = rpcOpen(&rpcInit);
+  if (rpcServer == NULL) {
+    syncInfo("rpcOpen for sync rpc server for %s fail", buffer);
+    return -1;
+  }
+
+  taosHashPut(gSyncManager->rpcServerTable, buffer, strlen(buffer), rpcServer, len);
+  syncInfo("sync rpc server for %s init success", buffer);
+
+  return 0;
+}
+
+static int syncInitRpcClient(SSyncManager* syncManager) {
+  char secret[TSDB_KEY_LEN] = "secret";
+  SRpcInit rpcInit;
+  memset(&rpcInit, 0, sizeof(rpcInit));
+  rpcInit.label        = "sync-client";
+  rpcInit.numOfThreads = 1;
+  rpcInit.cfp          = syncProcessRsp;
+  rpcInit.sessions     = TSDB_MAX_VNODES << 4;
+  rpcInit.connType     = TAOS_CONN_CLIENT;
+  rpcInit.idleTime     = SYNC_ACTIVITY_TIMER * 1000;
+  rpcInit.user         = "t";
+  rpcInit.ckey         = "key";
+  rpcInit.secret       = secret;
+
+  syncManager->clientRpc = rpcOpen(&rpcInit);
+  if (syncManager->clientRpc == NULL) {
+    syncError("failed to init sync rpc client");
+    return -1;
+  }
+
+  syncInfo("sync inter-sync rpc client is initialized");
+  return 0;
+}
+
+static int syncOpenWorkerPool(SSyncManager* syncManager) {
+  int i;
+  pthread_attr_t thattr;
+
+  pthread_attr_init(&thattr);
+  pthread_attr_setdetachstate(&thattr, PTHREAD_CREATE_JOINABLE); 
+
+  for (i = 0; i < TAOS_SYNC_MAX_WORKER; ++i) {
+    SSyncWorker* pWorker = &(syncManager->worker[i]);
+
+    if (pthread_create(&(pWorker->thread), &thattr, (void *)syncWorkerMain, pWorker) != 0) {
+      syncError("failed to create sync worker since %s", strerror(errno));
+
+      return -1;
+    }
+  }
+
+  pthread_attr_destroy(&thattr);
+
+  return 0;
+}
+
+static int syncCloseWorkerPool(SSyncManager* syncManager) {
+  return 0;
+}
+
+static void *syncWorkerMain(void *argv) {
+  SSyncWorker* pWorker = (SSyncWorker *)argv;
+
+  taosBlockSIGPIPE();
+  setThreadName("syncWorker");
+
+  return NULL;
+}
+
+static void syncNodeTick(void *param, void *tmrId) {
+  SyncGroupId vgId = (SyncGroupId)param;
+  SSyncNode **ppNode = taosHashGet(gSyncManager->vgroupTable, &vgId, sizeof(SyncGroupId));
+  if (ppNode == NULL) {
+    return;
+  }
+  SSyncNode *pNode = *ppNode;
+
+  pthread_mutex_lock(&pNode->mutex);
+  syncRaftTick(&pNode->raft);
+  pthread_mutex_unlock(&pNode->mutex);
+
+  pNode->syncTimer = taosTmrStart(syncNodeTick, SYNC_TICK_TIMER, (void*)pNode->vgId, gSyncManager->syncTimerManager);
+}
\ No newline at end of file

source/libs/sync/src/sync_raft_impl.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "raft.h"
+#include "raft_configuration.h"
+#include "raft_log.h"
+#include "raft_replication.h"
+#include "sync_raft_progress_tracker.h"
+#include "syncInt.h"
+
+static int convertClear(SSyncRaft* pRaft);
+static int stepFollower(SSyncRaft* pRaft, const SSyncMessage* pMsg);
+static int stepCandidate(SSyncRaft* pRaft, const SSyncMessage* pMsg);
+static int stepLeader(SSyncRaft* pRaft, const SSyncMessage* pMsg);
+
+static int triggerAll(SSyncRaft* pRaft);
+
+static void tickElection(SSyncRaft* pRaft);
+static void tickHeartbeat(SSyncRaft* pRaft);
+
+static void appendEntries(SSyncRaft* pRaft, SSyncRaftEntry* entries, int n);
+static bool maybeCommit(SSyncRaft* pRaft);
+
+static void abortLeaderTransfer(SSyncRaft* pRaft);
+
+static void resetRaft(SSyncRaft* pRaft, SyncTerm term);
+
+void syncRaftBecomeFollower(SSyncRaft* pRaft, SyncTerm term, SyncNodeId leaderId) {
+  convertClear(pRaft);
+
+  pRaft->stepFp = stepFollower;
+  resetRaft(pRaft, term);
+  pRaft->tickFp = tickElection;
+  pRaft->leaderId = leaderId;
+  pRaft->state = TAOS_SYNC_ROLE_FOLLOWER;
+  syncInfo("[%d:%d] became followe at term %" PRId64 "", pRaft->selfGroupId, pRaft->selfId, pRaft->term);
+}
+
+void syncRaftBecomePreCandidate(SSyncRaft* pRaft) {
+  convertClear(pRaft);
+
+	/**
+   * Becoming a pre-candidate changes our step functions and state,
+	 * but doesn't change anything else. In particular it does not increase
+	 * r.Term or change r.Vote.
+   **/
+  pRaft->stepFp = stepCandidate;
+  pRaft->tickFp = tickElection;
+  pRaft->state  = TAOS_SYNC_ROLE_CANDIDATE;
+  pRaft->candidateState.inPreVote = true;
+  syncInfo("[%d:%d] became pre-candidate at term %" PRId64 "", pRaft->selfGroupId, pRaft->selfId, pRaft->term);
+}
+
+void syncRaftBecomeCandidate(SSyncRaft* pRaft) {
+  convertClear(pRaft);
+
+  pRaft->candidateState.inPreVote = false;
+  pRaft->stepFp = stepCandidate;
+  // become candidate make term+1
+  resetRaft(pRaft, pRaft->term + 1);
+  pRaft->tickFp = tickElection;
+  pRaft->voteFor = pRaft->selfId;
+  pRaft->state  = TAOS_SYNC_ROLE_CANDIDATE;
+  syncInfo("[%d:%d] became candidate at term %" PRId64 "", pRaft->selfGroupId, pRaft->selfId, pRaft->term);
+}
+
+void syncRaftBecomeLeader(SSyncRaft* pRaft) {
+  assert(pRaft->state != TAOS_SYNC_ROLE_FOLLOWER);
+
+  pRaft->stepFp = stepLeader;
+  resetRaft(pRaft, pRaft->term);
+  pRaft->leaderId = pRaft->leaderId;
+  pRaft->state  = TAOS_SYNC_ROLE_LEADER;
+  // TODO: check if there is pending config log
+  int nPendingConf = syncRaftLogNumOfPendingConf(pRaft->log);
+  if (nPendingConf > 1) {
+    syncFatal("unexpected multiple uncommitted config entry");
+  }
+
+  syncInfo("[%d:%d] became leader at term %" PRId64 "", pRaft->selfGroupId, pRaft->selfId, pRaft->term);
+
+  // after become leader, send a no-op log
+  SSyncRaftEntry* entry = (SSyncRaftEntry*)malloc(sizeof(SSyncRaftEntry));
+  if (entry == NULL) {
+    return;
+  }
+  *entry = (SSyncRaftEntry) {
+    .buffer = (SSyncBuffer) {
+      .data = NULL,
+      .len = 0,
+    }
+  };
+  appendEntries(pRaft, entry, 1);
+  //syncRaftTriggerHeartbeat(pRaft);
+}
+
+void syncRaftTriggerHeartbeat(SSyncRaft* pRaft) {
+  triggerAll(pRaft);
+}
+
+void syncRaftRandomizedElectionTimeout(SSyncRaft* pRaft) {
+  // electionTimeoutTick in [3,6] tick
+  pRaft->randomizedElectionTimeout = taosRand() % 4 + 3;
+}
+
+bool syncRaftIsPromotable(SSyncRaft* pRaft) {
+  return pRaft->selfId != SYNC_NON_NODE_ID;
+}
+
+bool syncRaftIsPastElectionTimeout(SSyncRaft* pRaft) {
+  return pRaft->electionElapsed >= pRaft->randomizedElectionTimeout;
+}
+
+int syncRaftQuorum(SSyncRaft* pRaft) {
+  return pRaft->cluster.replica / 2 + 1;
+}
+
+SSyncRaftVoteResult  syncRaftPollVote(SSyncRaft* pRaft, SyncNodeId id, 
+                                      bool preVote, bool grant, 
+                                      int* rejected, int *granted) {
+  int voterIndex = syncRaftConfigurationIndexOfNode(pRaft, id);
+  if (voterIndex == -1) {
+    return SYNC_RAFT_VOTE_PENDING;
+  }
+
+  if (grant) {
+    syncInfo("[%d:%d] received grant (pre-vote %d) from %d at term %" PRId64 "", 
+      pRaft->selfGroupId, pRaft->selfId, preVote, id, pRaft->term);
+  } else {
+    syncInfo("[%d:%d] received rejection (pre-vote %d) from %d at term %" PRId64 "", 
+      pRaft->selfGroupId, pRaft->selfId, preVote, id, pRaft->term);
+  }
+
+  syncRaftRecordVote(pRaft->tracker, voterIndex, grant);
+  return syncRaftTallyVotes(pRaft->tracker, rejected, granted);
+}
+/*
+  if (accept) {
+    syncInfo("[%d:%d] received (pre-vote %d) from %d at term %" PRId64 "", 
+      pRaft->selfGroupId, pRaft->selfId, preVote, id, pRaft->term);
+  } else {
+    syncInfo("[%d:%d] received rejection from %d at term %" PRId64 "", 
+      pRaft->selfGroupId, pRaft->selfId, id, pRaft->term);
+  }
+  
+  int voteIndex = syncRaftConfigurationIndexOfNode(pRaft, id);
+  assert(voteIndex < pRaft->cluster.replica && voteIndex >= 0);
+  assert(pRaft->candidateState.votes[voteIndex] == SYNC_RAFT_VOTE_RESP_UNKNOWN);
+
+  pRaft->candidateState.votes[voteIndex] = accept ? SYNC_RAFT_VOTE_RESP_GRANT : SYNC_RAFT_VOTE_RESP_REJECT;
+  int granted = 0, rejected = 0;
+  int i;
+  for (i = 0; i < pRaft->cluster.replica; ++i) {
+    if (pRaft->candidateState.votes[i] == SYNC_RAFT_VOTE_RESP_GRANT) granted++;
+    else if (pRaft->candidateState.votes[i] == SYNC_RAFT_VOTE_RESP_REJECT) rejected++;
+  }
+
+  if (rejectNum) *rejectNum = rejected;
+  return granted;
+*/
+
+static int convertClear(SSyncRaft* pRaft) {
+
+}
+
+static int stepFollower(SSyncRaft* pRaft, const SSyncMessage* pMsg) {
+  
+  return 0;
+}
+
+static int stepCandidate(SSyncRaft* pRaft, const SSyncMessage* pMsg) {
+  /**
+   * Only handle vote responses corresponding to our candidacy (while in
+	 * StateCandidate, we may get stale MsgPreVoteResp messages in this term from
+	 * our pre-candidate state).
+   **/
+  RaftMessageType msgType = pMsg->msgType;
+
+  if (msgType == RAFT_MSG_INTERNAL_PROP) {
+    return 0;
+  }
+
+  if (msgType == RAFT_MSG_VOTE_RESP) {
+    syncRaftHandleVoteRespMessage(pRaft, pMsg);
+    return 0;
+  } else if (msgType == RAFT_MSG_APPEND) {
+    syncRaftBecomeFollower(pRaft, pRaft->term, pMsg->from);
+    syncRaftHandleAppendEntriesMessage(pRaft, pMsg);
+  }
+  return 0;
+}
+
+static int stepLeader(SSyncRaft* pRaft, const SSyncMessage* pMsg) {
+  convertClear(pRaft);
+  return 0;
+}
+
+/**
+ *  tickElection is run by followers and candidates per tick.
+ **/
+static void tickElection(SSyncRaft* pRaft) {
+  pRaft->electionElapsed += 1;
+
+  if (!syncRaftIsPromotable(pRaft)) {
+    return;
+  }
+
+  if (!syncRaftIsPastElectionTimeout(pRaft)) {
+    return;
+  }
+
+  // election timeout
+  pRaft->electionElapsed = 0;
+  SSyncMessage msg;
+  syncRaftStep(pRaft, syncInitElectionMsg(&msg, pRaft->selfId));
+}
+
+static void tickHeartbeat(SSyncRaft* pRaft) {
+
+}
+
+static void appendEntries(SSyncRaft* pRaft, SSyncRaftEntry* entries, int n) {
+  SyncIndex lastIndex = syncRaftLogLastIndex(pRaft->log);
+  SyncTerm term = pRaft->term;
+  int i;
+
+  for (i = 0; i < n; ++i) {
+    entries[i].term = term;
+    entries[i].index = lastIndex + 1 + i;
+  }
+
+  syncRaftLogAppend(pRaft->log, entries, n);
+
+  SSyncRaftProgress* progress = &(pRaft->tracker->progressMap[pRaft->cluster.selfIndex]);
+  syncRaftProgressMaybeUpdate(progress, lastIndex);
+  // Regardless of maybeCommit's return, our caller will call bcastAppend.
+  maybeCommit(pRaft);
+}
+
+/**
+ * maybeCommit attempts to advance the commit index. Returns true if
+ * the commit index changed (in which case the caller should call
+ * r.bcastAppend).
+ **/
+static bool maybeCommit(SSyncRaft* pRaft) {
+  
+  return true;
+}
+
+/**
+ * trigger I/O requests for newly appended log entries or heartbeats.
+ **/
+static int triggerAll(SSyncRaft* pRaft) {
+  assert(pRaft->state == TAOS_SYNC_ROLE_LEADER);
+  int i;
+
+  for (i = 0; i < pRaft->cluster.replica; ++i) {
+    if (i == pRaft->cluster.selfIndex) {
+      continue;
+    }
+
+    syncRaftReplicate(pRaft, i);
+  }
+}
+
+static void abortLeaderTransfer(SSyncRaft* pRaft) {
+  pRaft->leadTransferee = SYNC_NON_NODE_ID;
+}
+
+static void initProgress(int i, SSyncRaftProgress* progress, void* arg) {
+  syncRaftInitProgress(i, (SSyncRaft*)arg, progress);
+}
+
+static void resetRaft(SSyncRaft* pRaft, SyncTerm term) {
+  if (pRaft->term != term) {
+    pRaft->term = term;
+    pRaft->voteFor = SYNC_NON_NODE_ID;
+  }
+
+  pRaft->leaderId = SYNC_NON_NODE_ID;
+
+  pRaft->electionElapsed = 0;
+  pRaft->heartbeatElapsed = 0;
+
+  syncRaftRandomizedElectionTimeout(pRaft);
+
+  abortLeaderTransfer(pRaft);
+
+  syncRaftResetVotes(pRaft->tracker);
+  syncRaftProgressVisit(pRaft->tracker, initProgress, pRaft);
+
+  pRaft->pendingConfigIndex = 0;
+  pRaft->uncommittedSize = 0;
+}
\ No newline at end of file

source/libs/sync/src/sync_raft_inflights.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http: *www.gnu.org/licenses/>.
+ */
+
+#include "sync_raft_inflights.h"
+
+SSyncRaftInflights* syncRaftOpenInflights(int size) {
+  SSyncRaftInflights* inflights = (SSyncRaftInflights*)malloc(sizeof(SSyncRaftInflights));
+  if (inflights == NULL) {
+    return NULL;
+  }
+  SyncIndex* buffer = (SyncIndex*)malloc(sizeof(SyncIndex) * size);
+  if (buffer == NULL) {
+    free(inflights);
+    return NULL;
+  }
+  *inflights = (SSyncRaftInflights) {
+    .buffer = buffer,
+    .count  = 0,
+    .size   = 0,
+    .start  = 0,
+  };
+
+  return inflights;
+}
+
+void syncRaftCloseInflights(SSyncRaftInflights* inflights) {
+  free(inflights->buffer);
+  free(inflights);
+}
+
+/**
+ * syncRaftInflightAdd notifies the Inflights that a new message with the given index is being
+ * dispatched. syncRaftInflightFull() must be called prior to syncRaftInflightAdd() 
+ * to verify that there is room for one more message, 
+ * and consecutive calls to add syncRaftInflightAdd() must provide a
+ * monotonic sequence of indexes.
+ **/
+void syncRaftInflightAdd(SSyncRaftInflights* inflights, SyncIndex inflightIndex) {
+  assert(!syncRaftInflightFull(inflights));
+
+  int next = inflights->start + inflights->count;
+  int size = inflights->size;
+  /* is next wrapped around buffer? */
+  if (next >= size) {
+    next -= size;
+  }
+
+  inflights->buffer[next] = inflightIndex;
+  inflights->count++;
+}
+
+/**
+ * syncRaftInflightFreeLE frees the inflights smaller or equal to the given `to` flight.
+ **/
+void syncRaftInflightFreeLE(SSyncRaftInflights* inflights, SyncIndex toIndex) {
+  if (inflights->count == 0 || toIndex < inflights->buffer[inflights->start]) {
+    /* out of the left side of the window */
+    return;
+  }
+
+  int i, idx;
+  for (i = 0, idx = inflights->start; i < inflights->count; i++) {
+    if (toIndex < inflights->buffer[idx]) { // found the first large inflight
+      break;
+    }
+
+    // increase index and maybe rotate
+    int size = inflights->size;
+    idx++;
+    if (idx >= size) {
+      idx -= size;
+    }
+  }
+
+  // free i inflights and set new start index
+  inflights->count -= i;
+  inflights->start  = idx;
+  assert(inflights->count >= 0);
+  if (inflights->count == 0) {
+		// inflights is empty, reset the start index so that we don't grow the
+		// buffer unnecessarily.    
+    inflights->start = 0;
+  }
+}
+
+/** 
+ * syncRaftInflightFreeFirstOne releases the first inflight. 
+ * This is a no-op if nothing is inflight.
+ **/
+void syncRaftInflightFreeFirstOne(SSyncRaftInflights* inflights) {
+  syncRaftInflightFreeLE(inflights, inflights->buffer[inflights->start]);
+}

source/libs/sync/src/sync_raft_progress.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "raft.h"
+#include "raft_log.h"
+#include "sync_raft_progress.h"
+#include "sync_raft_progress_tracker.h"
+#include "sync.h"
+#include "syncInt.h"
+
+static void resetProgressState(SSyncRaftProgress* progress, RaftProgressState state);
+static void probeAcked(SSyncRaftProgress* progress);
+
+static void resumeProgress(SSyncRaftProgress* progress);
+
+void syncRaftInitProgress(int i, SSyncRaft* pRaft, SSyncRaftProgress* progress) {
+  SSyncRaftInflights* inflights = syncRaftOpenInflights(pRaft->tracker->maxInflight);
+  if (inflights == NULL) {
+    return;
+  }
+  *progress = (SSyncRaftProgress) {
+    .matchIndex = i == pRaft->selfIndex ? syncRaftLogLastIndex(pRaft->log) : 0,
+    .nextIndex  = syncRaftLogLastIndex(pRaft->log) + 1,
+    .inflights  = inflights,
+    .isLearner  = false,
+    .state      = PROGRESS_STATE_PROBE,
+  };
+}
+
+/**
+ * syncRaftProgressMaybeUpdate is called when an MsgAppResp arrives from the follower, with the
+ * index acked by it. The method returns false if the given n index comes from
+ * an outdated message. Otherwise it updates the progress and returns true.
+ **/
+bool syncRaftProgressMaybeUpdate(SSyncRaftProgress* progress, SyncIndex lastIndex) {
+  bool updated = false;
+
+  if (progress->matchIndex < lastIndex) {
+    progress->matchIndex = lastIndex;
+    updated = true;
+    probeAcked(progress);
+  }
+
+  progress->nextIndex = MAX(progress->nextIndex, lastIndex + 1);
+
+  return updated;
+}
+
+bool syncRaftProgressMaybeDecrTo(SSyncRaftProgress* progress,
+                                SyncIndex rejected, SyncIndex matchHint) {
+  if (progress->state == PROGRESS_STATE_REPLICATE) {
+		/** 
+     * the rejection must be stale if the progress has matched and "rejected"
+		 * is smaller than "match".
+     **/
+    if (rejected <= progress->matchIndex) {
+      syncDebug("match index is up to date,ignore");
+      return false;
+    }
+
+    /* directly decrease next to match + 1 */
+    progress->nextIndex = progress->matchIndex + 1;
+    return true;
+  }
+
+	/**
+   * The rejection must be stale if "rejected" does not match next - 1. This
+	 * is because non-replicating followers are probed one entry at a time.
+   **/
+  if (rejected != progress->nextIndex - 1) {
+    syncDebug("rejected index %" PRId64 " different from next index %" PRId64 " -> ignore"
+      , rejected, progress->nextIndex);
+    return false;
+  }
+
+  progress->nextIndex = MAX(MIN(rejected, matchHint + 1), 1);
+
+  progress->probeSent = false;
+  return true;
+}
+
+/**
+ * syncRaftProgressIsPaused returns whether sending log entries to this node has been throttled.
+ * This is done when a node has rejected recent MsgApps, is currently waiting
+ * for a snapshot, or has reached the MaxInflightMsgs limit. In normal
+ * operation, this is false. A throttled node will be contacted less frequently
+ * until it has reached a state in which it's able to accept a steady stream of
+ * log entries again.
+ **/
+bool syncRaftProgressIsPaused(SSyncRaftProgress* progress) {
+  switch (progress->state) {
+    case PROGRESS_STATE_PROBE:
+      return progress->probeSent;
+    case PROGRESS_STATE_REPLICATE:
+      return syncRaftInflightFull(progress->inflights);
+    case PROGRESS_STATE_SNAPSHOT:
+      return true;
+    default:
+      syncFatal("error sync state:%d", progress->state);
+  }
+}
+
+bool syncRaftProgressIsUptodate(SSyncRaft* pRaft, SSyncRaftProgress* progress) {
+  return syncRaftLogLastIndex(pRaft->log) + 1 == progress->nextIndex;
+}
+
+/**
+ * syncRaftProgressBecomeProbe transitions into StateProbe. Next is reset to Match+1 or,
+ * optionally and if larger, the index of the pending snapshot.
+ **/
+void syncRaftProgressBecomeProbe(SSyncRaftProgress* progress) {
+  /**
+   * If the original state is ProgressStateSnapshot, progress knows that
+	 * the pending snapshot has been sent to this peer successfully, then
+	 * probes from pendingSnapshot + 1.
+   **/
+  if (progress->state == PROGRESS_STATE_SNAPSHOT) {
+    SyncIndex pendingSnapshotIndex = progress->pendingSnapshotIndex;
+    resetProgressState(progress, PROGRESS_STATE_PROBE);
+    progress->nextIndex = MAX(progress->matchIndex + 1, pendingSnapshotIndex + 1);
+  } else {
+    resetProgressState(progress, PROGRESS_STATE_PROBE);
+    progress->nextIndex = progress->matchIndex + 1;
+  }
+}
+
+/**
+ * syncRaftProgressBecomeReplicate transitions into StateReplicate, resetting Next to Match+1.
+ **/
+void syncRaftProgressBecomeReplicate(SSyncRaftProgress* progress) {
+  resetProgressState(progress, PROGRESS_STATE_REPLICATE);
+  progress->nextIndex = progress->matchIndex + 1;
+}
+
+void syncRaftProgressBecomeSnapshot(SSyncRaftProgress* progress, SyncIndex snapshotIndex) {
+  resetProgressState(progress, PROGRESS_STATE_SNAPSHOT);
+  progress->pendingSnapshotIndex = snapshotIndex;
+}
+
+/**
+ * ResetState moves the Progress into the specified State, resetting ProbeSent,
+ * PendingSnapshot, and Inflights.
+ **/
+static void resetProgressState(SSyncRaftProgress* progress, RaftProgressState state) {
+  progress->probeSent = false;
+  progress->pendingSnapshotIndex = 0;
+  progress->state = state;
+  syncRaftInflightReset(progress->inflights);
+}
+
+/**
+ * probeAcked is called when this peer has accepted an append. It resets
+ * ProbeSent to signal that additional append messages should be sent without
+ * further delay.
+ **/
+static void probeAcked(SSyncRaftProgress* progress) {
+  progress->probeSent = false;
+}
+
+#if 0
+
+SyncIndex syncRaftProgressNextIndex(SSyncRaft* pRaft, int i) {
+  return pRaft->leaderState.progress[i].nextIndex;
+}
+
+SyncIndex syncRaftProgressMatchIndex(SSyncRaft* pRaft, int i) {
+  return pRaft->leaderState.progress[i].matchIndex;
+}
+
+void syncRaftProgressUpdateLastSend(SSyncRaft* pRaft, int i) {
+  pRaft->leaderState.progress[i].lastSend = pRaft->io.time(pRaft);
+}
+
+void syncRaftProgressUpdateSnapshotLastSend(SSyncRaft* pRaft, int i) {
+  pRaft->leaderState.progress[i].lastSendSnapshot = pRaft->io.time(pRaft);
+}
+
+bool syncRaftProgressResetRecentRecv(SSyncRaft* pRaft, int i) {
+  SSyncRaftProgress* progress = &(pRaft->leaderState.progress[i]);
+  bool prev = progress->recentRecv;
+  progress->recentRecv = false;
+  return prev;
+}
+
+void syncRaftProgressMarkRecentRecv(SSyncRaft* pRaft, int i) {
+  pRaft->leaderState.progress[i].recentRecv = true;
+}
+
+bool syncRaftProgressGetRecentRecv(SSyncRaft* pRaft, int i) {
+  return pRaft->leaderState.progress[i].recentRecv;
+}
+
+void syncRaftProgressBecomeSnapshot(SSyncRaft* pRaft, int i) {
+  SSyncRaftProgress* progress = &(pRaft->leaderState.progress[i]);
+  resetProgressState(progress, PROGRESS_STATE_SNAPSHOT);
+  progress->pendingSnapshotIndex = raftLogSnapshotIndex(pRaft->log);
+}
+
+void syncRaftProgressBecomeProbe(SSyncRaft* pRaft, int i) {
+  SSyncRaftProgress* progress = &(pRaft->leaderState.progress[i]);
+
+  if (progress->state == PROGRESS_STATE_SNAPSHOT) {
+    assert(progress->pendingSnapshotIndex > 0);
+    SyncIndex pendingSnapshotIndex = progress->pendingSnapshotIndex;
+    resetProgressState(progress, PROGRESS_STATE_PROBE);
+    progress->nextIndex = max(progress->matchIndex + 1, pendingSnapshotIndex);
+  } else {
+    resetProgressState(progress, PROGRESS_STATE_PROBE);
+    progress->nextIndex = progress->matchIndex + 1;
+  }
+}
+
+void syncRaftProgressBecomeReplicate(SSyncRaft* pRaft, int i) {
+  resetProgressState(pRaft->leaderState.progress, PROGRESS_STATE_REPLICATE);
+  pRaft->leaderState.progress->nextIndex = pRaft->leaderState.progress->matchIndex + 1;
+}
+
+void syncRaftProgressAbortSnapshot(SSyncRaft* pRaft, int i) {
+  SSyncRaftProgress* progress = &(pRaft->leaderState.progress[i]);
+  progress->pendingSnapshotIndex = 0;
+  progress->state = PROGRESS_STATE_PROBE;
+}
+
+RaftProgressState syncRaftProgressState(SSyncRaft* pRaft, int i) {
+  return pRaft->leaderState.progress[i].state;
+}
+
+
+
+#endif
\ No newline at end of file

source/libs/sync/src/sync_raft_progress_tracker.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "sync_raft_progress_tracker.h"
+
+SSyncRaftProgressTracker* syncRaftOpenProgressTracker() {
+  SSyncRaftProgressTracker* tracker = (SSyncRaftProgressTracker*)malloc(sizeof(SSyncRaftProgressTracker));
+  if (tracker == NULL) {
+    return NULL;
+  }
+
+  return tracker;
+}
+
+void syncRaftResetVotes(SSyncRaftProgressTracker* tracker) {
+  memset(tracker->votes, SYNC_RAFT_VOTE_RESP_UNKNOWN, sizeof(SyncRaftVoteResult) * TSDB_MAX_REPLICA);
+}
+
+void syncRaftProgressVisit(SSyncRaftProgressTracker* tracker, visitProgressFp visit, void* arg) {
+  int i;
+  for (i = 0; i < TSDB_MAX_REPLICA; ++i) {
+    SSyncRaftProgress* progress = &(tracker->progressMap[i]);
+    visit(i, progress, arg);
+  }
+}
+
+void syncRaftRecordVote(SSyncRaftProgressTracker* tracker, int i, bool grant) {
+  if (tracker->votes[i] != SYNC_RAFT_VOTE_RESP_UNKNOWN) {
+    return;
+  }
+
+  tracker->votes[i] = grant ? SYNC_RAFT_VOTE_RESP_GRANT : SYNC_RAFT_VOTE_RESP_REJECT;
+}
+
+/** 
+ * syncRaftTallyVotes returns the number of granted and rejected Votes, and whether the
+ * election outcome is known.
+ **/
+SyncRaftVoteResult syncRaftTallyVotes(SSyncRaftProgressTracker* tracker, int* rejected, int *granted) {
+  int i;
+  SSyncRaftProgress* progress;
+  int r, g;
+
+  for (i = 0, r = 0, g = 0; i < TSDB_MAX_REPLICA; ++i) {
+    progress = &(tracker->progressMap[i]);
+    if (progress->id == SYNC_NON_NODE_ID) {
+      continue;
+    }
+
+    if (tracker->votes[i] == SYNC_RAFT_VOTE_RESP_UNKNOWN) {
+      continue;
+    }
+
+    if (tracker->votes[i] == SYNC_RAFT_VOTE_RESP_GRANT) {
+      g++;
+    } else {
+      r++;
+    }
+  }
+
+  if (rejected) *rejected = r;
+  if (granted) *granted = g;
+  return syncRaftVoteResult(&(tracker->config.voters), tracker->votes);
+}
\ No newline at end of file

source/libs/sync/src/sync_raft_quorum_joint.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "sync_raft_quorum_majority.h"
+#include "sync_raft_quorum_joint.h"
+#include "sync_raft_quorum.h"
+
+/**
+ * syncRaftVoteResult takes a mapping of voters to yes/no (true/false) votes and returns
+ * a result indicating whether the vote is pending, lost, or won. A joint quorum
+ * requires both majority quorums to vote in favor.
+ **/
+SyncRaftVoteResult syncRaftVoteResult(SSyncRaftQuorumJointConfig* config, const SyncRaftVoteResult* votes) {
+  SyncRaftVoteResult r1 = syncRaftMajorityVoteResult(&(config->majorityConfig[0]), votes);
+  SyncRaftVoteResult r2 = syncRaftMajorityVoteResult(&(config->majorityConfig[1]), votes);
+
+  if (r1 == r2) {
+    // If they agree, return the agreed state.
+    return r1;
+  }
+
+  if (r1 == SYNC_RAFT_VOTE_LOST || r2 == SYNC_RAFT_VOTE_LOST) {
+    // If either config has lost, loss is the only possible outcome.
+    return SYNC_RAFT_VOTE_LOST;
+  }
+
+  // One side won, the other one is pending, so the whole outcome is.
+  return SYNC_RAFT_VOTE_PENDING;
+}

source/libs/sync/src/sync_raft_quorum_majority.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <cli@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "sync_raft_quorum.h"
+#include "sync_raft_quorum_majority.h"
+
+/**
+ * syncRaftMajorityVoteResult takes a mapping of voters to yes/no (true/false) votes and returns
+ * a result indicating whether the vote is pending (i.e. neither a quorum of
+ * yes/no has been reached), won (a quorum of yes has been reached), or lost (a
+ * quorum of no has been reached).
+ **/
+SyncRaftVoteResult syncRaftMajorityVoteResult(SSyncCluster* config, const SyncRaftVoteResult* votes) {
+  if (config->replica == 0) {
+    return SYNC_RAFT_VOTE_WON;
+  }
+
+  int i, g, r, missing;
+  for (i = g = r = missing = 0; i < TSDB_MAX_REPLICA; ++i) {
+    if (config->nodeInfo[i].nodeId == SYNC_NON_NODE_ID) {
+      continue;
+    }
+
+    if (votes[i] == SYNC_RAFT_VOTE_RESP_UNKNOWN) {
+      missing += 1;
+    } else if (votes[i] == SYNC_RAFT_VOTE_RESP_GRANT) {
+      g +=1;
+    } else {
+      r += 1;
+    }
+  }
+
+  int quorum = config->replica / 2 + 1;
+  if (g >= quorum) {
+    return SYNC_RAFT_VOTE_WON;
+  }
+  if (r + missing >= quorum) {
+    return SYNC_RAFT_VOTE_PENDING;
+  }
+
+  return SYNC_RAFT_VOTE_LOST;
+}
\ No newline at end of file