[TD-10645][raft]<feature>refactor node and progress map

source/libs/sync/inc/sync_const.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_CONST_H
+#define _TD_LIBS_SYNC_CONST_H
+
+#include "sync.h"
+
+static int kSyncRaftMaxInflghtMsgs = 20;
+
+static SyncIndex kMaxCommitIndex = UINT64_MAX;
+
+#endif  /* _TD_LIBS_SYNC_CONST_H */

source/libs/sync/inc/sync_raft_inflights.h

@@ -18,54 +18,47 @@
 
 #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.
-**/
+// Inflights limits the number of MsgApp (represented by the largest index
+// contained within) sent to followers but not yet acknowledged by them. Callers
+// use Full() to check whether more messages can be sent, call Add() 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 */
+  // the starting index in the buffer
   int start;
 
-  /* number of inflights in the buffer */
+  // number of inflights in the buffer
   int count;
 
-  /* the size of the buffer */
+  // the size of the buffer
   int size;
 
-	/** 
-   * buffer contains the index of the last entry
-	 * inside one message.
-   **/
+	// buffer contains the index of the last entry
+	// inside one message.
   SyncIndex* buffer;
 } SSyncRaftInflights;
 
 SSyncRaftInflights* syncRaftOpenInflights(int size);
 void syncRaftCloseInflights(SSyncRaftInflights*);
 
+// reset frees all inflights.
 static FORCE_INLINE void syncRaftInflightReset(SSyncRaftInflights* inflights) {  
   inflights->count = 0;
   inflights->start = 0;
 }
 
+// Full returns true if no more messages can be sent at the moment.
 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.
- **/
+// Add notifies the Inflights that a new message with the given index is being
+// dispatched. Full() must be called prior to Add() to verify that there is room
+// for one more message, and consecutive calls to add Add() 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.
- **/
+// FreeLE frees the inflights smaller or equal to the given `to` flight.
 void syncRaftInflightFreeLE(SSyncRaftInflights* inflights, SyncIndex toIndex);
 
 /** 

source/libs/sync/inc/sync_raft_node_map.h

@@ -31,9 +31,9 @@ void syncRaftClearNodeMap(SSyncRaftNodeMap* nodeMap);
 
 bool syncRaftIsInNodeMap(const SSyncRaftNodeMap* nodeMap, SyncNodeId nodeId);
 
-void syncRaftCopyNodeMap(const SSyncRaftNodeMap* from, SSyncRaftNodeMap* to);
+void syncRaftCopyNodeMap(SSyncRaftNodeMap* from, SSyncRaftNodeMap* to);
 
-void syncRaftUnionNodeMap(const SSyncRaftNodeMap* nodeMap, SSyncRaftNodeMap* to);
+void syncRaftUnionNodeMap(SSyncRaftNodeMap* nodeMap, SSyncRaftNodeMap* to);
 
 void syncRaftAddToNodeMap(SSyncRaftNodeMap* nodeMap, SyncNodeId nodeId);
 

source/libs/sync/inc/sync_raft_progress.h

@@ -65,10 +65,13 @@ static const char* kProgressStateString[] = {
 	"Snapshot",
 };
 
-/**
- * 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.
- **/
+// 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.
+//
+// NB(tbg): Progress is basically a state machine whose transitions are mostly
+// strewn around `*raft.raft`. Additionally, some fields are only used when in a
+// certain State. All of this isn't ideal.
 struct SSyncRaftProgress {
 	SyncGroupId groupId;
 
@@ -80,63 +83,53 @@ struct SSyncRaftProgress {
 
   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.
-  **/
+	// 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.
   ESyncRaftProgressState 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.
-   **/
+	// PendingSnapshot is used in StateSnapshot.
+	// If there is a pending snapshot, the pendingSnapshot will be set to the
+	// index of the snapshot. If pendingSnapshot 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.
-   **/
+	// 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.
+	//
+	// TODO(tbg): the leader should always have this set to true.
   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().
-  **/
+	// 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.
-  **/
+	// 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.
-   **/
+	// IsLearner is true if this progress is tracked for a learner.
   bool isLearner;
 };
 
@@ -151,56 +144,44 @@ static FORCE_INLINE const char* syncRaftProgressStateString(const SSyncRaftProgr
 
 void syncRaftResetProgress(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.
- **/
+// BecomeProbe 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.
- **/ 
+// BecomeReplicate 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.
- **/
+// MaybeUpdate 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.
- **/
+// OptimisticUpdate 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.
-**/
+// MaybeDecrTo 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.
- **/
+// IsPaused 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) {
@@ -242,6 +223,8 @@ bool syncRaftIsInProgressMap(SSyncRaftProgressMap* progressMap, SyncNodeId id);
  **/
 bool syncRaftProgressIsUptodate(SSyncRaft* pRaft, SSyncRaftProgress* progress);
 
+// BecomeSnapshot moves the Progress to StateSnapshot with the specified pending
+// snapshot index.
 void syncRaftProgressBecomeSnapshot(SSyncRaftProgress* progress, SyncIndex snapshotIndex);
 
 void syncRaftCopyProgress(const SSyncRaftProgress* from, SSyncRaftProgress* to);

source/libs/sync/inc/sync_raft_progress_tracker.h

@@ -23,6 +23,7 @@
 #include "sync_raft_proto.h"
 #include "thash.h"
 
+// Config reflects the configuration tracked in a ProgressTracker.
 struct SSyncRaftProgressTrackerConfig {
   SSyncRaftQuorumJointConfig voters;
 
@@ -99,27 +100,32 @@ void syncRaftFreeTrackConfig(SSyncRaftProgressTrackerConfig* config);
 
 void syncRaftFreeTrackConfig(SSyncRaftProgressTrackerConfig* config);
 
+// ResetVotes prepares for a new round of vote counting via recordVote.
 void syncRaftResetVotes(SSyncRaftProgressTracker*);
 
 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).
- **/
+// RecordVote records that the node with the given id voted for this Raft
+// instance if v == true (and declined it otherwise).
 void syncRaftRecordVote(SSyncRaftProgressTracker* tracker, SyncNodeId id, bool grant);
 
 void syncRaftCopyTrackerConfig(const SSyncRaftProgressTrackerConfig* from, SSyncRaftProgressTrackerConfig* to);
 
 int syncRaftCheckTrackerConfigInProgress(SSyncRaftProgressTrackerConfig* config, SSyncRaftProgressMap* progressMap);
 
-/** 
- * syncRaftTallyVotes returns the number of granted and rejected Votes, and whether the
- * election outcome is known.
- **/
+// TallyVotes returns the number of granted and rejected Votes, and whether the
+// election outcome is known.
 ESyncRaftVoteResult syncRaftTallyVotes(SSyncRaftProgressTracker* tracker, int* rejected, int *granted);
 
-void syncRaftConfigState(const SSyncRaftProgressTracker* tracker, SSyncConfigState* cs);
+void syncRaftConfigState(SSyncRaftProgressTracker* tracker, SSyncConfigState* cs);
+
+// Committed returns the largest log index known to be committed based on what
+// the voting members of the group have acknowledged.
+SyncIndex syncRaftCommittedIndex(SSyncRaftProgressTracker* tracker);
+
+// QuorumActive returns true if the quorum is active from the view of the local
+// raft state machine. Otherwise, it returns false.
+bool syncRaftQuorumActive(SSyncRaftProgressTracker* tracker);
 
 bool syncRaftIsInNodeMap(const SSyncRaftNodeMap* nodeMap, SyncNodeId nodeId);
 

source/libs/sync/inc/sync_raft_quorum_joint.h

@@ -22,20 +22,25 @@
 #include "sync_raft_node_map.h"
 #include "thash.h"
 
-/**
- * SSyncRaftQuorumJointConfig is a configuration of two groups of (possibly overlapping)
- * majority configurations. Decisions require the support of both majorities.
- **/
+// JointConfig is a configuration of two groups of (possibly overlapping)
+// majority configurations. Decisions require the support of both majorities.
 typedef struct SSyncRaftQuorumJointConfig {
   SSyncRaftNodeMap outgoing;
   SSyncRaftNodeMap incoming;
 } 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.
- **/
+// IDs returns a newly initialized map representing the set of voters present
+// in the joint configuration.
+void syncRaftJointConfigIDs(SSyncRaftQuorumJointConfig* config, SSyncRaftNodeMap* nodeMap);
+
+// CommittedIndex returns the largest committed index for the given joint
+// quorum. An index is jointly committed if it is committed in both constituent
+// majorities.
+SyncIndex syncRaftJointConfigCommittedIndex(const SSyncRaftQuorumJointConfig* config, matchAckIndexerFp indexer, void* arg);
+
+// VoteResult 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.
 ESyncRaftVoteType syncRaftVoteResult(SSyncRaftQuorumJointConfig* config, SHashObj* votesMap);
 
 void syncRaftInitQuorumJointConfig(SSyncRaftQuorumJointConfig* config);
@@ -76,6 +81,4 @@ static FORCE_INLINE bool syncRaftJointConfigIsInOutgoing(const SSyncRaftQuorumJo
   return syncRaftIsInNodeMap(&config->outgoing, id);
 }
 
-void syncRaftJointConfigIDS(const SSyncRaftQuorumJointConfig* config, SSyncRaftNodeMap* nodeMap);
-
 #endif /* _TD_LIBS_SYNC_RAFT_QUORUM_JOINT_H */

source/libs/sync/inc/sync_raft_quorum_majority.h

@@ -29,4 +29,8 @@
  **/
 ESyncRaftVoteResult syncRaftMajorityVoteResult(SSyncRaftNodeMap* config, SHashObj* votesMap);
 
+// CommittedIndex computes the committed index from those supplied via the
+// provided AckedIndexer (for the active config).
+SyncIndex syncRaftMajorityConfigCommittedIndex(const SSyncRaftNodeMap* config, matchAckIndexerFp indexer, void* arg);
+
 #endif /* _TD_LIBS_SYNC_RAFT_QUORUM_MAJORITY_H */

source/libs/sync/inc/sync_type.h

@@ -86,4 +86,6 @@ typedef enum {
 
 typedef void (*visitProgressFp)(SSyncRaftProgress* progress, void* arg);
 
+typedef void (*matchAckIndexerFp)(SyncNodeId id, void* arg, SyncIndex* index);
+
 #endif  /* _TD_LIBS_SYNC_TYPE_H */

source/libs/sync/src/sync_raft_election.c

@@ -84,7 +84,7 @@ static void campaign(SSyncRaft* pRaft, ESyncRaftElectionType cType) {
   SyncIndex lastIndex = syncRaftLogLastIndex(pRaft->log);
   SyncTerm lastTerm = syncRaftLogLastTerm(pRaft->log);
   SSyncRaftNodeMap nodeMap;
-  syncRaftJointConfigIDS(&pRaft->tracker->config.voters, &nodeMap);
+  syncRaftJointConfigIDs(&pRaft->tracker->config.voters, &nodeMap);
   SyncNodeId *pNodeId = NULL;
   while (!syncRaftIterateNodeMap(&nodeMap, pNodeId)) {
     SyncNodeId nodeId = *pNodeId;

source/libs/sync/src/sync_raft_inflights.c

@@ -40,19 +40,16 @@ void syncRaftCloseInflights(SSyncRaftInflights* inflights) {
   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.
- **/
+// Add notifies the Inflights that a new message with the given index is being
+// dispatched. Full() must be called prior to Add() to verify that there is room
+// for one more message, and consecutive calls to add Add() 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;
   }
@@ -61,12 +58,10 @@ void syncRaftInflightAdd(SSyncRaftInflights* inflights, SyncIndex inflightIndex)
   inflights->count++;
 }
 
-/**
- * syncRaftInflightFreeLE frees the inflights smaller or equal to the given `to` flight.
- **/
+// FreeLE 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 */
+    // out of the left side of the window
     return;
   }
 
@@ -95,10 +90,8 @@ void syncRaftInflightFreeLE(SSyncRaftInflights* inflights, SyncIndex toIndex) {
   }
 }
 
-/** 
- * syncRaftInflightFreeFirstOne releases the first inflight. 
- * This is a no-op if nothing is inflight.
- **/
+// FreeFirstOne 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_node_map.c

@@ -37,11 +37,10 @@ bool syncRaftIsInNodeMap(const SSyncRaftNodeMap* nodeMap, SyncNodeId nodeId) {
   return true;
 }
 
-void syncRaftCopyNodeMap(const SSyncRaftNodeMap* from, SSyncRaftNodeMap* to) {
-  SyncNodeId** ppId = (SyncNodeId**)taosHashIterate(from->nodeIdMap, NULL);
-  while (ppId) {
-    taosHashPut(to->nodeIdMap, ppId, sizeof(SyncNodeId*), ppId, sizeof(SyncNodeId*));
-    ppId = taosHashIterate(from->nodeIdMap, ppId);
+void syncRaftCopyNodeMap(SSyncRaftNodeMap* from, SSyncRaftNodeMap* to) {
+  SyncNodeId *pId = NULL;
+  while (!syncRaftIterateNodeMap(from, pId)) {
+    taosHashPut(to->nodeIdMap, &pId, sizeof(SyncNodeId*), &pId, sizeof(SyncNodeId*));
   }
 }
 
@@ -66,7 +65,7 @@ bool syncRaftIsAllNodeInProgressMap(SSyncRaftNodeMap* nodeMap, SSyncRaftProgress
   return true;
 }
 
-void syncRaftUnionNodeMap(const SSyncRaftNodeMap* nodeMap, SSyncRaftNodeMap* to) {
+void syncRaftUnionNodeMap(SSyncRaftNodeMap* nodeMap, SSyncRaftNodeMap* to) {
   syncRaftCopyNodeMap(nodeMap, to);
 }
 

source/libs/sync/src/sync_raft_progress.c

@@ -47,11 +47,9 @@ void syncRaftResetProgress(SSyncRaft* pRaft, 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.
- **/
+// MaybeUpdate 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;
 
@@ -66,27 +64,36 @@ bool syncRaftProgressMaybeUpdate(SSyncRaftProgress* progress, SyncIndex lastInde
   return updated;
 }
 
+// MaybeDecrTo 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) {
   if (progress->state == PROGRESS_STATE_REPLICATE) {
-		/** 
-     * the rejection must be stale if the progress has matched and "rejected"
-		 * is smaller than "match".
-     **/
+		// 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 */
+		// Directly decrease next to match + 1.
+		//
+		// TODO(tbg): why not use matchHint if it's larger?
     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.
-   **/
+	// 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);
@@ -99,14 +106,12 @@ bool syncRaftProgressMaybeDecrTo(SSyncRaftProgress* progress,
   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.
- **/
+// IsPaused 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:
@@ -152,16 +157,12 @@ 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.
- **/
+// BecomeProbe 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 the original state is StateSnapshot, 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);
@@ -172,14 +173,14 @@ void syncRaftProgressBecomeProbe(SSyncRaftProgress* progress) {
   }
 }
 
-/**
- * syncRaftProgressBecomeReplicate transitions into StateReplicate, resetting Next to Match+1.
- **/
+// BecomeReplicate transitions into StateReplicate, resetting Next to Match+1.
 void syncRaftProgressBecomeReplicate(SSyncRaftProgress* progress) {
   resetProgressState(progress, PROGRESS_STATE_REPLICATE);
   progress->nextIndex = progress->matchIndex + 1;
 }
 
+// BecomeSnapshot moves the Progress to StateSnapshot with the specified pending
+// snapshot index.
 void syncRaftProgressBecomeSnapshot(SSyncRaftProgress* progress, SyncIndex snapshotIndex) {
   resetProgressState(progress, PROGRESS_STATE_SNAPSHOT);
   progress->pendingSnapshotIndex = snapshotIndex;
@@ -242,10 +243,8 @@ static void unrefProgress(SSyncRaftProgress* progress, void* arg) {
   }
 }
  
-/**
- * ResetState moves the Progress into the specified State, resetting ProbeSent,
- * PendingSnapshot, and Inflights.
- **/
+// ResetState moves the Progress into the specified State, resetting ProbeSent,
+// PendingSnapshot, and Inflights.
 static void resetProgressState(SSyncRaftProgress* progress, ESyncRaftProgressState state) {
   progress->probeSent = false;
   progress->pendingSnapshotIndex = 0;
@@ -253,83 +252,9 @@ static void resetProgressState(SSyncRaftProgress* progress, ESyncRaftProgressSta
   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.
- **/
+// 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;
-}
-
-ESyncRaftProgressState 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

@@ -13,6 +13,8 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include "raft.h"
+#include "sync_const.h"
 #include "sync_raft_progress_tracker.h"
 #include "sync_raft_proto.h"
 
@@ -22,9 +24,11 @@ SSyncRaftProgressTracker* syncRaftOpenProgressTracker(SSyncRaft* pRaft) {
     return NULL;
   }
 
+  tracker->votesMap = taosHashInit(TSDB_MAX_REPLICA, taosGetDefaultHashFunction(TSDB_DATA_TYPE_INT), true, HASH_ENTRY_LOCK);
+
   syncRaftInitTrackConfig(&tracker->config);
-  syncRaftInitNodeMap(&tracker->config.learnersNext);
   tracker->pRaft = pRaft;
+  tracker->maxInflightMsgs = kSyncRaftMaxInflghtMsgs;
 
   return tracker;
 }
@@ -39,9 +43,11 @@ void syncRaftInitTrackConfig(SSyncRaftProgressTrackerConfig* config) {
 void syncRaftFreeTrackConfig(SSyncRaftProgressTrackerConfig* config) {
   syncRaftFreeNodeMap(&config->learners);
   syncRaftFreeNodeMap(&config->learnersNext);
-  syncRaftFreeQuorumJointConfig(&config->voters);
+  syncRaftFreeNodeMap(&config->voters.incoming);
+  syncRaftFreeNodeMap(&config->voters.outgoing);
 }
 
+// ResetVotes prepares for a new round of vote counting via recordVote.
 void syncRaftResetVotes(SSyncRaftProgressTracker* tracker) {
   taosHashClear(tracker->votesMap);
 }
@@ -50,14 +56,15 @@ void syncRaftProgressVisit(SSyncRaftProgressTracker* tracker, visitProgressFp vi
   syncRaftVisitProgressMap(&tracker->progressMap, visit, arg);  
 }
 
+// RecordVote records that the node with the given id voted for this Raft
+// instance if v == true (and declined it otherwise).
 void syncRaftRecordVote(SSyncRaftProgressTracker* tracker, SyncNodeId id, bool grant) {
   ESyncRaftVoteType* pType = taosHashGet(tracker->votesMap, &id, sizeof(SyncNodeId*));
   if (pType != NULL) {
     return;
   }
 
-  ESyncRaftVoteType type = grant ? SYNC_RAFT_VOTE_RESP_GRANT : SYNC_RAFT_VOTE_RESP_REJECT;
-  taosHashPut(tracker->votesMap, &id, sizeof(SyncNodeId), &type, sizeof(ESyncRaftVoteType*));
+  taosHashPut(tracker->votesMap, &id, sizeof(SyncNodeId), &grant, sizeof(bool*));
 }
 
 void syncRaftCopyTrackerConfig(const SSyncRaftProgressTrackerConfig* from, SSyncRaftProgressTrackerConfig* to) {
@@ -78,26 +85,27 @@ int syncRaftCheckTrackerConfigInProgress(SSyncRaftProgressTrackerConfig* config,
   return 0;
 }
 
-/** 
- * syncRaftTallyVotes returns the number of granted and rejected Votes, and whether the
- * election outcome is known.
- **/
+// TallyVotes returns the number of granted and rejected Votes, and whether the
+// election outcome is known.
 ESyncRaftVoteResult syncRaftTallyVotes(SSyncRaftProgressTracker* tracker, int* rejected, int *granted) {
-  int i;
-  SSyncRaftProgress* progress;
+  SSyncRaftProgress* progress = NULL;
   int r, g;
 
+	// Make sure to populate granted/rejected correctly even if the Votes slice
+	// contains members no longer part of the configuration. This doesn't really
+	// matter in the way the numbers are used (they're informational), but might
+	// as well get it right.
   while (!syncRaftIterateProgressMap(&tracker->progressMap, progress)) {
     if (progress->id == SYNC_NON_NODE_ID) {
       continue;
     }
 
-    ESyncRaftVoteType* pType = taosHashGet(tracker->votesMap, &progress->id, sizeof(SyncNodeId*));
-    if (pType == NULL) {
+    bool* v = taosHashGet(tracker->votesMap, &progress->id, sizeof(SyncNodeId*));
+    if (v == NULL) {
       continue;
     }
 
-    if (*pType == SYNC_RAFT_VOTE_RESP_GRANT) {
+    if (*v) {
       g++;
     } else {
       r++;
@@ -109,9 +117,40 @@ ESyncRaftVoteResult syncRaftTallyVotes(SSyncRaftProgressTracker* tracker, int* r
   return syncRaftVoteResult(&(tracker->config.voters), tracker->votesMap);
 }
 
-void syncRaftConfigState(const SSyncRaftProgressTracker* tracker, SSyncConfigState* cs) {
+void syncRaftConfigState(SSyncRaftProgressTracker* tracker, SSyncConfigState* cs) {
   syncRaftCopyNodeMap(&tracker->config.voters.incoming, &cs->voters);
   syncRaftCopyNodeMap(&tracker->config.voters.outgoing, &cs->votersOutgoing);
   syncRaftCopyNodeMap(&tracker->config.learners, &cs->learners);
   syncRaftCopyNodeMap(&tracker->config.learnersNext, &cs->learnersNext);
+  cs->autoLeave = tracker->config.autoLeave;
+}
+
+static void matchAckIndexer(SyncNodeId id, void* arg, SyncIndex* index) {
+  SSyncRaftProgressTracker* tracker = (SSyncRaftProgressTracker*)arg;
+  SSyncRaftProgress* progress = syncRaftFindProgressByNodeId(&tracker->progressMap, id);
+  if (progress == NULL) {
+    *index = 0;
+    return;
+  }
+  *index = progress->matchIndex;
+}
+
+// Committed returns the largest log index known to be committed based on what
+// the voting members of the group have acknowledged.
+SyncIndex syncRaftCommittedIndex(SSyncRaftProgressTracker* tracker) {
+  return syncRaftJointConfigCommittedIndex(&tracker->config.voters, matchAckIndexer, tracker);
+}
+
+static void visitProgressActive(SSyncRaftProgress* progress, void* arg) {
+  SHashObj* votesMap = (SHashObj*)arg;
+  taosHashPut(votesMap, &progress->id, sizeof(SyncNodeId), &progress->recentActive, sizeof(bool));
+}
+
+// QuorumActive returns true if the quorum is active from the view of the local
+// raft state machine. Otherwise, it returns false.
+bool syncRaftQuorumActive(SSyncRaftProgressTracker* tracker) {
+  SHashObj* votesMap = taosHashInit(TSDB_MAX_REPLICA, taosGetDefaultHashFunction(TSDB_DATA_TYPE_INT), true, HASH_ENTRY_LOCK);
+  syncRaftVisitProgressMap(&tracker->progressMap, visitProgressActive, votesMap);
+
+  return syncRaftVoteResult(&tracker->config.voters, votesMap) == SYNC_RAFT_VOTE_WON;
 }
\ No newline at end of file

source/libs/sync/src/sync_raft_quorum_joint.c

@@ -59,8 +59,17 @@ void syncRaftJointConfigRemoveFromIncoming(SSyncRaftQuorumJointConfig* config, S
   syncRaftRemoveFromNodeMap(&config->incoming, id);
 }
 
-void syncRaftJointConfigIDS(const SSyncRaftQuorumJointConfig* config, SSyncRaftNodeMap* nodeMap) {
+void syncRaftJointConfigIDs(SSyncRaftQuorumJointConfig* config, SSyncRaftNodeMap* nodeMap) {
   syncRaftCopyNodeMap(&config->incoming, nodeMap);
 
   syncRaftUnionNodeMap(&config->outgoing, nodeMap);
+}
+
+SyncIndex syncRaftJointConfigCommittedIndex(const SSyncRaftQuorumJointConfig* config, matchAckIndexerFp indexer, void* arg) {
+  SyncIndex index0, index1;
+
+  index0 = syncRaftMajorityConfigCommittedIndex(&config->incoming, indexer, arg);
+  index1 = syncRaftMajorityConfigCommittedIndex(&config->outgoing, indexer, arg);
+
+  return index0 < index1 ? index0 : index1;
 }
\ No newline at end of file

source/libs/sync/src/sync_raft_quorum_majority.c

@@ -13,6 +13,7 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include "sync_const.h"
 #include "sync_raft_quorum.h"
 #include "sync_raft_quorum_majority.h"
 #include "sync_raft_node_map.h"
@@ -34,13 +35,13 @@ ESyncRaftVoteResult syncRaftMajorityVoteResult(SSyncRaftNodeMap* config, SHashOb
   i = g = r = missing = 0;
   SyncNodeId* pId = NULL;
   while (!syncRaftIterateNodeMap(config, pId)) {
-    const ESyncRaftVoteType* pType = taosHashGet(votesMap, pId, sizeof(SyncNodeId*));
-    if (pType == NULL) {
+    const bool* v = (const bool*)taosHashGet(votesMap, pId, sizeof(SyncNodeId*));
+    if (v == NULL) {
       missing += 1;
       continue;
     }
 
-    if (*pType == SYNC_RAFT_VOTE_RESP_GRANT) {
+    if (*v) {
       g +=1;
     } else {
       r += 1;
@@ -56,4 +57,65 @@ ESyncRaftVoteResult syncRaftMajorityVoteResult(SSyncRaftNodeMap* config, SHashOb
   }
 
   return SYNC_RAFT_VOTE_LOST;
+}
+
+int compSyncIndex(const void * elem1, const void * elem2) {
+  SyncIndex index1 = *((SyncIndex*)elem1);
+  SyncIndex index2 = *((SyncIndex*)elem1);
+  if (index1 > index2) return  1;
+  if (index1 < index2) return -1;
+  return 0;
+}
+
+SyncIndex syncRaftMajorityConfigCommittedIndex(const SSyncRaftNodeMap* config, matchAckIndexerFp indexer, void* arg) {
+  int n = syncRaftNodeMapSize(config);
+  if (n == 0) {
+		// This plays well with joint quorums which, when one half is the zero
+		// MajorityConfig, should behave like the other half.    
+    return kMaxCommitIndex;
+  }
+
+	// Use an on-stack slice to collect the committed indexes when n <= 7
+	// (otherwise we alloc). The alternative is to stash a slice on
+	// MajorityConfig, but this impairs usability (as is, MajorityConfig is just
+	// a map, and that's nice). The assumption is that running with a
+	// replication factor of >7 is rare, and in cases in which it happens
+	// performance is a lesser concern (additionally the performance
+	// implications of an allocation here are far from drastic).
+  SyncIndex* srt = NULL;
+  SyncIndex srk[TSDB_MAX_REPLICA];
+  if (n > TSDB_MAX_REPLICA) {
+    srt = (SyncIndex*)malloc(sizeof(SyncIndex) * n);
+    if (srt == NULL) {
+      return kMaxCommitIndex;
+    }
+  } else {
+    srt = &srk[0];
+  }
+
+	// Fill the slice with the indexes observed. Any unused slots will be
+	// left as zero; these correspond to voters that may report in, but
+	// haven't yet. We fill from the right (since the zeroes will end up on
+	// the left after sorting below anyway).
+  SyncNodeId *pId = NULL;
+  int i = 0;
+  SyncIndex index;
+  while (!syncRaftIterateNodeMap(config, pId)) {
+    indexer(*pId, arg, &index);    
+    srt[i++] = index;
+  }
+
+	// Sort by index. Use a bespoke algorithm (copied from the stdlib's sort
+	// package) to keep srt on the stack.
+  qsort(srt, n, sizeof(SyncIndex), compSyncIndex);
+
+	// The smallest index into the array for which the value is acked by a
+	// quorum. In other words, from the end of the slice, move n/2+1 to the
+	// left (accounting for zero-indexing).
+  index = srt[n - (n/2 + 1)];
+  if (srt != &srk[0]) {
+    free(srt);
+  }
+
+  return index;
 }
\ No newline at end of file