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

source/libs/sync/inc/sync_raft_config_change.h

@@ -33,6 +33,11 @@ struct SSyncRaftChanger {
 typedef int (*configChangeFp)(SSyncRaftChanger* changer, const SSyncConfChangeSingleArray* css,
                             SSyncRaftProgressTrackerConfig* config, SSyncRaftProgressMap* progressMap);
 
+// Simple carries out a series of configuration changes that (in aggregate)
+// mutates the incoming majority config Voters[0] by at most one. This method
+// will return an error if that is not the case, if the resulting quorum is
+// zero, or if the configuration is in a joint state (i.e. if there is an
+// outgoing configuration).
 int syncRaftChangerSimpleConfig(SSyncRaftChanger* changer, const SSyncConfChangeSingleArray* css,
                             SSyncRaftProgressTrackerConfig* config, SSyncRaftProgressMap* progressMap);
 

source/libs/sync/inc/sync_raft_node_map.h

@@ -25,6 +25,7 @@ struct SSyncRaftNodeMap {
 };
 
 void syncRaftInitNodeMap(SSyncRaftNodeMap* nodeMap);
+void syncRaftFreeNodeMap(SSyncRaftNodeMap* nodeMap);
 
 void syncRaftClearNodeMap(SSyncRaftNodeMap* nodeMap);
 
@@ -43,6 +44,6 @@ int32_t syncRaftNodeMapSize(const SSyncRaftNodeMap* nodeMap);
 // return true if reach the end
 bool syncRaftIterateNodeMap(const SSyncRaftNodeMap* nodeMap, SyncNodeId *pId);
 
-bool syncRaftIsAllInProgressMap(const SSyncRaftNodeMap* nodeMap, const SSyncRaftProgressMap* progressMap);
+bool syncRaftIsAllNodeInProgressMap(SSyncRaftNodeMap* nodeMap, SSyncRaftProgressMap* progressMap);
 
 #endif /* _TD_LIBS_SYNC_RAFT_NODE_MAP_H */
\ No newline at end of file

source/libs/sync/inc/sync_raft_progress.h

@@ -74,6 +74,8 @@ struct SSyncRaftProgress {
 
 	SyncNodeId id;
 
+	int16_t refCount;
+
   SyncIndex nextIndex;
 
   SyncIndex matchIndex;
@@ -221,6 +223,12 @@ static FORCE_INLINE bool syncRaftProgressRecentActive(SSyncRaftProgress* progres
   return progress->recentActive;
 }
 
+void syncRaftInitProgressMap(SSyncRaftProgressMap* progressMap);
+void syncRaftFreeProgressMap(SSyncRaftProgressMap* progressMap);
+
+void syncRaftClearProgressMap(SSyncRaftProgressMap* progressMap);
+void syncRaftCopyProgressMap(SSyncRaftProgressMap* from, SSyncRaftProgressMap* to);
+
 SSyncRaftProgress* syncRaftFindProgressByNodeId(const SSyncRaftProgressMap* progressMap, SyncNodeId id);
 
 int syncRaftAddToProgressMap(SSyncRaftProgressMap* progressMap, SSyncRaftProgress* progress);

source/libs/sync/inc/sync_raft_progress_tracker.h

@@ -94,6 +94,11 @@ struct SSyncRaftProgressTracker {
 
 SSyncRaftProgressTracker* syncRaftOpenProgressTracker(SSyncRaft* pRaft);
 
+void syncRaftInitTrackConfig(SSyncRaftProgressTrackerConfig* config);
+void syncRaftFreeTrackConfig(SSyncRaftProgressTrackerConfig* config);
+
+void syncRaftFreeTrackConfig(SSyncRaftProgressTrackerConfig* config);
+
 void syncRaftResetVotes(SSyncRaftProgressTracker*);
 
 void syncRaftProgressVisit(SSyncRaftProgressTracker*, visitProgressFp visit, void* arg);
@@ -104,9 +109,9 @@ void syncRaftProgressVisit(SSyncRaftProgressTracker*, visitProgressFp visit, voi
  **/
 void syncRaftRecordVote(SSyncRaftProgressTracker* tracker, SyncNodeId id, bool grant);
 
-void syncRaftCloneTrackerConfig(const SSyncRaftProgressTrackerConfig* config, SSyncRaftProgressTrackerConfig* result);
+void syncRaftCopyTrackerConfig(const SSyncRaftProgressTrackerConfig* from, SSyncRaftProgressTrackerConfig* to);
 
-int syncRaftCheckProgress(const SSyncRaftProgressTrackerConfig* config, SSyncRaftProgressMap* progressMap);
+int syncRaftCheckTrackerConfigInProgress(SSyncRaftProgressTrackerConfig* config, SSyncRaftProgressMap* progressMap);
 
 /** 
  * syncRaftTallyVotes returns the number of granted and rejected Votes, and whether the

source/libs/sync/inc/sync_raft_proto.h

@@ -59,4 +59,19 @@ typedef struct SSyncConfigState {
   bool autoLeave;
 } SSyncConfigState;
 
+static FORCE_INLINE bool syncRaftConfArrayIsEmpty(const SSyncConfChangeSingleArray* ary) {
+  return ary->n == 0;
+}
+
+static FORCE_INLINE void syncRaftInitConfArray(SSyncConfChangeSingleArray* ary) {
+  *ary = (SSyncConfChangeSingleArray) {
+    .changes = NULL,
+    .n       = 0,
+  };
+}
+
+static FORCE_INLINE void syncRaftFreeConfArray(SSyncConfChangeSingleArray* ary) {
+  if (ary->changes != NULL) free(ary->changes);
+}
+
 #endif /* TD_SYNC_RAFT_PROTO_H */

source/libs/sync/inc/sync_raft_quorum_joint.h

@@ -38,6 +38,8 @@ typedef struct SSyncRaftQuorumJointConfig {
  **/
 ESyncRaftVoteType syncRaftVoteResult(SSyncRaftQuorumJointConfig* config, SHashObj* votesMap);
 
+void syncRaftInitQuorumJointConfig(SSyncRaftQuorumJointConfig* config);
+
 static FORCE_INLINE bool syncRaftJointConfigInOutgoing(const SSyncRaftQuorumJointConfig* config, SyncNodeId id) {
   return syncRaftIsInNodeMap(&config->outgoing, id);
 }

source/libs/sync/inc/sync_raft_restore.h

@@ -27,6 +27,7 @@
 // the Changer only needs a ProgressMap (not a whole Tracker) at which point
 // this can just take LastIndex and MaxInflight directly instead and cook up
 // the results from that alone.
-int syncRaftRestoreConfig(SSyncRaftChanger* changer, const SSyncConfigState* cs);
+int syncRaftRestoreConfig(SSyncRaftChanger* changer, const SSyncConfigState* cs,
+                          SSyncRaftProgressTrackerConfig* config, SSyncRaftProgressMap* progressMap);
 
 #endif /* TD_SYNC_RAFT_RESTORE_H */

source/libs/sync/src/raft.c

@@ -101,11 +101,22 @@ int32_t syncRaftStart(SSyncRaft* pRaft, const SSyncInfo* pInfo) {
     .tracker = pRaft->tracker,
     .lastIndex = syncRaftLogLastIndex(pRaft->log),
   };
-  if (syncRaftRestoreConfig(&changer, &confState) < 0) {
+  SSyncRaftProgressTrackerConfig config;
+  SSyncRaftProgressMap progressMap;
+
+  if (syncRaftRestoreConfig(&changer, &confState, &config, &progressMap) < 0) {
     syncError("syncRaftRestoreConfig for vgid %d fail", pInfo->vgId);
     return -1;
   }
 
+  // save restored config and progress map to tracker
+  syncRaftCopyProgressMap(&progressMap, &pRaft->tracker->progressMap);
+  syncRaftCopyTrackerConfig(&config, &pRaft->tracker->config);
+
+  // free progress map and config
+  syncRaftFreeProgressMap(&progressMap);
+  syncRaftFreeTrackConfig(&config);
+
   if (!syncRaftIsEmptyServerState(&serverState)) {
     syncRaftLoadState(pRaft, &serverState);
   }

source/libs/sync/src/sync_raft_config_change.c

@@ -92,7 +92,7 @@ int syncRaftChangerEnterJoint(SSyncRaftChanger* changer, bool autoLeave, const S
   return checkAndReturn(config, progressMap);
 }
 
-// syncRaftChangerSimpleConfig carries out a series of configuration changes that (in aggregate)
+// Simple carries out a series of configuration changes that (in aggregate)
 // mutates the incoming majority config Voters[0] by at most one. This method
 // will return an error if that is not the case, if the resulting quorum is
 // zero, or if the configuration is in a joint state (i.e. if there is an
@@ -275,7 +275,8 @@ static void initProgress(SSyncRaftChanger* changer, SSyncRaftProgressTrackerConf
 		// When a node is first added, we should mark it as recently active.
 		// Otherwise, CheckQuorum may cause us to step down if it is invoked
 		// before the added node has had a chance to communicate with us.  
-    .recentActive = true,    
+    .recentActive = true,  
+    .refCount = 0,  
   };
 
   syncRaftAddToProgressMap(progressMap, pProgress);
@@ -285,7 +286,7 @@ static void initProgress(SSyncRaftChanger* changer, SSyncRaftProgressTrackerConf
 // each other. This is used to check both what the Changer is initialized with,
 // as well as what it returns.
 static int checkInvariants(SSyncRaftProgressTrackerConfig* config, SSyncRaftProgressMap* progressMap) {
-  int ret = syncRaftCheckProgress(config, progressMap);
+  int ret = syncRaftCheckTrackerConfigInProgress(config, progressMap);
   if (ret != 0) {
     return ret;
   }
@@ -296,6 +297,7 @@ static int checkInvariants(SSyncRaftProgressTrackerConfig* config, SSyncRaftProg
   while (!syncRaftIterateNodeMap(&config->learnersNext, pNodeId)) {
     SyncNodeId nodeId = *pNodeId;
     if (!syncRaftJointConfigInOutgoing(&config->voters, nodeId)) {
+      syncError("[%d] is in LearnersNext, but not outgoing", nodeId);
       return -1;
     }
     SSyncRaftProgress* progress = syncRaftFindProgressByNodeId(progressMap, nodeId);
@@ -311,8 +313,8 @@ static int checkInvariants(SSyncRaftProgressTrackerConfig* config, SSyncRaftProg
   pNodeId = NULL;
   while (!syncRaftIterateNodeMap(&config->learners, pNodeId)) {
     SyncNodeId nodeId = *pNodeId;
-    if (syncRaftJointConfigInIncoming(&config->voters, nodeId)) {
-      syncError("%d is in Learners and voter.incoming", nodeId);
+    if (syncRaftJointConfigInOutgoing(&config->voters, nodeId)) {
+      syncError("%d is in Learners and outgoing", nodeId);
       return -1;
     }
     SSyncRaftProgress* progress = syncRaftFindProgressByNodeId(progressMap, nodeId);
@@ -327,7 +329,7 @@ static int checkInvariants(SSyncRaftProgressTrackerConfig* config, SSyncRaftProg
 
   if (!hasJointConfig(config)) {
     // We enforce that empty maps are nil instead of zero.
-    if (syncRaftNodeMapSize(&config->learnersNext)) {
+    if (syncRaftNodeMapSize(&config->learnersNext) > 0) {
       syncError("cfg.LearnersNext must be nil when not joint");
       return -1;
     }
@@ -344,8 +346,8 @@ static int checkInvariants(SSyncRaftProgressTrackerConfig* config, SSyncRaftProg
 // the purposes of the Changer) and returns those copies. It returns an error
 // if checkInvariants does.
 static int checkAndCopy(SSyncRaftChanger* changer, SSyncRaftProgressTrackerConfig* config, SSyncRaftProgressMap* progressMap) {
-  syncRaftCloneTrackerConfig(&changer->tracker->config, config);
-  int i;
+  syncRaftCopyTrackerConfig(&changer->tracker->config, config);
+  syncRaftClearProgressMap(progressMap);
 
   SSyncRaftProgress* pProgress = NULL;
   while (!syncRaftIterateProgressMap(&changer->tracker->progressMap, pProgress)) {

source/libs/sync/src/sync_raft_node_map.c

@@ -21,6 +21,10 @@ void syncRaftInitNodeMap(SSyncRaftNodeMap* nodeMap) {
   nodeMap->nodeIdMap = taosHashInit(TSDB_MAX_REPLICA, taosGetDefaultHashFunction(TSDB_DATA_TYPE_INT), true, HASH_ENTRY_LOCK);
 }
 
+void syncRaftFreeNodeMap(SSyncRaftNodeMap* nodeMap) {
+  taosHashCleanup(nodeMap->nodeIdMap);
+}
+
 void syncRaftClearNodeMap(SSyncRaftNodeMap* nodeMap) {
   taosHashClear(nodeMap->nodeIdMap);
 }
@@ -51,7 +55,7 @@ bool syncRaftIterateNodeMap(const SSyncRaftNodeMap* nodeMap, SyncNodeId *pId) {
   return false;
 }
 
-bool syncRaftIsAllInProgressMap(const SSyncRaftNodeMap* nodeMap, const SSyncRaftProgressMap* progressMap) {
+bool syncRaftIsAllNodeInProgressMap(SSyncRaftNodeMap* nodeMap, SSyncRaftProgressMap* progressMap) {
   SyncNodeId *pId = NULL;
   while (!syncRaftIterateNodeMap(nodeMap, pId)) {
     if (!syncRaftIsInProgressMap(progressMap, *pId)) {

source/libs/sync/src/sync_raft_progress.c

@@ -20,6 +20,11 @@
 #include "sync.h"
 #include "syncInt.h"
 
+static void copyProgress(SSyncRaftProgress* progress, void* arg);
+
+static void refProgress(SSyncRaftProgress* progress);
+static void unrefProgress(SSyncRaftProgress* progress, void*);
+
 static void resetProgressState(SSyncRaftProgress* progress, ESyncRaftProgressState state);
 static void probeAcked(SSyncRaftProgress* progress);
 
@@ -125,6 +130,7 @@ SSyncRaftProgress* syncRaftFindProgressByNodeId(const SSyncRaftProgressMap* prog
 }
 
 int syncRaftAddToProgressMap(SSyncRaftProgressMap* progressMap, SSyncRaftProgress* progress) {
+  refProgress(progress);
   taosHashPut(progressMap->progressMap, &progress->id, sizeof(SyncNodeId*), &progress, sizeof(SSyncRaftProgress*));
 }
 
@@ -133,7 +139,8 @@ void syncRaftRemoveFromProgressMap(SSyncRaftProgressMap* progressMap, SyncNodeId
   if (ppProgress == NULL) {
     return;
   }
-  free(*ppProgress);
+  unrefProgress(*ppProgress, NULL);
+
   taosHashRemove(progressMap->progressMap, &id, sizeof(SyncNodeId*));
 }
 
@@ -182,6 +189,23 @@ void syncRaftCopyProgress(const SSyncRaftProgress* progress, SSyncRaftProgress*
   memcpy(out, progress, sizeof(SSyncRaftProgress));
 }
 
+void syncRaftInitProgressMap(SSyncRaftProgressMap* progressMap) {
+  progressMap->progressMap = taosHashInit(TSDB_MAX_REPLICA, taosGetDefaultHashFunction(TSDB_DATA_TYPE_INT), true, HASH_ENTRY_LOCK);
+}
+
+void syncRaftFreeProgressMap(SSyncRaftProgressMap* progressMap) {
+  syncRaftVisitProgressMap(progressMap, unrefProgress, NULL);
+  taosHashCleanup(progressMap->progressMap);
+}
+
+void syncRaftClearProgressMap(SSyncRaftProgressMap* progressMap) {
+  taosHashClear(progressMap->progressMap);
+}
+
+void syncRaftCopyProgressMap(SSyncRaftProgressMap* from, SSyncRaftProgressMap* to) {
+  syncRaftVisitProgressMap(from, copyProgress, to);
+}
+
 bool syncRaftIterateProgressMap(const SSyncRaftProgressMap* progressMap, SSyncRaftProgress *pProgress) {
   SSyncRaftProgress **ppProgress = taosHashIterate(progressMap->progressMap, pProgress);
   if (ppProgress == NULL) {
@@ -199,6 +223,25 @@ bool syncRaftVisitProgressMap(SSyncRaftProgressMap* progressMap, visitProgressFp
   }
 }
 
+static void copyProgress(SSyncRaftProgress* progress, void* arg) {
+  assert(progress->refCount > 0);
+  SSyncRaftProgressMap* to = (SSyncRaftProgressMap*)arg;
+  syncRaftAddToProgressMap(to, progress);
+}
+
+static void refProgress(SSyncRaftProgress* progress) {
+  progress->refCount += 1;
+}
+
+static void unrefProgress(SSyncRaftProgress* progress, void* arg) {
+  (void)arg;
+  progress->refCount -= 1;
+  assert(progress->refCount >= 0);
+  if (progress->refCount == 0) {
+    free(progress);
+  }
+}
+ 
 /**
  * ResetState moves the Progress into the specified State, resetting ProbeSent,
  * PendingSnapshot, and Inflights.

source/libs/sync/src/sync_raft_progress_tracker.c

@@ -22,13 +22,26 @@ SSyncRaftProgressTracker* syncRaftOpenProgressTracker(SSyncRaft* pRaft) {
     return NULL;
   }
 
-  syncRaftInitNodeMap(&tracker->config.learners);
+  syncRaftInitTrackConfig(&tracker->config);
   syncRaftInitNodeMap(&tracker->config.learnersNext);
   tracker->pRaft = pRaft;
 
   return tracker;
 }
 
+void syncRaftInitTrackConfig(SSyncRaftProgressTrackerConfig* config) {
+  syncRaftInitNodeMap(&config->learners);
+  syncRaftInitNodeMap(&config->learnersNext);
+  syncRaftInitQuorumJointConfig(&config->voters);
+  config->autoLeave = false;
+}
+
+void syncRaftFreeTrackConfig(SSyncRaftProgressTrackerConfig* config) {
+  syncRaftFreeNodeMap(&config->learners);
+  syncRaftFreeNodeMap(&config->learnersNext);
+  syncRaftFreeQuorumJointConfig(&config->voters);
+}
+
 void syncRaftResetVotes(SSyncRaftProgressTracker* tracker) {
   taosHashClear(tracker->votesMap);
 }
@@ -47,21 +60,21 @@ void syncRaftRecordVote(SSyncRaftProgressTracker* tracker, SyncNodeId id, bool g
   taosHashPut(tracker->votesMap, &id, sizeof(SyncNodeId), &type, sizeof(ESyncRaftVoteType*));
 }
 
-void syncRaftCloneTrackerConfig(const SSyncRaftProgressTrackerConfig* from, SSyncRaftProgressTrackerConfig* to) {
+void syncRaftCopyTrackerConfig(const SSyncRaftProgressTrackerConfig* from, SSyncRaftProgressTrackerConfig* to) {
   memcpy(to, from, sizeof(SSyncRaftProgressTrackerConfig));
 }
 
-int syncRaftCheckProgress(const SSyncRaftProgressTrackerConfig* config, SSyncRaftProgressMap* progressMap) {
+int syncRaftCheckTrackerConfigInProgress(SSyncRaftProgressTrackerConfig* config, SSyncRaftProgressMap* progressMap) {
 	// NB: intentionally allow the empty config. In production we'll never see a
 	// non-empty config (we prevent it from being created) but we will need to
 	// be able to *create* an initial config, for example during bootstrap (or
 	// during tests). Instead of having to hand-code this, we allow
 	// transitioning from an empty config into any other legal and non-empty
 	// config.  
-  if (!syncRaftIsAllInProgressMap(&config->voters.incoming, progressMap)) return -1;
-  if (!syncRaftIsAllInProgressMap(&config->voters.outgoing, progressMap)) return -1;
-  if (!syncRaftIsAllInProgressMap(&config->learners, progressMap)) return -1;
-  if (!syncRaftIsAllInProgressMap(&config->learnersNext, progressMap)) return -1;
+  if (!syncRaftIsAllNodeInProgressMap(&config->voters.incoming, progressMap)) return -1;
+  if (!syncRaftIsAllNodeInProgressMap(&config->voters.outgoing, progressMap)) return -1;
+  if (!syncRaftIsAllNodeInProgressMap(&config->learners, progressMap)) return -1;
+  if (!syncRaftIsAllNodeInProgressMap(&config->learnersNext, progressMap)) return -1;
   return 0;
 }
 

source/libs/sync/src/sync_raft_quorum_joint.c

@@ -41,6 +41,16 @@ ESyncRaftVoteType syncRaftVoteResult(SSyncRaftQuorumJointConfig* config, SHashOb
   return SYNC_RAFT_VOTE_PENDING;
 }
 
+void syncRaftInitQuorumJointConfig(SSyncRaftQuorumJointConfig* config) {
+  syncRaftInitNodeMap(&config->incoming);
+  syncRaftInitNodeMap(&config->outgoing);
+}
+
+void syncRaftFreeQuorumJointConfig(SSyncRaftQuorumJointConfig* config) {
+  syncRaftFreeNodeMap(&config->incoming);
+  syncRaftFreeNodeMap(&config->outgoing);
+}
+
 void syncRaftJointConfigAddToIncoming(SSyncRaftQuorumJointConfig* config, SyncNodeId id) {
   syncRaftAddToNodeMap(&config->incoming, id);
 }

source/libs/sync/src/sync_raft_restore.c

@@ -28,21 +28,26 @@ static int toConfChangeSingle(const SSyncConfigState* cs, SSyncConfChangeSingleA
 // the Changer only needs a ProgressMap (not a whole Tracker) at which point
 // this can just take LastIndex and MaxInflight directly instead and cook up
 // the results from that alone.
-int syncRaftRestoreConfig(SSyncRaftChanger* changer, const SSyncConfigState* cs) {
+int syncRaftRestoreConfig(SSyncRaftChanger* changer, const SSyncConfigState* cs,
+                          SSyncRaftProgressTrackerConfig* config, SSyncRaftProgressMap* progressMap) {
   SSyncConfChangeSingleArray outgoing;
   SSyncConfChangeSingleArray incoming;
   SSyncConfChangeSingleArray css;
   SSyncRaftProgressTracker* tracker = changer->tracker;
-  SSyncRaftProgressTrackerConfig* config = &tracker->config;
-  SSyncRaftProgressMap* progressMap = &tracker->progressMap;
   int i, ret;
 
+  syncRaftInitConfArray(&outgoing);
+  syncRaftInitConfArray(&incoming);
+
+  syncRaftInitTrackConfig(config);
+  syncRaftInitProgressMap(progressMap);
+  
   ret = toConfChangeSingle(cs, &outgoing, &incoming);
   if (ret != 0) {
     goto out;
   }
 
-  if (outgoing.n == 0) {
+  if (syncRaftConfArrayIsEmpty(&outgoing)) {
     // No outgoing config, so just apply the incoming changes one by one.
     for (i = 0; i < incoming.n; ++i) {
       css = (SSyncConfChangeSingleArray) {
@@ -53,6 +58,9 @@ int syncRaftRestoreConfig(SSyncRaftChanger* changer, const SSyncConfigState* cs)
       if (ret != 0) {
         goto out;
       }
+
+      syncRaftCopyTrackerConfig(config, &changer->tracker->config);
+      syncRaftCopyProgressMap(progressMap, &changer->tracker->progressMap);
     }
   } else {
 		// The ConfState describes a joint configuration.
@@ -69,6 +77,8 @@ int syncRaftRestoreConfig(SSyncRaftChanger* changer, const SSyncConfigState* cs)
       if (ret != 0) {
         goto out;
       }
+      syncRaftCopyTrackerConfig(config, &changer->tracker->config);
+      syncRaftCopyProgressMap(progressMap, &changer->tracker->progressMap);
     }
 
     ret = syncRaftChangerEnterJoint(changer, cs->autoLeave, &incoming, config, progressMap);
@@ -78,8 +88,9 @@ int syncRaftRestoreConfig(SSyncRaftChanger* changer, const SSyncConfigState* cs)
   }
 
 out:
-  if (incoming.n != 0) free(incoming.changes);
-  if (outgoing.n != 0) free(outgoing.changes);
+  syncRaftFreeConfArray(&incoming);
+  syncRaftFreeConfArray(&outgoing);
+
   return ret;
 }
 
@@ -102,8 +113,6 @@ static void addToConfChangeSingleArray(SSyncConfChangeSingleArray* out, int* i,
 static int toConfChangeSingle(const SSyncConfigState* cs, SSyncConfChangeSingleArray* out, SSyncConfChangeSingleArray* in) {
   int i;
 
-  out->n = in->n = 0;
-
   out->n = syncRaftNodeMapSize(&cs->votersOutgoing);
   out->changes = (SSyncConfChangeSingle*)malloc(sizeof(SSyncConfChangeSingle) * out->n);
   if (out->changes == NULL) {