Save config file and brocast the PONG when configEpoch changed

This is somehow related with valkey-io#974 and valkey-io#1777. When the epoch changes,
we should save the configuration file and broadcast a PONG as much
as possible.

For example, if a primary down after bumping the epoch, its replicas
may initiate a failover, but the other primaries may refuse to vote
because the epoch of the replica has not been updated.

Or for example, for some reasons we bump the epoch, if the epoch
is not updated in time in the cluster, it may affect the judgment
of message staleness.

Signed-off-by: Binbin <[email protected]>

src/cluster_legacy.c

@@ -1938,7 +1938,7 @@ int clusterBumpConfigEpochWithoutConsensus(void) {
     if (myself->configEpoch == 0 || myself->configEpoch != maxEpoch) {
         server.cluster->currentEpoch++;
         myself->configEpoch = server.cluster->currentEpoch;
-        clusterDoBeforeSleep(CLUSTER_TODO_SAVE_CONFIG | CLUSTER_TODO_FSYNC_CONFIG);
+        clusterDoBeforeSleep(CLUSTER_TODO_SAVE_CONFIG | CLUSTER_TODO_FSYNC_CONFIG | CLUSTER_TODO_BROADCAST_ALL);
         serverLog(LL_NOTICE, "New configEpoch set to %llu", (unsigned long long)myself->configEpoch);
         return C_OK;
     } else {
@@ -2001,7 +2001,7 @@ void clusterHandleConfigEpochCollision(clusterNode *sender) {
     /* Get the next ID available at the best of this node knowledge. */
     server.cluster->currentEpoch++;
     myself->configEpoch = server.cluster->currentEpoch;
-    clusterSaveConfigOrDie(1);
+    clusterDoBeforeSleep(CLUSTER_TODO_SAVE_CONFIG | CLUSTER_TODO_FSYNC_CONFIG | CLUSTER_TODO_BROADCAST_ALL);
     serverLog(LL_NOTICE, "configEpoch collision with node %.40s (%s). configEpoch set to %llu", sender->name,
               sender->human_nodename, (unsigned long long)myself->configEpoch);
 }
@@ -4776,7 +4776,7 @@ void clusterFailoverReplaceYourPrimary(void) {
 
     /* 3) Update state and save config. */
     clusterUpdateState();
-    clusterSaveConfigOrDie(1);
+    clusterDoBeforeSleep(CLUSTER_TODO_SAVE_CONFIG | CLUSTER_TODO_FSYNC_CONFIG);
 
     /* 4) Pong all the other nodes so that they can update the state
      *    accordingly and detect that we switched to primary role. */
@@ -4963,6 +4963,7 @@ void clusterHandleReplicaFailover(void) {
         /* Update my configEpoch to the epoch of the election. */
         if (myself->configEpoch < server.cluster->failover_auth_epoch) {
             myself->configEpoch = server.cluster->failover_auth_epoch;
+            clusterDoBeforeSleep(CLUSTER_TODO_SAVE_CONFIG | CLUSTER_TODO_FSYNC_CONFIG | CLUSTER_TODO_BROADCAST_ALL);
             serverLog(LL_NOTICE, "configEpoch set to %llu after successful failover",
                       (unsigned long long)myself->configEpoch);
         }