BUG 2185 : Follower should request forceInstallSnapshot in out-of-sync scenario

[controller.git] / opendaylight / md-sal / sal-akka-raft / src / main / java / org / opendaylight / controller / cluster / raft / behaviors / AbstractLeader.java

diff --git a/opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/behaviors/AbstractLeader.java b/opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/behaviors/AbstractLeader.java
index 85f2f153ab3046d6541225c95d3863be3435b6b0..578989599752f41c0fefd635c879effbc187c357 100644 (file)
--- a/opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/behaviors/AbstractLeader.java
+++ b/opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/behaviors/AbstractLeader.java
@@ -196,7 +196,15 @@ public abstract class AbstractLeader extends AbstractRaftActorBehavior {
 
             long followerLastLogIndex = appendEntriesReply.getLogLastIndex();
             ReplicatedLogEntry followersLastLogEntry = context.getReplicatedLog().get(followerLastLogIndex);
-            if(followerLastLogIndex < 0 || (followersLastLogEntry != null &&
+            if(appendEntriesReply.isForceInstallSnapshot()) {
+                // Reset the followers match and next index. This is to signal that this follower has nothing
+                // in common with this Leader and so would require a snapshot to be installed
+                followerLogInformation.setMatchIndex(-1);
+                followerLogInformation.setNextIndex(-1);
+
+                // Force initiate a snapshot capture
+                initiateCaptureSnapshot(followerId);
+            } else if(followerLastLogIndex < 0 || (followersLastLogEntry != null &&
                     followersLastLogEntry.getTerm() == appendEntriesReply.getLogLastTerm())) {
                 // The follower's log is empty or the last entry is present in the leader's journal
                 // and the terms match so the follower is just behind the leader's journal from
@@ -539,7 +547,9 @@ public abstract class AbstractLeader extends AbstractRaftActorBehavior {
 
                     // Send heartbeat to follower whenever install snapshot is initiated.
                     sendAppendEntries = true;
-                    initiateCaptureSnapshot(followerId, followerNextIndex);
+                    if (canInstallSnapshot(followerNextIndex)) {
+                        initiateCaptureSnapshot(followerId);
+                    }
 
                 } else if(sendHeartbeat) {
                     // we send an AppendEntries, even if the follower is inactive
@@ -583,27 +593,32 @@ public abstract class AbstractLeader extends AbstractRaftActorBehavior {
      * 6. If another follower requires a snapshot and a snapshot has been collected (via CaptureSnapshotReply)
      * then send the existing snapshot in chunks to the follower.
      * @param followerId
-     * @param followerNextIndex
      */
-    private void initiateCaptureSnapshot(String followerId, long followerNextIndex) {
-        if (!context.getReplicatedLog().isPresent(followerNextIndex) &&
-                context.getReplicatedLog().isInSnapshot(followerNextIndex)) {
-
-            if (snapshot.isPresent()) {
-                // if a snapshot is present in the memory, most likely another install is in progress
-                // no need to capture snapshot.
-                // This could happen if another follower needs an install when one is going on.
-                final ActorSelection followerActor = context.getPeerActorSelection(followerId);
-                sendSnapshotChunk(followerActor, followerId);
+    private void initiateCaptureSnapshot(String followerId) {
+        if (snapshot.isPresent()) {
+            // if a snapshot is present in the memory, most likely another install is in progress
+            // no need to capture snapshot.
+            // This could happen if another follower needs an install when one is going on.
+            final ActorSelection followerActor = context.getPeerActorSelection(followerId);
+            sendSnapshotChunk(followerActor, followerId);
 
 
-            } else {
-                context.getSnapshotManager().captureToInstall(context.getReplicatedLog().last(),
-                        this.getReplicatedToAllIndex(), followerId);
-            }
+        } else {
+            context.getSnapshotManager().captureToInstall(context.getReplicatedLog().last(),
+                    this.getReplicatedToAllIndex(), followerId);
         }
     }
 
+    private boolean canInstallSnapshot(long nextIndex){
+        // If the follower's nextIndex is -1 then we might as well send it a snapshot
+        // Otherwise send it a snapshot only if the nextIndex is not present in the log but is present
+        // in the snapshot
+        return (nextIndex == -1 ||
+                (!context.getReplicatedLog().isPresent(nextIndex)
+                        && context.getReplicatedLog().isInSnapshot(nextIndex)));
+
+    }
+
 
     private void sendInstallSnapshot() {
         LOG.debug("{}: sendInstallSnapshot", logName());
@@ -612,9 +627,7 @@ public abstract class AbstractLeader extends AbstractRaftActorBehavior {
 
             if (followerActor != null) {
                 long nextIndex = e.getValue().getNextIndex();
-
-                if (!context.getReplicatedLog().isPresent(nextIndex) &&
-                    context.getReplicatedLog().isInSnapshot(nextIndex)) {
+                if (canInstallSnapshot(nextIndex)) {
                     sendSnapshotChunk(followerActor, e.getKey());
                 }
             }