From: Tom Pantelis Date: Fri, 16 Jun 2017 14:51:19 +0000 (-0400) Subject: Refactor Follower#handleAppendEntries X-Git-Tag: release/nitrogen~50 X-Git-Url: https://git.opendaylight.org/gerrit/gitweb?p=controller.git;a=commitdiff_plain;h=fefb98e65db3684161b707dde5b3f48f6072358a Refactor Follower#handleAppendEntries This method is large - refactor it a bit. Change-Id: Idae1883accdd7c73b57471501e66398306cf6e91 Signed-off-by: Tom Pantelis --- diff --git a/opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/behaviors/Follower.java b/opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/behaviors/Follower.java index 11fa23748e..e1f440dace 100644 --- a/opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/behaviors/Follower.java +++ b/opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/behaviors/Follower.java @@ -132,7 +132,6 @@ public class Follower extends AbstractRaftActorBehavior { @Override protected RaftActorBehavior handleAppendEntries(final ActorRef sender, final AppendEntries appendEntries) { - int numLogEntries = appendEntries.getEntries().size(); if (log.isTraceEnabled()) { log.trace("{}: handleAppendEntries: {}", logName(), appendEntries); @@ -140,10 +139,6 @@ public class Follower extends AbstractRaftActorBehavior { log.debug("{}: handleAppendEntries: {}", logName(), appendEntries); } - // TODO : Refactor this method into a bunch of smaller methods - // to make it easier to read. Before refactoring ensure tests - // cover the code properly - if (snapshotTracker != null && !snapshotTracker.getLeaderId().equals(appendEntries.getLeaderId())) { log.debug("{}: snapshot install is in progress but the prior snapshot leaderId {} does not match the " + "AppendEntries leaderId {}", logName(), snapshotTracker.getLeaderId(), appendEntries.getLeaderId()); @@ -166,123 +161,20 @@ public class Follower extends AbstractRaftActorBehavior { leaderPayloadVersion = appendEntries.getPayloadVersion(); // First check if the logs are in sync or not - long lastIndex = lastIndex(); - - if (isOutOfSync(appendEntries)) { - // We found that the log was out of sync so just send a negative - // reply and return - - final AppendEntriesReply reply = new AppendEntriesReply(context.getId(), currentTerm(), false, lastIndex, - lastTerm(), context.getPayloadVersion()); - - log.info("{}: Follower is out-of-sync so sending negative reply: {}", logName(), reply); + if (isOutOfSync(appendEntries, sender)) { updateInitialSyncStatus(appendEntries.getLeaderCommit(), appendEntries.getLeaderId()); - sender.tell(reply, actor()); return this; } - if (numLogEntries > 0) { - log.debug("{}: Number of entries to be appended = {}", logName(), numLogEntries); - - // 3. If an existing entry conflicts with a new one (same index - // but different terms), delete the existing entry and all that - // follow it (§5.3) - int addEntriesFrom = 0; - if (context.getReplicatedLog().size() > 0) { - - // Find the entry up until the one that is not in the follower's log - for (int i = 0;i < numLogEntries; i++, addEntriesFrom++) { - ReplicatedLogEntry matchEntry = appendEntries.getEntries().get(i); - - if (!isLogEntryPresent(matchEntry.getIndex())) { - // newEntry not found in the log - break; - } - - long existingEntryTerm = getLogEntryTerm(matchEntry.getIndex()); - - log.debug("{}: matchEntry {} is present: existingEntryTerm: {}", logName(), matchEntry, - existingEntryTerm); - - // existingEntryTerm == -1 means it's in the snapshot and not in the log. We don't know - // what the term was so we'll assume it matches. - if (existingEntryTerm == -1 || existingEntryTerm == matchEntry.getTerm()) { - continue; - } - - if (!context.getRaftPolicy().applyModificationToStateBeforeConsensus()) { - - log.info("{}: Removing entries from log starting at {}", logName(), matchEntry.getIndex()); - - // Entries do not match so remove all subsequent entries - if (!context.getReplicatedLog().removeFromAndPersist(matchEntry.getIndex())) { - // Could not remove the entries - this means the matchEntry index must be in the - // snapshot and not the log. In this case the prior entries are part of the state - // so we must send back a reply to force a snapshot to completely re-sync the - // follower's log and state. - - log.info("{}: Could not remove entries - sending reply to force snapshot", logName()); - updateInitialSyncStatus(appendEntries.getLeaderCommit(), appendEntries.getLeaderId()); - sender.tell(new AppendEntriesReply(context.getId(), currentTerm(), false, lastIndex, - lastTerm(), context.getPayloadVersion(), true), actor()); - return this; - } - - break; - } else { - updateInitialSyncStatus(appendEntries.getLeaderCommit(), appendEntries.getLeaderId()); - sender.tell(new AppendEntriesReply(context.getId(), currentTerm(), false, lastIndex, - lastTerm(), context.getPayloadVersion(), true), actor()); - return this; - } - } - } - - lastIndex = lastIndex(); - log.debug("{}: After cleanup, lastIndex: {}, entries to be added from: {}", logName(), - lastIndex, addEntriesFrom); - - // When persistence successfully completes for each new log entry appended, we need to determine if we - // should capture a snapshot to compact the persisted log. shouldCaptureSnapshot tracks whether or not - // one of the log entries has exceeded the log size threshold whereby a snapshot should be taken. However - // we don't initiate the snapshot at that log entry but rather after the last log entry has been persisted. - // This is done because subsequent log entries after the one that tripped the threshold may have been - // applied to the state already, as the persistence callback occurs async, and we want those entries - // purged from the persisted log as well. - final AtomicBoolean shouldCaptureSnapshot = new AtomicBoolean(false); - final Procedure appendAndPersistCallback = logEntry -> { - final List entries = appendEntries.getEntries(); - final ReplicatedLogEntry lastEntryToAppend = entries.get(entries.size() - 1); - if (shouldCaptureSnapshot.get() && logEntry == lastEntryToAppend) { - context.getSnapshotManager().capture(context.getReplicatedLog().last(), getReplicatedToAllIndex()); - } - }; - - // 4. Append any new entries not already in the log - for (int i = addEntriesFrom; i < numLogEntries; i++) { - ReplicatedLogEntry entry = appendEntries.getEntries().get(i); - - log.debug("{}: Append entry to log {}", logName(), entry.getData()); - - context.getReplicatedLog().appendAndPersist(entry, appendAndPersistCallback, false); - - shouldCaptureSnapshot.compareAndSet(false, - context.getReplicatedLog().shouldCaptureSnapshot(entry.getIndex())); - - if (entry.getData() instanceof ServerConfigurationPayload) { - context.updatePeerIds((ServerConfigurationPayload)entry.getData()); - } - } - - log.debug("{}: Log size is now {}", logName(), context.getReplicatedLog().size()); + if (!processNewEntries(appendEntries, sender)) { + updateInitialSyncStatus(appendEntries.getLeaderCommit(), appendEntries.getLeaderId()); + return this; } - // 5. If leaderCommit > commitIndex, set commitIndex = - // min(leaderCommit, index of last new entry) - - lastIndex = lastIndex(); + long lastIndex = lastIndex(); long prevCommitIndex = context.getCommitIndex(); + // If leaderCommit > commitIndex, set commitIndex = min(leaderCommit, index of last new entry) if (appendEntries.getLeaderCommit() > prevCommitIndex) { context.setCommitIndex(Math.min(appendEntries.getLeaderCommit(), lastIndex)); } @@ -301,14 +193,13 @@ public class Follower extends AbstractRaftActorBehavior { } // Reply to the leader before applying any previous state so as not to hold up leader consensus. - updateInitialSyncStatus(appendEntries.getLeaderCommit(), appendEntries.getLeaderId()); sender.tell(reply, actor()); - // If commitIndex > lastApplied: increment lastApplied, apply - // log[lastApplied] to state machine (§5.3) - // check if there are any entries to be applied. last-applied can be equal to last-index - if (appendEntries.getLeaderCommit() > context.getLastApplied() - && context.getLastApplied() < lastIndex) { + updateInitialSyncStatus(appendEntries.getLeaderCommit(), appendEntries.getLeaderId()); + + // If leaderCommit > lastApplied, increment lastApplied and apply log[lastApplied] to state machine (§5.3). + // lastApplied can be equal to lastIndex. + if (appendEntries.getLeaderCommit() > context.getLastApplied() && context.getLastApplied() < lastIndex) { if (log.isDebugEnabled()) { log.debug("{}: applyLogToStateMachine, appendEntries.getLeaderCommit(): {}, " + "context.getLastApplied(): {}, lastIndex(): {}", logName(), @@ -327,7 +218,107 @@ public class Follower extends AbstractRaftActorBehavior { return this; } - private boolean isOutOfSync(final AppendEntries appendEntries) { + private boolean processNewEntries(final AppendEntries appendEntries, final ActorRef sender) { + int numLogEntries = appendEntries.getEntries().size(); + if (numLogEntries == 0) { + return true; + } + + log.debug("{}: Number of entries to be appended = {}", logName(), numLogEntries); + + long lastIndex = lastIndex(); + int addEntriesFrom = 0; + + // First check for conflicting entries. If an existing entry conflicts with a new one (same index but different + // term), delete the existing entry and all that follow it (§5.3) + if (context.getReplicatedLog().size() > 0) { + // Find the entry up until the one that is not in the follower's log + for (int i = 0;i < numLogEntries; i++, addEntriesFrom++) { + ReplicatedLogEntry matchEntry = appendEntries.getEntries().get(i); + + if (!isLogEntryPresent(matchEntry.getIndex())) { + // newEntry not found in the log + break; + } + + long existingEntryTerm = getLogEntryTerm(matchEntry.getIndex()); + + log.debug("{}: matchEntry {} is present: existingEntryTerm: {}", logName(), matchEntry, + existingEntryTerm); + + // existingEntryTerm == -1 means it's in the snapshot and not in the log. We don't know + // what the term was so we'll assume it matches. + if (existingEntryTerm == -1 || existingEntryTerm == matchEntry.getTerm()) { + continue; + } + + if (!context.getRaftPolicy().applyModificationToStateBeforeConsensus()) { + log.info("{}: Removing entries from log starting at {}", logName(), matchEntry.getIndex()); + + // Entries do not match so remove all subsequent entries + if (!context.getReplicatedLog().removeFromAndPersist(matchEntry.getIndex())) { + // Could not remove the entries - this means the matchEntry index must be in the + // snapshot and not the log. In this case the prior entries are part of the state + // so we must send back a reply to force a snapshot to completely re-sync the + // follower's log and state. + + log.info("{}: Could not remove entries - sending reply to force snapshot", logName()); + sender.tell(new AppendEntriesReply(context.getId(), currentTerm(), false, lastIndex, + lastTerm(), context.getPayloadVersion(), true), actor()); + return false; + } + + break; + } else { + sender.tell(new AppendEntriesReply(context.getId(), currentTerm(), false, lastIndex, + lastTerm(), context.getPayloadVersion(), true), actor()); + return false; + } + } + } + + lastIndex = lastIndex(); + log.debug("{}: After cleanup, lastIndex: {}, entries to be added from: {}", logName(), lastIndex, + addEntriesFrom); + + // When persistence successfully completes for each new log entry appended, we need to determine if we + // should capture a snapshot to compact the persisted log. shouldCaptureSnapshot tracks whether or not + // one of the log entries has exceeded the log size threshold whereby a snapshot should be taken. However + // we don't initiate the snapshot at that log entry but rather after the last log entry has been persisted. + // This is done because subsequent log entries after the one that tripped the threshold may have been + // applied to the state already, as the persistence callback occurs async, and we want those entries + // purged from the persisted log as well. + final AtomicBoolean shouldCaptureSnapshot = new AtomicBoolean(false); + final Procedure appendAndPersistCallback = logEntry -> { + final List entries = appendEntries.getEntries(); + final ReplicatedLogEntry lastEntryToAppend = entries.get(entries.size() - 1); + if (shouldCaptureSnapshot.get() && logEntry == lastEntryToAppend) { + context.getSnapshotManager().capture(context.getReplicatedLog().last(), getReplicatedToAllIndex()); + } + }; + + // Append any new entries not already in the log + for (int i = addEntriesFrom; i < numLogEntries; i++) { + ReplicatedLogEntry entry = appendEntries.getEntries().get(i); + + log.debug("{}: Append entry to log {}", logName(), entry.getData()); + + context.getReplicatedLog().appendAndPersist(entry, appendAndPersistCallback, false); + + shouldCaptureSnapshot.compareAndSet(false, + context.getReplicatedLog().shouldCaptureSnapshot(entry.getIndex())); + + if (entry.getData() instanceof ServerConfigurationPayload) { + context.updatePeerIds((ServerConfigurationPayload)entry.getData()); + } + } + + log.debug("{}: Log size is now {}", logName(), context.getReplicatedLog().size()); + + return true; + } + + private boolean isOutOfSync(final AppendEntries appendEntries, final ActorRef sender) { final long lastIndex = lastIndex(); if (lastIndex == -1 && appendEntries.getPrevLogIndex() != -1) { @@ -337,6 +328,8 @@ public class Follower extends AbstractRaftActorBehavior { log.info("{}: The followers log is empty and the senders prevLogIndex is {}", logName(), appendEntries.getPrevLogIndex()); + + sendOutOfSyncAppendEntriesReply(sender, false); return true; } @@ -352,6 +345,8 @@ public class Follower extends AbstractRaftActorBehavior { + "entries prevLogTerm {} - lastIndex: {}, snapshotIndex: {}", logName(), appendEntries.getPrevLogIndex(), prevLogTerm, appendEntries.getPrevLogTerm(), lastIndex, context.getReplicatedLog().getSnapshotIndex()); + + sendOutOfSyncAppendEntriesReply(sender, false); return true; } } else if (appendEntries.getPrevLogIndex() != -1) { @@ -361,6 +356,8 @@ public class Follower extends AbstractRaftActorBehavior { log.info("{}: The log is not empty but the prevLogIndex {} was not found in it - lastIndex: {}, " + "snapshotIndex: {}", logName(), appendEntries.getPrevLogIndex(), lastIndex, context.getReplicatedLog().getSnapshotIndex()); + + sendOutOfSyncAppendEntriesReply(sender, false); return true; } } @@ -373,6 +370,8 @@ public class Follower extends AbstractRaftActorBehavior { log.info("{}: Cannot append entries because the replicatedToAllIndex {} does not appear to be in the " + "in-memory journal", logName(), appendEntries.getReplicatedToAllIndex()); + + sendOutOfSyncAppendEntriesReply(sender, false); return true; } @@ -380,6 +379,8 @@ public class Follower extends AbstractRaftActorBehavior { if (entries.size() > 0 && !isLogEntryPresent(entries.get(0).getIndex() - 1)) { log.info("{}: Cannot append entries because the calculated previousIndex {} was not found in the " + "in-memory journal", logName(), entries.get(0).getIndex() - 1); + + sendOutOfSyncAppendEntriesReply(sender, false); return true; } } @@ -387,6 +388,15 @@ public class Follower extends AbstractRaftActorBehavior { return false; } + private void sendOutOfSyncAppendEntriesReply(final ActorRef sender, boolean forceInstallSnapshot) { + // We found that the log was out of sync so just send a negative reply. + final AppendEntriesReply reply = new AppendEntriesReply(context.getId(), currentTerm(), false, lastIndex(), + lastTerm(), context.getPayloadVersion(), forceInstallSnapshot); + + log.info("{}: Follower is out-of-sync so sending negative reply: {}", logName(), reply); + sender.tell(reply, actor()); + } + @Override protected RaftActorBehavior handleAppendEntriesReply(final ActorRef sender, final AppendEntriesReply appendEntriesReply) {