2 * Copyright (c) 2015 Cisco Systems, Inc. and others. All rights reserved.
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6 * and is available at http://www.eclipse.org/legal/epl-v10.html
9 package org.opendaylight.controller.cluster.raft.behaviors;
11 import akka.actor.ActorRef;
12 import com.google.common.base.Preconditions;
13 import org.opendaylight.controller.cluster.raft.base.messages.FollowerInitialSyncUpStatus;
14 import org.slf4j.Logger;
15 import org.slf4j.LoggerFactory;
18 * The SyncStatusTracker tracks if a Follower is in sync with any given Leader or not
19 * When an update is received from the Leader and the update happens to be the first update
20 * from that Leader then the SyncStatusTracker will not mark the Follower as not in-sync till the
21 * Followers commitIndex matches the commitIndex that the Leader sent in it's very first update.
22 * Subsequently when an update is received the tracker will consider the Follower to be out of
23 * sync if it is behind by 'syncThreshold' commits.
25 public class SyncStatusTracker {
26 private static final Logger LOG = LoggerFactory.getLogger(SyncStatusTracker.class);
28 private static final boolean IN_SYNC = true;
29 private static final boolean NOT_IN_SYNC = false;
31 private final String id;
32 private final ActorRef actor;
33 private final int syncThreshold;
35 // FIXME: what is this magic constant?
36 private long minimumExpectedIndex = -2L;
37 private String syncedLeaderId = null;
38 private boolean syncStatus = false;
40 public SyncStatusTracker(final ActorRef actor, final String id, final int syncThreshold) {
41 this.actor = Preconditions.checkNotNull(actor, "actor should not be null");
42 this.id = Preconditions.checkNotNull(id, "id should not be null");
43 Preconditions.checkArgument(syncThreshold >= 0, "syncThreshold should be greater than or equal to 0");
44 this.syncThreshold = syncThreshold;
47 public void update(final String leaderId, final long leaderCommit, final long commitIndex) {
48 Preconditions.checkNotNull(leaderId, "leaderId should not be null");
50 if (!leaderId.equals(syncedLeaderId)) {
51 minimumExpectedIndex = leaderCommit;
52 LOG.debug("Last sync leader {} does not match current leader {}, need to catch up to {}", syncedLeaderId,
53 leaderId, leaderCommit);
54 changeSyncStatus(NOT_IN_SYNC, true);
55 syncedLeaderId = leaderId;
59 final long lag = leaderCommit - commitIndex;
60 if (lag > syncThreshold) {
61 LOG.debug("Lagging {} entries behind leader {}", lag, leaderId);
62 changeSyncStatus(NOT_IN_SYNC, false);
63 } else if (commitIndex >= minimumExpectedIndex) {
64 LOG.debug("Lagging {} entries behind leader and reached {} (of expected {})", lag, leaderId, commitIndex,
65 minimumExpectedIndex);
66 changeSyncStatus(IN_SYNC, false);
70 private void changeSyncStatus(final boolean newSyncStatus, final boolean forceStatusChange) {
71 if (forceStatusChange || newSyncStatus != syncStatus) {
72 actor.tell(new FollowerInitialSyncUpStatus(newSyncStatus, id), ActorRef.noSender());
73 syncStatus = newSyncStatus;
75 LOG.trace("No change in sync status of {}, dampening message", actor);