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 class LeaderInfo {
27 final long minimumCommitIndex;
28 final String leaderId;
30 LeaderInfo(final String leaderId, final long minimumCommitIndex) {
31 this.leaderId = Preconditions.checkNotNull(leaderId);
32 this.minimumCommitIndex = minimumCommitIndex;
36 private static final Logger LOG = LoggerFactory.getLogger(SyncStatusTracker.class);
38 private static final boolean IN_SYNC = true;
39 private static final boolean NOT_IN_SYNC = false;
41 private final long syncThreshold;
42 private final ActorRef actor;
43 private final String id;
45 private LeaderInfo syncTarget;
46 private boolean syncStatus;
48 public SyncStatusTracker(final ActorRef actor, final String id, final long syncThreshold) {
49 this.actor = Preconditions.checkNotNull(actor, "actor should not be null");
50 this.id = Preconditions.checkNotNull(id, "id should not be null");
51 Preconditions.checkArgument(syncThreshold >= 0, "syncThreshold should be greater than or equal to 0");
52 this.syncThreshold = syncThreshold;
55 public void update(final String leaderId, final long leaderCommit, final long commitIndex) {
56 Preconditions.checkNotNull(leaderId, "leaderId should not be null");
58 if (syncTarget == null || !leaderId.equals(syncTarget.leaderId)) {
59 LOG.debug("{}: Last sync leader does not match current leader {}, need to catch up to {}", id,
60 leaderId, leaderCommit);
61 changeSyncStatus(NOT_IN_SYNC, true);
62 syncTarget = new LeaderInfo(leaderId, leaderCommit);
66 final long lag = leaderCommit - commitIndex;
67 if (lag > syncThreshold) {
68 LOG.debug("{}: Lagging {} entries behind leader {}", id, lag, leaderId);
69 changeSyncStatus(NOT_IN_SYNC, false);
70 } else if (commitIndex >= syncTarget.minimumCommitIndex) {
71 LOG.debug("{}: Lagging {} entries behind leader {} and reached {} (of expected {})", id, lag, leaderId,
72 commitIndex, syncTarget.minimumCommitIndex);
73 changeSyncStatus(IN_SYNC, false);
77 private void changeSyncStatus(final boolean newSyncStatus, final boolean forceStatusChange) {
78 if (forceStatusChange || newSyncStatus != syncStatus) {
79 actor.tell(new FollowerInitialSyncUpStatus(newSyncStatus, id), ActorRef.noSender());
80 syncStatus = newSyncStatus;
82 LOG.trace("{}: No change in sync status of, dampening message", id);