Hadoop2.6.0学习笔记（十四）Hadoop Two HA: ActiveStandbyElector
synchronized void processWatchEvent(ZooKeeper zk, WatchedEvent event) {Event.EventType eventType = event.getType();
if (isStaleClient(zk)) return;
if (eventType == Event.EventType.None) {
// the connection state has changed
switch (event.getState()) {
case SyncConnected:
LOG.info("Session connected.");
// if the listener was asked to move to safe state then it needs tobe undone
ConnectionState prevConnectionState = zkConnectionState;
zkConnectionState = ConnectionState.CONNECTED;
if (prevConnectionState == ConnectionState.DISCONNECTED && wantToBeInElection) {
monitorActiveStatus();
}
break;
case Disconnected:
LOG.info("Session disconnected. Entering neutral mode...");
// ask the app to move to safe state because zookeeper connection
// is not active and we dont know our state
zkConnectionState = ConnectionState.DISCONNECTED;
enterNeutralMode();
break;
case Expired:
// the connection got terminated because of session timeout
// call listener to reconnect
LOG.info("Session expired. Entering neutral mode and rejoining...");
enterNeutralMode();
reJoinElection(0);
break;
case SaslAuthenticated:
LOG.info("Successfully authenticated to ZooKeeper using SASL.");
break;
default:
fatalError("Unexpected Zookeeper watch event state: " + event.getState());
break;
}
return;
}
// 另一方面，对于node的变更事件，ActiveStandbyElector也会执行相应的动作。
String path = event.getPath();
if (path != null) {
switch (eventType) {
case NodeDeleted:
if (state == State.ACTIVE) {
enterNeutralMode();
}
joinElectionInternal();
break;
case NodeDataChanged:
monitorActiveStatus();
break;
default:
LOG.debug("Unexpected node event: " + eventType + " for path: " + path);
monitorActiveStatus();
}
return;
}
// some unexpected error has occurred
fatalError("Unexpected watch error from Zookeeper");
}
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