private void checkLeadership(List<String> children) throws Exception {
final String localOurPath = ourPath.get();
List<String> sortedChildren = LockInternals.getSortedChildren(LOCK_NAME, sorter, children);
int ourIndex =
(localOurPath != null) ? sortedChildren.indexOf(ZKPaths.getNodeFromPath(localOurPath)) : -1;
if (ourIndex < 0) {
log.error("Can't find our node. Resetting. Index: " + ourIndex);
reset();
} else if (ourIndex == 0) {
setLeadership(true);
} else {
String watchPath = sortedChildren.get(ourIndex - 1);
Watcher watcher =
new Watcher() {
@Override
public void process(WatchedEvent event) {
if ((state.get() == State.STARTED)
&& (event.getType() == Event.EventType.NodeDeleted)
&& (localOurPath != null)) {
try {
getChildren();
} catch (Exception ex) {
log.error("An error occurred checking the leadership.", ex);
}
}
}
};
BackgroundCallback callback =
new BackgroundCallback() {
@Override
public void processResult(CuratorFramework client, CuratorEvent event)
throws Exception {
if (event.getResultCode() == KeeperException.Code.NONODE.intValue()) {
// previous node is gone - reset
reset();
}
}
};
client
.checkExists()
.usingWatcher(watcher)
.inBackground(callback)
.forPath(ZKPaths.makePath(latchPath, watchPath));
}
}
private void checkForLeadership() throws Exception {
List<String> sortedChildren =
LockInternals.getSortedChildren(client, latchPath, LOCK_NAME, sorter);
if (sortedChildren.size() == 0) {
throw new Exception("no children - unexpected state");
}
int ourIndex = sortedChildren.indexOf(ZKPaths.getNodeFromPath(ourPath));
if (ourIndex == 0) {
setLeadership(true);
} else {
final String ourPathWhenWatched =
ourPath; // protected against a lost/suspended connection and an old watcher - I'm not
// sure if this is possible but it can't hurt
String watchPath = sortedChildren.get(ourIndex - 1);
Watcher watcher =
new Watcher() {
@Override
public void process(WatchedEvent event) {
if ((event.getType() == Event.EventType.NodeDeleted)
&& (ourPath != null)
&& ourPath.equals(ourPathWhenWatched)) {
try {
checkForLeadership();
} catch (Exception ex) {
log.error("An error ocurred checking the leadership.", ex);
}
}
}
};
if (client.checkExists().usingWatcher(watcher).forPath(ZKPaths.makePath(latchPath, watchPath))
== null) {
// the previous Participant may be down, so we need to reevaluate the list
// to get the actual previous Participant or get the leadership
checkForLeadership();
}
}
}
/**
* Return the id for the current leader. If for some reason there is no current leader, a dummy
* participant is returned.
*
* <p><B>NOTE</B> - this method polls the ZK server. Therefore it can possibly return a value that
* does not match {@link #hasLeadership()} as hasLeadership uses a local field of the class.
*
* @return leader
* @throws Exception ZK errors, interruptions, etc.
*/
public Participant getLeader() throws Exception {
Collection<String> participantNodes =
LockInternals.getParticipantNodes(client, latchPath, LOCK_NAME, sorter);
return LeaderSelector.getLeader(client, participantNodes);
}
