String attemptLock(long time, TimeUnit unit, byte[] lockNodeBytes) throws Exception {
final long startMillis = System.currentTimeMillis();
final Long millisToWait = (unit != null) ? unit.toMillis(time) : null;
final byte[] localLockNodeBytes = (revocable.get() != null) ? new byte[0] : lockNodeBytes;
int retryCount = 0;
ensurePath.ensure(client.getZookeeperClient());
String ourPath = null;
boolean hasTheLock = false;
boolean isDone = false;
while (!isDone) {
isDone = true;
try {
if (localLockNodeBytes != null) {
ourPath =
client
.create()
.withProtection()
.withMode(CreateMode.EPHEMERAL_SEQUENTIAL)
.forPath(path, localLockNodeBytes);
} else {
ourPath =
client
.create()
.withProtection()
.withMode(CreateMode.EPHEMERAL_SEQUENTIAL)
.forPath(path);
}
hasTheLock = internalLockLoop(startMillis, millisToWait, ourPath);
} catch (KeeperException.NoNodeException e) {
// gets thrown by StandardLockInternalsDriver when it can't find the lock node
// this can happen when the session expires, etc. So, if the retry allows, just try it all
// again
if (client
.getZookeeperClient()
.getRetryPolicy()
.allowRetry(retryCount++, System.currentTimeMillis() - startMillis)) {
isDone = false;
if (ourPath != null) {
client.delete().inBackground().forPath(ourPath); // just in case
}
} else {
throw e;
}
}
}
if (hasTheLock) {
return ourPath;
}
return null;
}
/**
* Add this instance to the leadership election and attempt to acquire leadership.
*
* @throws Exception errors
*/
public void start() throws Exception {
Preconditions.checkState(state.compareAndSet(State.LATENT, State.STARTED), "Already started");
client.getConnectionStateListenable().addListener(listener);
client.newNamespaceAwareEnsurePath(latchPath).ensure(client.getZookeeperClient());
internalStart();
}
private byte[] get(final String pathSuffix) throws Exception {
return RetryLoop.callWithRetry(
zk.getZookeeperClient(),
new Callable<byte[]>() {
@Override
public byte[] call() throws Exception {
return zk.getData().forPath(buildZookeeperPath(pathSuffix));
}
});
}
private void watch(final String pathSuffix, final Watcher callback) throws Exception {
RetryLoop.callWithRetry(
zk.getZookeeperClient(),
new Callable<Void>() {
@Override
public Void call() throws Exception {
zk.checkExists().usingWatcher(callback).forPath(buildZookeeperPath(pathSuffix));
return null;
}
});
}
/**
* Optimistic concurrency scheme for tryAtomicUpdate. Try to update, and keep trying until
* successful.
*
* @param pathSuffix suffix to use to build path in ZooKeeper.
* @param f function used to initialize the node, or transform the data already there.
* @throws Exception
*/
private void atomicUpdate(final String pathSuffix, final NodeFunction f) throws Exception {
boolean done = false;
do {
done =
RetryLoop.callWithRetry(
zk.getZookeeperClient(),
new Callable<Boolean>() {
@Override
public Boolean call() throws Exception {
return tryAtomicUpdate(pathSuffix, f);
}
});
Thread.sleep(BASE_OPTIMISTIC_RETRY_TIME_MS + rand.nextInt(BASE_OPTIMISTIC_RETRY_TIME_MS));
} while (!done);
}
private void writeDataToPath(String path, String data) throws Exception {
ZKPaths.mkdirs(zookeeper.getZookeeperClient().getZooKeeper(), path);
zookeeper.setData().forPath(path, data.getBytes());
}