/**
* Returns the current value of the counter. NOTE: if the value has never been set, <code>0</code>
* is returned.
*
* @return value info
* @throws Exception ZooKeeper errors
*/
public AtomicValue<byte[]> get() throws Exception {
MutableAtomicValue<byte[]> result = new MutableAtomicValue<byte[]>(null, null, false);
getCurrentValue(result, new Stat());
result.postValue = result.preValue;
result.succeeded = true;
return result;
}
/**
* Atomically sets the value to the given updated value if the current value {@code ==} the
* expected value. Remember to always check {@link AtomicValue#succeeded()}.
*
* @param expectedValue the expected value
* @param newValue the new value
* @return value info
* @throws Exception ZooKeeper errors
*/
public AtomicValue<byte[]> compareAndSet(byte[] expectedValue, byte[] newValue) throws Exception {
Stat stat = new Stat();
MutableAtomicValue<byte[]> result = new MutableAtomicValue<byte[]>(null, null, false);
boolean createIt = getCurrentValue(result, stat);
if (!createIt && Arrays.equals(expectedValue, result.preValue)) {
try {
client.setData().withVersion(stat.getVersion()).forPath(path, newValue);
result.succeeded = true;
result.postValue = newValue;
} catch (KeeperException.BadVersionException dummy) {
result.succeeded = false;
} catch (KeeperException.NoNodeException dummy) {
result.succeeded = false;
}
} else {
result.succeeded = false;
}
return result;
}
private boolean tryOnce(MutableAtomicValue<byte[]> result, MakeValue makeValue) throws Exception {
Stat stat = new Stat();
boolean createIt = getCurrentValue(result, stat);
boolean success = false;
try {
byte[] newValue = makeValue.makeFrom(result.preValue);
if (createIt) {
client.create().forPath(path, newValue);
} else {
client.setData().withVersion(stat.getVersion()).forPath(path, newValue);
}
result.postValue = Arrays.copyOf(newValue, newValue.length);
success = true;
} catch (KeeperException.NodeExistsException e) {
// do Retry
} catch (KeeperException.BadVersionException e) {
// do Retry
} catch (KeeperException.NoNodeException e) {
// do Retry
}
return success;
}
