apache curator: lock revocation not working - multithreading

Question

short: I want to create a lock with one client and release it with another; so I am trying to use revocation for that end. It isn't working. more details (and my code) are below.
any help is appreciated!
long: have a system where one thread (with its own client) sets the first lock (update), then a second thread (with a client that may or may not be the same as the original client) will set a second lock; then do some work, then release that lock, and then release the first lock this code simulates two threads by having two different clients get locks.
the second client is unable to revoke the lock from the first client, however. the 'revocation listener' is never triggered. have scoured the web and not found examples.
this code assumes that you have a zookeeper server running on your local host at port 2181
ideally, I'd also like to look up from somewhere else real quick to see if the lock is in place, but perhaps an acquire with a very short timeout (5 milliseconds) would accomplish that.
also, is it a good idea to reap away locks after releasing them? (to not clog up the system?)
thanks
-Jill
ps: also posted on the apache curator user mailing list
I'll cross-post answers if I have them.
Got one answer from the mailing list: Jordan Zimmerman
8:46 PM (13 hours ago) There are a
number of problems:
The docs are not clear on this, but makeRevocable() must be called BEFORE the lock is acquired. Please submit a Jira/PR to fix the doc.
In your test, Revoker.attemptRevoke was using the incorrect path. It must be the path of the lock, so: "Revoker.attemptRevoke(client2,
ipMutex.getLockPath());”
InterProcessMutex keeps track of the thread that owns the lock. So, the lock.release(); in your revoker won’t work. I suggest using
InterProcessSemaphoreMutex instead.
import java.util.Collection;
import java.util.List;
import java.util.concurrent.TimeUnit;
import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.locks.InterProcessMutex;
import org.apache.curator.framework.recipes.locks.RevocationListener;
import org.apache.curator.framework.recipes.locks.Revoker;
import org.apache.curator.retry.ExponentialBackoffRetry;
public class MultipleClientExample {
/*entry point
*/
public static void main(String[] args){
RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 3);
String zookeeperConnectionString = "127.0.0.1:2181";
CuratorFramework client = CuratorFrameworkFactory.newClient(zookeeperConnectionString, retryPolicy);
client.start();
try {
System.out.println("testing locks....");
InterProcessMutex ipMutex = new InterProcessMutex(client, "/mpx-updates/guid123/update");
boolean acquired = ipMutex.acquire(3, TimeUnit.SECONDS);
System.out.println("got the lock(update)?" + acquired);
RevocationListener<InterProcessMutex> rl = new MyRevocationListener();
ipMutex.makeRevocable(rl);
InterProcessMutex ipMutex2 = new InterProcessMutex(client, "/mpx-updates/guid123/swap");
boolean a2 = ipMutex2.acquire(3, TimeUnit.SECONDS);
System.out.println("got the lock(swap)?" + a2);
System.out.println("got the first lock in this process? " + ipMutex.isAcquiredInThisProcess());
// make a new client; see if it can get the lock!
CuratorFramework client2 = CuratorFrameworkFactory.newClient(zookeeperConnectionString, retryPolicy);
client2.start();
InterProcessMutex ipMutex1Retry = new InterProcessMutex(client2, "/mpx-updates/guid123/update");
boolean a3 = ipMutex1Retry.acquire(3, TimeUnit.SECONDS);
System.out.println("got the lock(retry/update) ?" + a3);
System.out.println("got the first lock in this process? " + ipMutex1Retry.isAcquiredInThisProcess());
Revoker.attemptRevoke(client2, "/mpx-updates/guid123/update");
a3 = ipMutex1Retry.acquire(3, TimeUnit.SECONDS);
System.out.println("AGAIN: got the lock(retry/update) ?" + a3);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public class MyRevocationListener implements RevocationListener<InterProcessMutex> {
/*
* (non-Javadoc)
*
* #see org.apache.curator.framework.recipes.locks.RevocationListener#revocationRequested(java.lang.Object)
*/
#Override
public void revocationRequested(InterProcessMutex lock) {
//this seems to never be called
Collection<String> participantNodes = null;
try {
System.out.println("revocation was requested....");
System.out.println("ick ick revocation requested....");
participantNodes = lock.getParticipantNodes();
lock.release();
System.out.println("revoked lock at path: " + participantNodes);
} catch (Exception e) {
System.out.println("problem revoking lock with path: " + participantNodes + "; it was not revoked");
}
}
}
}