Jordan-
thanks for the advice!
Here are my follow-up questions:
* I can't find the 'getLockPath()" method on the InterProcessMutex or
InterProcessSemaphoreMutex
class
(I looked here: https://curator.apache.org/apidocs/index.html and couldn't
find a 'getLockPath()" method anywhere (the docs are version
2.5.1-snapshot, btw)
(I am using curator version 2.5.0)
* the InterProcessSemaphoreMutex does not allow revoking; so how will that
help?
On Tue, Sep 30, 2014 at 8:46 PM, Jordan Zimmerman <
[email protected]> wrote:
> 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.
>
> -JZ
>
>
> On September 30, 2014 at 4:19:58 PM, Singer, Jill ([email protected])
> wrote:
>
> 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.
> I 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 stack overflow.
>
> I'll cross-post answers if I have them.
> >>>>>>>>>>>>>
> 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");
> }
>
> }
>
> }
> }
>
>
