[
https://issues.apache.org/jira/browse/CURATOR-527?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16856836#comment-16856836
]
Kim Jaechang commented on CURATOR-527:
--------------------------------------
[~randgalt] The case I said was node deleted after getData() called and before
wait() called.
I checked from thread dump that localvariable for
lock-759(previousSequencePath) and lock-760(ourPath) exist but in zookeeper,
only lock-760 exist.
I am sorry I can't upload my original test code because current project is not
open-source project.
I'll leave pseudo code for my case. multiple instances was running concurrently.
{code:java}
private abstract class BaseWatcher implements CuratorWatcher {
private InterProcessMutex lock;
private final String objectPath = "/object";
private final String lockPath = "/lock";
private String namespace;
BaseWatcher() {
this.lock = new InterProcessMutex(this.zooKeeperClient, this.namespace +
lockPath);
}
@Override
public abstract void process(WatchedEvent watchedEvent);
protected void lock() throws Exception {
this.lock.acquire();
}
protected void unlock() throws Exception {
if (this.lock.isAcquiredInThisProcess()) {
this.lock.release();
}
}
protected void registerWatcher(CuratorWatcher watcher, boolean isWatcher2)
throws Exception {
if (isWatcher2) {
this.zooKeeperClient.checkExists().usingWatcher(watcher).forPath(namespace +
PathforWatcher2);
} else {
this.zooKeeperClient.checkExists().usingWatcher(watcher).forPath(namespace +
objectPath);
}
}
protected void updateObject(Byte[] data){
this.zooKeeperClient.setData().forPath(namespace + objectPath, data);
}
}
private class Watcher1 extends BaseWatcher {
@Override
public void process(WatchedEvent watchedEvent) {
try {
super.lock();
registerWatcher(this, false);
super.unlock();
}
}
}
private class Watcher2 extends BaseWatcher {
@Override
public void process(WatchedEvent watchedEvent) {
try {
super.lock();
super.updateObject(contents);
super.unlock();
super.registerWatcher(this, true);
}
}
}
{code}
> Concurrency issue in LockInternals
> ----------------------------------
>
> Key: CURATOR-527
> URL: https://issues.apache.org/jira/browse/CURATOR-527
> Project: Apache Curator
> Issue Type: Bug
> Components: Recipes
> Affects Versions: 2.12.0
> Environment: Curator 2.12.0
> zookeeper 3.4.14
> Reporter: Kim Jaechang
> Priority: Major
>
> I'm using InterProcessMutex and InterProcessMutex often failed to acquire
> lock.
> In LockInternals.internalLockLoop(), watcher is registered to zookeeper and
> call wait() like below
> {code:java}
> client.getData().usingWatcher(watcher).forPath(previousSequencePath);
> if ( millisToWait != null )
> {
> millisToWait -= (System.currentTimeMillis() - startMillis);
> startMillis = System.currentTimeMillis();
> if ( millisToWait <= 0 )
> {
> doDelete = true; // timed out - delete our node
> break;
> }
> wait(millisToWait);
> }
> else
> {
> wait();
> }
> {code}
> In my case, my program is waiting
> previousSequencePath=_c_f290140d-9856-42ad-b9bf-348ffc086062-lock-0000000759
> to be deleted.
> But _c_f290140d-9856-42ad-b9bf-348ffc086062-lock-0000000759 is deleted
> between client.getData() and wait().
> if _c_f290140d-9856-42ad-b9bf-348ffc086062-lock-0000000759 is deleted when
> client.getData().usingWatcher(watcher).forPath(previousSequencePath) is
> called, it will throw Exception but it was exist at that time.
> I'm using Curator 2.12.0 but latest version seems to have same issue.
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
