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https://issues.apache.org/jira/browse/CURATOR-466?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16686530#comment-16686530
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Jordan Zimmerman commented on CURATOR-466:
------------------------------------------
Closing the Curator Handle closes the ZooKeeper Handle which closes the session
on the server. Thus, any ephemeral nodes associated with that session would get
deleted.
> LeaderSelector gets in an inconsistent state when releasing resources.
> ----------------------------------------------------------------------
>
> Key: CURATOR-466
> URL: https://issues.apache.org/jira/browse/CURATOR-466
> Project: Apache Curator
> Issue Type: Bug
> Components: Recipes
> Affects Versions: 4.0.1
> Reporter: Mikhail Pryakhin
> Priority: Major
>
> I'm using the leader election recipe that works well until I encountered
> application shutdown.
> here is my example:
>
> {code:java}
> CuratorFramework framework = CuratorFrameworkFactory.builder()
> .connectString("localhost:2181")
> .retryPolicy(new RetryOneTime(100))
> .build();
> LeaderSelector leaderSelector = new LeaderSelector(
> framework,
> "/path",
> new LeaderSelectorListener() {
> volatile boolean stopped;
> @Override
> public void takeLeadership(CuratorFramework client) throws Exception {
> System.out.println("I'm a new leader!");
> try {
> while (!Thread.currentThread().isInterrupted() && !stopped) {
> TimeUnit.SECONDS.sleep(1);
> }
> } finally {
> System.out.println("I'm not a leader anymore..");
> }
> }
> @Override
> public void stateChanged(CuratorFramework client, ConnectionState
> newState) {
> if
> (client.getConnectionStateErrorPolicy().isErrorState(newState)) {
> stopped = true;
> }
> }
> }
> );
> framework.start();
> leaderSelector.start();
> TimeUnit.SECONDS.sleep(5);
> leaderSelector.close(); //(1)
> framework.close(); //(2){code}
>
> When I release resources by calling close method first on the LeaderSelector
> instance and then on the CurtorFramework instance (lines 1 and 2) I always
> get the following exception:
>
> {code:java}
> java.lang.IllegalStateException: instance must be started before calling this
> method
> at
> org.apache.curator.shaded.com.google.common.base.Preconditions.checkState(Preconditions.java:444)
> ~[curator-client-4.0.1.jar:?]
> at
> org.apache.curator.framework.imps.CuratorFrameworkImpl.delete(CuratorFrameworkImpl.java:424)
> ~[curator-framework-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.recipes.locks.LockInternals.deleteOurPath(LockInternals.java:347)
> ~[curator-recipes-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.recipes.locks.LockInternals.releaseLock(LockInternals.java:124)
> ~[curator-recipes-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.recipes.locks.InterProcessMutex.release(InterProcessMutex.java:154)
> ~[curator-recipes-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.recipes.leader.LeaderSelector.doWork(LeaderSelector.java:449)
> [curator-recipes-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.recipes.leader.LeaderSelector.doWorkLoop(LeaderSelector.java:466)
> [curator-recipes-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.recipes.leader.LeaderSelector.access$100(LeaderSelector.java:65)
> [curator-recipes-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.recipes.leader.LeaderSelector$2.call(LeaderSelector.java:246)
> [curator-recipes-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.recipes.leader.LeaderSelector$2.call(LeaderSelector.java:240)
> [curator-recipes-4.0.1.jar:4.0.1]
> at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_141]
> at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
> [?:1.8.0_141]
> at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_141]
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> [?:1.8.0_141]
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> [?:1.8.0_141]
> at java.lang.Thread.run(Thread.java:748) [?:1.8.0_141]
> {code}
>
> The reason for the exception is that the non-blocking LeaderSelector.close
> method delegates call to the internal executor service, which abruptly
> cancels the running futures with the interptIfRunning flag set to true. Right
> after this, the CuratorFramework close method is called. By the meantime, the
> future being canceled executes the finally block where it calls methods on
> the already closed CuratorFramework instance which leads to throwing an
> exception.
> I thought I can wait a bit until the LeaderSelector instance is closed, so I
> tried to delay for some time before closing the CuratorFramework instance,
> but doing so leads to another exception:
> {code:java}
> ava.lang.InterruptedException: null
> at java.lang.Object.wait(Native Method) ~[?:1.8.0_141]
> at java.lang.Object.wait(Object.java:502) ~[?:1.8.0_141]
> at org.apache.zookeeper.ClientCnxn.submitRequest(ClientCnxn.java:1409)
> ~[zookeeper-3.4.12.jar:3.4.12--1]
> at org.apache.zookeeper.ZooKeeper.delete(ZooKeeper.java:874)
> ~[zookeeper-3.4.12.jar:3.4.12--1]
> at
> org.apache.curator.framework.imps.DeleteBuilderImpl$5.call(DeleteBuilderImpl.java:274)
> ~[curator-framework-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.imps.DeleteBuilderImpl$5.call(DeleteBuilderImpl.java:268)
> ~[curator-framework-4.0.1.jar:4.0.1]
> at
> org.apache.curator.connection.StandardConnectionHandlingPolicy.callWithRetry(StandardConnectionHandlingPolicy.java:64)
> ~[curator-client-4.0.1.jar:?]
> at org.apache.curator.RetryLoop.callWithRetry(RetryLoop.java:100)
> ~[curator-client-4.0.1.jar:?]
> at
> org.apache.curator.framework.imps.DeleteBuilderImpl.pathInForeground(DeleteBuilderImpl.java:265)
> ~[curator-framework-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.imps.DeleteBuilderImpl.forPath(DeleteBuilderImpl.java:249)
> ~[curator-framework-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.imps.DeleteBuilderImpl.forPath(DeleteBuilderImpl.java:34)
> ~[curator-framework-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.recipes.locks.LockInternals.deleteOurPath(LockInternals.java:347)
> ~[curator-recipes-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.recipes.locks.LockInternals.releaseLock(LockInternals.java:124)
> ~[curator-recipes-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.recipes.locks.InterProcessMutex.release(InterProcessMutex.java:154)
> ~[curator-recipes-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.recipes.leader.LeaderSelector.doWork(LeaderSelector.java:449)
> [curator-recipes-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.recipes.leader.LeaderSelector.doWorkLoop(LeaderSelector.java:466)
> [curator-recipes-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.recipes.leader.LeaderSelector.access$100(LeaderSelector.java:65)
> [curator-recipes-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.recipes.leader.LeaderSelector$2.call(LeaderSelector.java:246)
> [curator-recipes-4.0.1.jar:4.0.1]
> at
> org.apache.curator.framework.recipes.leader.LeaderSelector$2.call(LeaderSelector.java:240)
> [curator-recipes-4.0.1.jar:4.0.1]
> at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_141]
> at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
> [?:1.8.0_141]
> at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_141]
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> [?:1.8.0_141]
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> [?:1.8.0_141]
> at java.lang.Thread.run(Thread.java:748) [?:1.8.0_141]
> {code}
> At this time the exception is caused by the future being canceled with the
> interptIfRunning flag set to true in the LeaderSelector close method.
> As the LeaderSelector implementation is based on the InterPorcessMutex that
> works with ephemeral nodes, do we really need to manually clean up on
> shutdown? As far as I know, the ephemeral nodes are deleted when the client
> disconnects.
>
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