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https://issues.apache.org/jira/browse/ZOOKEEPER-1214?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13572143#comment-13572143
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Edward Ribeiro commented on ZOOKEEPER-1214:
-------------------------------------------
https://issues.apache.org/jira/browse/ZOOKEEPER-1214
Hi Michi,
My two cents: this looks like a bug in ReentrantReadWriteLock, the JVM, or even
an incorrect use of _ReentrantReadWriteLock_ by JmxMBeanServer. I say so
because a quick Google search shows that other projects that use
ReentrantReadWriteLock, *directly or not*, as HBase, Netbeans and Maven have
hit this very same exception.
As ZooKeeper uses _ReentrantReadWriteLock_ indirectly through JmxMBeanServer, a
possible solution seems to be to create a lock object and synchronize lines 98
and 117 of JmxMBeanServer as follows:
{code:title=JmxMBeanServer.java|borderStyle=solid}
...
private final Object LOCK = new Object();
...
// line 98 becomes
synchronize (LOCK) {
mBeanServer.registerMBean(bean, oname);
}
// line 117 becomes
synchronize (LOCK) {
mBeanServer.unregisterMBean(makeObjectName(path, bean));
}
{code}
As this is a issue addressed to Cesar I'll not submit a patch, but I may
provide you a patch by email to see if this solution works.;)
Cheers,
Edward
> QuorumPeer should unregister only its previsously registered MBeans instead
> of use MBeanRegistry.unregisterAll() method.
> ------------------------------------------------------------------------------------------------------------------------
>
> Key: ZOOKEEPER-1214
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1214
> Project: ZooKeeper
> Issue Type: Bug
> Components: quorum
> Reporter: César Álvarez Núñez
> Assignee: César Álvarez Núñez
> Fix For: 3.5.0
>
> Attachments: ZOOKEEPER-1214.patch, ZOOKEEPER-1214.patch,
> ZOOKEEPER-1214.patch
>
>
> When a QuorumPeer thread dies, it is unregistering *all* ZKMBeanInfo MBeans
> previously registered on its java process; including those that has not been
> registered by itself.
> It does not cause any side effect in production environment where each server
> is running on a separate java process; but fails when using
> "org.apache.zookeeper.test.QuorumUtil" to programmatically start up a
> zookeeper server ensemble and use its provided methods to force Disconnected,
> SyncConnected or SessionExpired events; in order to perform some
> basic/functional testing.
> Scenario:
> * QuorumUtil qU = new QuorumUtil(1); // It creates a 3 servers ensemble.
> * qU.startAll(); // Startup all servers: 1 Leader + 2 Followers
> * qU.shutdown\(i\); // i is a number from 1 to 3. It shutdown one server.
> The last method causes that a QuorumPeer will die, invoking the
> MBeanRegistry.unregisterAll() method.
> As a result, *all* ZKMBeanInfo MBeans are unregistered; including those
> belonging to the other QuorumPeer instances.
> When trying to restart previous server (qU.restart\(i\)) an AssertionError is
> thrown at MBeanRegistry.register(ZKMBeanInfo bean, ZKMBeanInfo parent)
> method, causing the QuorumPeer thread dead.
> To solve it:
> * MBeanRegistry.unregisterAll() method has been removed.
> * QuorumPeer only unregister its ZKMBeanInfo MBeans.
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