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https://issues.apache.org/jira/browse/ZOOKEEPER-2383?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15185412#comment-15185412
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Steve Rowe commented on ZOOKEEPER-2383:
---------------------------------------
FWIW, I was able to work around the problem in Solr tests by subclassing
ZooKeeperServer and ordering server JMX registration before setting up its
request processing pipeline, like so:
{code:java}
private class TestZooKeeperServer extends ZooKeeperServer {
@Override protected void registerJMX() {
// no-op - super.registerJMX() is called in overridden startup()
}
/** Register in JMX before starting the request processors. */
@Override public void startup() {
super.registerJMX();
super.startup();
}
public TestZooKeeperServer(FileTxnSnapLog txnLogFactory, int tickTime,
int minSessionTimeout, int maxSessionTimeout,
DataTreeBuilder treeBuilder, ZKDatabase zkDb) {
super(txnLogFactory, tickTime, minSessionTimeout, maxSessionTimeout,
treeBuilder, zkDb);
}
}
{code}
> Startup race in ZooKeeperServer
> -------------------------------
>
> Key: ZOOKEEPER-2383
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2383
> Project: ZooKeeper
> Issue Type: Bug
> Components: jmx, server
> Affects Versions: 3.4.8
> Reporter: Steve Rowe
> Priority: Blocker
> Fix For: 3.4.9
>
> Attachments: TestZkStandaloneJMXRegistrationRaceConcurrent.java,
> release-3.4.8-extra-logging.patch, zk-3.4.8-MBeanRegistry.log,
> zk-3.4.8-NPE.log
>
>
> In attempting to upgrade Solr's ZooKeeper dependency from 3.4.6 to 3.4.8
> (SOLR-8724) I ran into test failures where attempts to create a node in a
> newly started standalone ZooKeeperServer were failing because of an assertion
> in MBeanRegistry.
> ZooKeeperServer.startup() first sets up its request processor chain then
> registers itself in JMX, but if a connection comes in before the server's JMX
> registration happens, registration of the connection will fail because it
> trips the assertion that (effectively) its parent (the server) has already
> registered itself.
> {code:java|title=ZooKeeperServer.java}
> public synchronized void startup() {
> if (sessionTracker == null) {
> createSessionTracker();
> }
> startSessionTracker();
> setupRequestProcessors();
> registerJMX();
> state = State.RUNNING;
> notifyAll();
> }
> {code}
> {code:java|title=MBeanRegistry.java}
> public void register(ZKMBeanInfo bean, ZKMBeanInfo parent)
> throws JMException
> {
> assert bean != null;
> String path = null;
> if (parent != null) {
> path = mapBean2Path.get(parent);
> assert path != null;
> }
> {code}
> This problem appears to be new with ZK 3.4.8 - AFAIK Solr never had this
> issue with ZK 3.4.6.
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