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https://issues.apache.org/jira/browse/ZOOKEEPER-2383?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15502828#comment-15502828
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Flavio Junqueira commented on ZOOKEEPER-2383:
---------------------------------------------
[~rakesh_r] the try/finally suggestion sounds good.
I have a couple more comments that I'm not sure we can address, but I have have
them written down at least:
# It sounds like you have covered all necessary {{zkServer == null}} cases, but
I'm concerned we might have missed any, I'm not sure there is a way of
guaranteeing and the only course of action is visual inspection. It'd be much
better if we could sort out the problem in the startup call instead of relying
on the methods accessing the {{zkServer}} to check whether the server is
running.
# The test case isn't covering the whole modified code. In particular, it is
not covering the 4lw changes this patch is making.
> 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
> Assignee: Rakesh R
> Priority: Blocker
> Fix For: 3.4.10, 3.5.3, 3.6.0
>
> Attachments: TestZkStandaloneJMXRegistrationRaceConcurrent.java,
> ZOOKEEPER-2383-br-3-4.patch, ZOOKEEPER-2383.patch, ZOOKEEPER-2383.patch,
> ZOOKEEPER-2383.patch, 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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