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https://issues.apache.org/jira/browse/HBASE-5289?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13194175#comment-13194175
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Zhihong Yu commented on HBASE-5289:
-----------------------------------
Thanks for reporting this case, Krystian.
Do you want to upload a patch ?
> NullPointerException in resetZooKeeperTrackers in HConnectionManager /
> HConnectionImplementation
> ------------------------------------------------------------------------------------------------
>
> Key: HBASE-5289
> URL: https://issues.apache.org/jira/browse/HBASE-5289
> Project: HBase
> Issue Type: Bug
> Components: client
> Affects Versions: 0.90.5
> Reporter: Krystian Nowak
> Fix For: 0.94.0, 0.92.1
>
>
> This might happen on heavy load in case of lagging HBase when sharing one
> HConnection by multiple threads:
> {noformat}
> 2012-01-26 13:59:38,396 ERROR [http://*:8080-251-EventThread]
> zookeeper.ClientCnxn$EventThread(532): Error while calling watcher
> java.lang.NullPointerException
> at
> org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.resetZooKeeperTrackers(HConnectionManager.java:533)
> at
> org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.abort(HConnectionManager.java:1536)
> at
> org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher.connectionEvent(ZooKeeperWatcher.java:344)
> at
> org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher.process(ZooKeeperWatcher.java:262)
> at
> org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:530)
> at
> org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:506)
> {noformat}
> The following code is not protected against NPE:
> {code}
> private synchronized void resetZooKeeperTrackers()
> throws ZooKeeperConnectionException {
> LOG.info("Trying to reconnect to zookeeper");
> masterAddressTracker.stop();
> masterAddressTracker = null;
> rootRegionTracker.stop();
> rootRegionTracker = null;
> clusterId = null;
> this.zooKeeper = null;
> setupZookeeperTrackers();
> }
> {code}
> In some cases as proven by the log snippet above it might happen that either
> masterAddressTracker or rootRegionTracker might be null.
> Because of the NPE the code can't reach setupZookeeperTrackers() call.
> This should be fixed at least the way as shown in one of the patches in
> HBASE-5153
> {code}
> LOG.info("Trying to reconnect to zookeeper.");
> if (this.masterAddressTracker != null) {
> this.masterAddressTracker.stop();
> this.masterAddressTracker = null;
> }
> if (this.rootRegionTracker != null) {
> this.rootRegionTracker.stop();
> this.rootRegionTracker = null;
> }
> {code}
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