[jira] [Commented] (ZOOKEEPER-1875) NullPointerException in ClientCnxn$EventThread.processEvent

["Rakesh R (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-1875?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14020864#comment-14020864 ] 

Rakesh R commented on ZOOKEEPER-1875:
-------------------------------------

[~michim] When reviewing the code, I've come across one case where it can result in NPE. Zookeeper client.register(null) allows null watcher and during connection event the following code results in null watcher.

{code}
            case None:
                result.add(defaultWatcher);
                boolean clear = ClientCnxn.getDisableAutoResetWatch() &&
                        state != Watcher.Event.KeeperState.SyncConnected;
{code}

I've attached a patch to validate the null connection watcher at the api level. I hope this wont be a compatibility issue for 3.5 release?

> NullPointerException in ClientCnxn$EventThread.processEvent
> -----------------------------------------------------------
>
>                 Key: ZOOKEEPER-1875
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1875
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: java client
>    Affects Versions: 3.4.5
>            Reporter: Jerry He
>            Assignee: Jerry He
>            Priority: Minor
>             Fix For: 3.5.0
>
>         Attachments: ZOOKEEPER-1875-trunk.patch, ZOOKEEPER-1875.patch, ZOOKEEPER-1875.patch
>
>
> We've been seeing NullPointerException while working on HBase:
> {code}
> 14/01/30 22:15:25 INFO zookeeper.ZooKeeper: Client environment:user.dir=/home/biadmin/hbase-trunk
> 14/01/30 22:15:25 INFO zookeeper.ZooKeeper: Initiating client connection, connectString=hdtest009:2181 sessionTimeout=90000 watcher=null
> 14/01/30 22:15:25 INFO zookeeper.ClientCnxn: Opening socket connection to server hdtest009/9.30.194.18:2181. Will not attempt to authenticate using SASL (Unable to locate a login configuration)
> 14/01/30 22:15:25 INFO zookeeper.ClientCnxn: Socket connection established to hdtest009/9.30.194.18:2181, initiating session
> 14/01/30 22:15:25 INFO zookeeper.ClientCnxn: Session establishment complete on server hdtest009/9.30.194.18:2181, sessionid = 0x143986213e67e48, negotiated timeout = 60000
> 14/01/30 22:15:25 ERROR zookeeper.ClientCnxn: Error while calling watcher
> java.lang.NullPointerException
>         at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:519)
>         at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:495)
> {code}
> The reason is the watcher is null in this part of the code:
> {code}
>        private void processEvent(Object event) {
>           try {
>               if (event instanceof WatcherSetEventPair) {
>                   // each watcher will process the event
>                   WatcherSetEventPair pair = (WatcherSetEventPair) event;
>                   for (Watcher watcher : pair.watchers) {
>                       try {
>                           watcher.process(pair.event);
>                       } catch (Throwable t) {
>                           LOG.error("Error while calling watcher ", t);
>                       }
>                   }
> {code}



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