[jira] [Comment Edited] (STORM-2415) Storm fails to properly handle Zookeeper hosts going down

["Anthony Milbourne (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/STORM-2415?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15925850#comment-15925850 ] 

Anthony Milbourne edited comment on STORM-2415 at 3/15/17 10:22 AM:
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This issue was created as a result of discussion on STORM-2290.


was (Author: amilbourne):
This issue was created as a result of discussion on the previous issue.

> Storm fails to properly handle Zookeeper hosts going down
> ---------------------------------------------------------
>
>                 Key: STORM-2415
>                 URL: https://issues.apache.org/jira/browse/STORM-2415
>             Project: Apache Storm
>          Issue Type: Bug
>          Components: storm-core
>    Affects Versions: 1.0.3
>         Environment: All
>            Reporter: Anthony Milbourne
>
> We run a storm cluster (v.1.0.3) on AWS and have 3 Zookeepers supporting it. Because AWS sometimes terminates VMs, we sometimes lose a Zookeeper instance. When this happens, the hostname cannot be resolved for that zookeeper instance as AWS has taken the VM away. We noticed that in this case storm fails to connect to zookeeper – even though there are still 2 Zookeeper instances running. It fails with an exception something like:
> {noformat}
> java.net.UnknownHostException: zookeeper3
>   at java.net.InetAddress.getAllByName0(InetAddress.java:1280) 
>   at java.net.InetAddress.getAllByName(InetAddress.java:1192) 
>   at java.net.InetAddress.getAllByName(InetAddress.java:1126) 
>   at org.apache.storm.shade.org.apache.zookeeper.client.StaticHostProvider.<init>(StaticHostProvider.java:61) 
>   at org.apache.storm.shade.org.apache.zookeeper.ZooKeeper.<init>(ZooKeeper.java:445) 
>   at org.apache.storm.shade.org.apache.curator.utils.DefaultZookeeperFactory.newZooKeeper(DefaultZookeeperFactory.java:29) 
>   at org.apache.storm.shade.org.apache.curator.framework.imps.CuratorFrameworkImpl$2.newZooKeeper(CuratorFrameworkImpl.java:150) 
>   at org.apache.storm.shade.org.apache.curator.HandleHolder$1.getZooKeeper(HandleHolder.java:94) 
>   at org.apache.storm.shade.org.apache.curator.HandleHolder.getZooKeeper(HandleHolder.java:55) 
>   at org.apache.storm.shade.org.apache.curator.ConnectionState.reset(ConnectionState.java:218) 
>   at org.apache.storm.shade.org.apache.curator.ConnectionState.start(ConnectionState.java:103) 
>   at org.apache.storm.shade.org.apache.curator.CuratorZookeeperClient.start(CuratorZookeeperClient.java:190) 
>   at org.apache.storm.shade.org.apache.curator.framework.imps.CuratorFrameworkImpl.start(CuratorFrameworkImpl.java:259) 
>   at org.apache.storm.zookeeper$mk_client.doInvoke(zookeeper.clj:86) 
>   at clojure.lang.RestFn.invoke(RestFn.java:494)
>   at org.apache.storm.cluster_state.zookeeper_state_factory$_mkState.invoke(zookeeper_state_factory.clj:28) 
>   at org.apache.storm.cluster_state.zookeeper_state_factory.mkState(Unknown Source) 
>   <SNIP REST OF STACKTRACE>
> {noformat}
> Having done some research it looks like this error is caused by a bug in the Zookeeper client library. There is an issue for it here:
> [https://issues.apache.org/jira/browse/ZOOKEEPER-1576]
> This issue has been resolved in the version 3.5.x branch of Zookeeper. However, after 2.5 years and 3 releases the 3.5.x branch of Zookeeper is still in Alpha .
> Despite the fact that it is in alpha, there is a branch of Curator (v.3.x.x) that uses it, but Storm uses Curator version 2.x.x – possibly because it doesn’t rely on alpha code. So the bug is still unpatched in Storm.
> I realise that an upgrade to alpha code may be too much of a risk, but this problem is a serious issue for those running Storm in a containerised or cloud environment - so perhaps it may be worth considering?



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