[jira] Updated: (HBASE-1316) ZooKeeper: use native threads to avoid GC stalls (JNI integration)

["Joey Echeverria (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-1316?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Joey Echeverria updated HBASE-1316:
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    Attachment: zk_wrapper.tar.gz

I'm uploading a tarball with the basic wrapper we used to get around GC pauses. The C code maintains it's own session with zk which is independent of any java sessions. If you want to do anything other than create ephemeral nodes, more functions need to be wrapped or a combination of C and Java is needed.

I could try and build something more comprehensive, potentially even a full implementation of the Java API which completely wraps the C, but I wanted to show you guys what I had at this stage. Let me know if you have any questions.

> ZooKeeper: use native threads to avoid GC stalls (JNI integration)
> ------------------------------------------------------------------
>
>                 Key: HBASE-1316
>                 URL: https://issues.apache.org/jira/browse/HBASE-1316
>             Project: Hadoop HBase
>          Issue Type: Improvement
>    Affects Versions: 0.20.0
>            Reporter: Andrew Purtell
>         Attachments: zk_wrapper.tar.gz
>
>
> From Joey Echeverria up on hbase-users@:
> We've used zookeeper in a write-heavy project we've been working on and experienced issues similar to what you described. After several days of debugging, we discovered that our issue was garbage collection. There was no way to guarantee we wouldn't have long pauses especially since our environment was the worst case for garbage collection, millions of tiny, short lived objects. I suspect HBase sees similar work loads frequently, if it's not constantly. With anything shorter than a 30 second session time out, we got session expiration events extremely frequently. We needed to use 60 seconds for any real confidence that an ephemeral node disappearing meant something was unavailable.
> We really wanted quick recovery so we ended up writing a light-weight wrapper around the C API and used swig to auto-generate a JNI interface. It's not perfect, but since we switched to this method we've never seen a session expiration event and ephemeral nodes only disappear when there are network issues or a machine/process goes down.
> I don't know if it's worth doing the same kind of thing for HBase as it adds some "unnecessary" native code, but it's a solution that I found works.

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