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https://issues.apache.org/jira/browse/HBASE-1316?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12726832#action_12726832
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Joey Echeverria commented on HBASE-1316:
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We specifically avoided having any callbacks cross the C/Java boundary This was
simple in our use case where the only thing we needed to monitor after creating
an ephemeral node was whether or ZK session had expired. We also had a very
simple recovery mechanism, we immediately kill the process that got
disconnected and the shell script that launched us will relaunch. This proved
far easier than trying to re-establish a connection to ZK in the running
process.
> 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
> Assignee: Nitay Joffe
> 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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