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https://issues.apache.org/jira/browse/HBASE-2669?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12875915#action_12875915
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stack commented on HBASE-2669:
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In old days, we had similar prob w/ hdfs. We wanted to run a shutdown cleanup
of hbase hook but hdfs would be running its clean up at same time and we
couldn't guarantee order.
Using reflection, we looked for hdsf hook, if present, unregistered it but kept
a reference and then in our shutdown hook, after was done, we'd call the hdfs
one. Lets fix this benoit. Mind if I move it out of 0.20.5 though? Its a
prob. but not end of world and I'd like to get a 0.20.5 rolled today. Thanks.
> HCM.shutdownHook causes data loss with hbase.client.write.buffer != 0
> ---------------------------------------------------------------------
>
> Key: HBASE-2669
> URL: https://issues.apache.org/jira/browse/HBASE-2669
> Project: HBase
> Issue Type: Bug
> Components: client
> Reporter: Benoit Sigoure
> Assignee: Benoit Sigoure
> Priority: Critical
> Fix For: 0.20.5
>
>
> In my application I set {{hbase.client.write.buffer}} to a reasonably small
> value (roughly 64 edits) in order to try to batch a few {{Put}} together
> before talking to HBase. When my application does a graceful shutdown, I
> call {{HTable#flushCommits}} in order to flush any pending change to HBase.
> I want to do the same thing when I get a {{SIGTERM}} by using
> {{Runtime#addShutdownHook}} but this is impossible since
> {{HConnectionManager}} already registers a shutdown hook that invokes
> {{HConnectionManager#deleteAllConnections}}. This static method closes all
> the connections to HBase and then all connections to ZooKeeper. Because all
> shutdown hooks run in parallel, my hook will attempt to flush edits while
> connections are getting closed.
> There is no way to guarantee the order in which the hooks will execute, so I
> propose that we remove the hook in the HCM altogether and provide some
> user-visible API they call in their own hook after they're done flushing
> their stuff, if they really want to do a graceful shutdown. I expect that a
> lot of users won't use a hook though, otherwise this issue would have cropped
> up already. For those users, connections won't get "gracefully" terminated,
> but I don't think that would be a problem since the underlying TCP socket
> will get closed by the OS anyway, so things like ZooKeeper and such should
> realize that the connection has been terminated and assume the client is
> gone, and do the necessary clean-up on their side.
> An alternate fix would be to leave the hook in place by default but keep a
> reference to it and add a user-visible API to be able to un-register the
> hook. I find this ugly.
> Thoughts?
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