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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6364) Powering down the server host holding the .META. table causes HBase Client to take excessively long to recover and connect to reassigned .META. table
Date Sun, 05 Aug 2012 17:54:02 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6364?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13428886#comment-13428886

Hadoop QA commented on HBASE-6364:

-1 overall.  Here are the results of testing the latest attachment 
  against trunk revision .

    +1 @author.  The patch does not contain any @author tags.

    -1 tests included.  The patch doesn't appear to include any new or modified tests.
                        Please justify why no new tests are needed for this patch.
                        Also please list what manual steps were performed to verify this patch.

    +1 hadoop2.0.  The patch compiles against the hadoop 2.0 profile.

    +1 javadoc.  The javadoc tool did not generate any warning messages.

    -1 javac.  The applied patch generated 5 javac compiler warnings (more than the trunk's
current 4 warnings).

    -1 findbugs.  The patch appears to introduce 9 new Findbugs (version 1.3.9) warnings.

    +1 release audit.  The applied patch does not increase the total number of release audit

     -1 core tests.  The patch failed these unit tests:

Test results: https://builds.apache.org/job/PreCommit-HBASE-Build/2513//testReport/
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/2513//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-hadoop2-compat.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/2513//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-server.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/2513//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-hadoop1-compat.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/2513//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-common.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/2513//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-hadoop-compat.html
Console output: https://builds.apache.org/job/PreCommit-HBASE-Build/2513//console

This message is automatically generated.
> Powering down the server host holding the .META. table causes HBase Client to take excessively
long to recover and connect to reassigned .META. table
> -----------------------------------------------------------------------------------------------------------------------------------------------------
>                 Key: HBASE-6364
>                 URL: https://issues.apache.org/jira/browse/HBASE-6364
>             Project: HBase
>          Issue Type: Bug
>          Components: client
>    Affects Versions: 0.90.6, 0.92.1, 0.94.0
>            Reporter: Suraj Varma
>            Assignee: nkeywal
>              Labels: client
>         Attachments: 6364.v1.patch, stacktrace.txt
> When a server host with a Region Server holding the .META. table is powered down on a
live cluster, while the HBase cluster itself detects and reassigns the .META. table, connected
HBase Client's take an excessively long time to detect this and re-discover the reassigned
> Workaround: Decrease the ipc.socket.timeout on HBase Client side to a low  value (default
is 20s leading to 35 minute recovery time; we were able to get acceptable results with 100ms
getting a 3 minute recovery) 
> This was found during some hardware failure testing scenarios. 
> Test Case:
> 1) Apply load via client app on HBase cluster for several minutes
> 2) Power down the region server holding the .META. server (i.e. power off ... and keep
it off)
> 3) Measure how long it takes for cluster to reassign META table and for client threads
to re-lookup and re-orient to the lesser cluster (minus the RS and DN on that host).
> Observation:
> 1) Client threads spike up to maxThreads size ... and take over 35 mins to recover (i.e.
for the thread count to go back to normal) - no client calls are serviced - they just back
up on a synchronized method (see #2 below)
> 2) All the client app threads queue up behind the oahh.ipc.HBaseClient#setupIOStreams
method http://tinyurl.com/7js53dj
> After taking several thread dumps we found that the thread within this synchronized method
was blocked on  NetUtils.connect(this.socket, remoteId.getAddress(), getSocketTimeout(conf));
> The client thread that gets the synchronized lock would try to connect to the dead RS
(till socket times out after 20s), retries, and then the next thread gets in and so forth
in a serial manner.
> Workaround:
> -------------------
> Default ipc.socket.timeout is set to 20s. We dropped this to a low number (1000 ms, 
100 ms, etc) on the client side hbase-site.xml. With this setting, the client threads recovered
in a couple of minutes by failing fast and re-discovering the .META. table on a reassigned
> Assumption: This ipc.socket.timeout is only ever used during the initial "HConnection"
setup via the NetUtils.connect and should only ever be used when connectivity to a region
server is lost and needs to be re-established. i.e it does not affect the normal "RPC" actiivity
as this is just the connect timeout.
> During RS GC periods, any _new_ clients trying to connect will fail and will require
.META. table re-lookups.
> This above timeout workaround is only for the HBase client side.

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