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From "jiraposter@reviews.apache.org (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5209) HConnection/HMasterInterface should allow for way to get hostname of currently active master in multi-master HBase setup
Date Tue, 14 Feb 2012 18:52:02 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5209?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13207901#comment-13207901
] 

jiraposter@reviews.apache.org commented on HBASE-5209:
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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/3892/
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(Updated 2012-02-14 18:50:54.512575)


Review request for hbase.


Changes
-------

Addressed changes that Ted suggested.


Summary
-------

Problem:
There is no method in the HBase client-facing APIs to determine which of the masters is currently
active.  This can be especially useful in setups with multiple backup masters.

Solution:
Augment ClusterStatus to return the currently active master and the list of backup masters.

Notes:
* I uncovered a race condition in ActiveMasterManager, between when it determines that it
did not win the original race to be the active master, and when it reads the ServerName of
the active master.  If the active master goes down in that time, the read to determine the
active master's ServerName will fail ungracefully and the candidate master will abort.  The
solution incorporated in this patch is to check to see if the read of the ServerName succeeded
before trying to use it.
* I fixed some minor formatting issues while going through the code.  I can take these changes
out if it is considered improper to commit such non-related changes with the main changes.


This addresses bug HBASE-5209.
    https://issues.apache.org/jira/browse/HBASE-5209


Diffs (updated)
-----

  src/main/java/org/apache/hadoop/hbase/ClusterStatus.java b849429 
  src/main/java/org/apache/hadoop/hbase/master/ActiveMasterManager.java 2f60b23 
  src/main/java/org/apache/hadoop/hbase/master/HMaster.java 9d21903 
  src/main/java/org/apache/hadoop/hbase/util/HBaseFsck.java f6f3f71 
  src/main/java/org/apache/hadoop/hbase/zookeeper/ZKUtil.java 111f76e 
  src/main/java/org/apache/hadoop/hbase/zookeeper/ZooKeeperWatcher.java 3e3d131 
  src/test/java/org/apache/hadoop/hbase/master/TestActiveMasterManager.java 16e4744 
  src/test/java/org/apache/hadoop/hbase/master/TestMasterFailover.java bc98fb0 

Diff: https://reviews.apache.org/r/3892/diff


Testing
-------

* Ran mvn -P localTests test multiple times - no new tests fail
* Ran mvn -P localTests -Dtest=TestActiveMasterManager test multiple runs - no failures
* Ran mvn -P localTests -Dtest=TestMasterFailover test multiple runs - no failures
* Started active and multiple backup masters, then killed active master, then brought it back
up (will now be a backup master)
  * Did the following before and after killing
    * hbase fsck - checked output to see that active and backup masters are reported properly
    * zk_dump - checked that active and backup masters are reported properly
* Started cluster with no backup masters to make sure change operates correctly that way
* Ran dev-support/test-patch.sh - no new issues fail:

-1 overall.

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

    +1 tests included.  The patch appears to include 7 new or modified tests.

    -1 javadoc.  The javadoc tool appears to have generated -136 warning messages.  

    +1 javac.  The applied patch does not increase the total number of javac compiler warnings.

    +1 findbugs.  The patch does not introduce any new Findbugs (version ) warnings.

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


Thanks,

David


                
> HConnection/HMasterInterface should allow for way to get hostname of currently active
master in multi-master HBase setup
> ------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-5209
>                 URL: https://issues.apache.org/jira/browse/HBASE-5209
>             Project: HBase
>          Issue Type: Improvement
>          Components: master
>    Affects Versions: 0.94.0, 0.90.5, 0.92.0
>            Reporter: Aditya Acharya
>            Assignee: David S. Wang
>             Fix For: 0.94.0, 0.90.7, 0.92.1
>
>         Attachments: HBASE-5209-v0.diff, HBASE-5209-v1.diff
>
>
> I have a multi-master HBase set up, and I'm trying to programmatically determine which
of the masters is currently active. But the API does not allow me to do this. There is a getMaster()
method in the HConnection class, but it returns an HMasterInterface, whose methods do not
allow me to find out which master won the last race. The API should have a getActiveMasterHostname()
or something to that effect.

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