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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 19:36:00 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5209?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13207940#comment-13207940
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jiraposter@reviews.apache.org commented on HBASE-5209:
------------------------------------------------------



bq.  On 2012-02-14 19:01:02, Michael Stack wrote:
bq.  > src/main/java/org/apache/hadoop/hbase/ClusterStatus.java, line 278
bq.  > <https://reviews.apache.org/r/3892/diff/2/?file=74894#file74894line278>
bq.  >
bq.  >     Isn't this Writable versioned?   Should you up the version since you've added
fields and check the version when deserializing (if you get a previous version, don't try
and derserialize master and backupmasters)
bq.  
bq.  David Wang wrote:
bq.      I took the lead from your commit at SHA b8b142a9e10aa729e0c0d4560035b1bdc4a0bd5c,
where you bumped VERSION, and I didn't notice any special handling about checking for previous
versions.  I can easily add that if necessary, though since I am adding to the end of the
Writable, do I need to?

Yeah, that commit should have upped the version too... (I think this is the commit that added
it):


commit 65e23155db94d4b3f36c35e90089f5827dea549b
Author: Andrew Kyle Purtell <apurtell@apache.org>
Date:   Mon Oct 24 23:18:04 2011 +0000

    HBASE-4070  Improve region server metrics to report loaded coprocessors to master
    
    git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1188442 13f79535-47bb-0310-9956-ffa450edef68


bq.  On 2012-02-14 19:01:02, Michael Stack wrote:
bq.  > src/main/java/org/apache/hadoop/hbase/master/ActiveMasterManager.java, line 182
bq.  > <https://reviews.apache.org/r/3892/diff/2/?file=74895#file74895line182>
bq.  >
bq.  >     You don't think this setStatus needed anymore?
bq.  
bq.  David Wang wrote:
bq.      Actually, this is still being called.  I just pulled out the setStatus() and Log.info()
calls since they apply to all three of the cases in this block.  Now the three cases in this
block are just setting msg.

Ok.  Good.


bq.  On 2012-02-14 19:01:02, Michael Stack wrote:
bq.  > src/main/java/org/apache/hadoop/hbase/master/HMaster.java, line 1393
bq.  > <https://reviews.apache.org/r/3892/diff/2/?file=74896#file74896line1393>
bq.  >
bq.  >     List is a Collection.  Why convert to a Set?  Is it needed?
bq.  >     
bq.  >     If you have to do the convertion, use http://docs.oracle.com/javase/1.5.0/docs/api/java/util/Collections.html#addAll(java.util.Collection,
T...) instead?
bq.  
bq.  David Wang wrote:
bq.      I used Set instead of List because I figured backupMasters is very similar in concept
to deadServers, which is an instance of DeadServer that uses Set.
bq.      
bq.      Also, List is ordered while Set is not.  And I don't think backupMasters or deadServers
are meant to be ordered.

Not that important I'd say.  Just do List I'd say.


- Michael


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On 2012-02-14 18:50:54, David Wang wrote:
bq.  
bq.  -----------------------------------------------------------
bq.  This is an automatically generated e-mail. To reply, visit:
bq.  https://reviews.apache.org/r/3892/
bq.  -----------------------------------------------------------
bq.  
bq.  (Updated 2012-02-14 18:50:54)
bq.  
bq.  
bq.  Review request for hbase.
bq.  
bq.  
bq.  Summary
bq.  -------
bq.  
bq.  Problem:
bq.  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.
bq.  
bq.  Solution:
bq.  Augment ClusterStatus to return the currently active master and the list of backup masters.
bq.  
bq.  Notes:
bq.  * 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.
bq.  * 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.
bq.  
bq.  
bq.  This addresses bug HBASE-5209.
bq.      https://issues.apache.org/jira/browse/HBASE-5209
bq.  
bq.  
bq.  Diffs
bq.  -----
bq.  
bq.    src/main/java/org/apache/hadoop/hbase/ClusterStatus.java b849429 
bq.    src/main/java/org/apache/hadoop/hbase/master/ActiveMasterManager.java 2f60b23 
bq.    src/main/java/org/apache/hadoop/hbase/master/HMaster.java 9d21903 
bq.    src/main/java/org/apache/hadoop/hbase/util/HBaseFsck.java f6f3f71 
bq.    src/main/java/org/apache/hadoop/hbase/zookeeper/ZKUtil.java 111f76e 
bq.    src/main/java/org/apache/hadoop/hbase/zookeeper/ZooKeeperWatcher.java 3e3d131 
bq.    src/test/java/org/apache/hadoop/hbase/master/TestActiveMasterManager.java 16e4744 
bq.    src/test/java/org/apache/hadoop/hbase/master/TestMasterFailover.java bc98fb0 
bq.  
bq.  Diff: https://reviews.apache.org/r/3892/diff
bq.  
bq.  
bq.  Testing
bq.  -------
bq.  
bq.  * Ran mvn -P localTests test multiple times - no new tests fail
bq.  * Ran mvn -P localTests -Dtest=TestActiveMasterManager test multiple runs - no failures
bq.  * Ran mvn -P localTests -Dtest=TestMasterFailover test multiple runs - no failures
bq.  * Started active and multiple backup masters, then killed active master, then brought
it back up (will now be a backup master)
bq.    * Did the following before and after killing
bq.      * hbase fsck - checked output to see that active and backup masters are reported
properly
bq.      * zk_dump - checked that active and backup masters are reported properly
bq.  * Started cluster with no backup masters to make sure change operates correctly that
way
bq.  * Ran dev-support/test-patch.sh - no new issues fail:
bq.  
bq.  -1 overall.
bq.  
bq.      +1 @author.  The patch does not contain any @author tags.
bq.  
bq.      +1 tests included.  The patch appears to include 7 new or modified tests.
bq.  
bq.      -1 javadoc.  The javadoc tool appears to have generated -136 warning messages.  
bq.  
bq.      +1 javac.  The applied patch does not increase the total number of javac compiler
warnings.
bq.  
bq.      +1 findbugs.  The patch does not introduce any new Findbugs (version ) warnings.
bq.  
bq.      +1 release audit.  The applied patch does not increase the total number of release
audit warnings.
bq.  
bq.  
bq.  Thanks,
bq.  
bq.  David
bq.  
bq.


                
> 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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