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Date: Sat, 10 Mar 2012 00:42:58 +0000 (UTC)
From: "jiraposter@reviews.apache.org (Commented) (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (HBASE-5209) HConnection/HMasterInterface should
 allow for way to get hostname of currently active master in multi-master
 HBase setup
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    [ https://issues.apache.org/jira/browse/HBASE-5209?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13226641#comment-13226641 ] 

jiraposter@reviews.apache.org commented on HBASE-5209:
------------------------------------------------------


bq.  On 2012-03-10 00:35:03, Michael Stack wrote:
bq.  > lgtm

I didn't actually submit my updated patch yet in response to Jon's comments.  :D  I will soon.


bq.  On 2012-03-10 00:35:03, Michael Stack wrote:
bq.  > src/main/java/org/apache/hadoop/hbase/ClusterStatus.java, line 227
bq.  > <https://reviews.apache.org/r/3892/diff/3/?file=75401#file75401line227>
bq.  >
bq.  >     This method seems a little superfluous

I wanted to stay consistent with the other accessor APIs in this class that operated on similar lists.


bq.  On 2012-03-10 00:35:03, Michael Stack wrote:
bq.  > src/main/java/org/apache/hadoop/hbase/master/HMaster.java, line 1396
bq.  > <https://reviews.apache.org/r/3892/diff/3/?file=75403#file75403line1396>
bq.  >
bq.  >     Should we be writing the master name by doing ServerName#getVersionedBytes and then parseVersionedServerName

I can do this.


- David


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On 2012-02-16 06:30:31, 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 2012-02-16 06:30:31)
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 hbck -details - 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.  * Tested build with this diff vs. build without this diff, in all combinations of client and server
bq.    * Verified that new client can run against old servers without incident and with the defaults applied.
bq.    * Note that old clients get an error when running against new servers, because the old readFields() code in ClusterStatus does not handle exceptions of any kind.  This is not solvable, at least in the scope of this change.
bq.  
bq.  12/02/15 15:15:38 INFO zookeeper.ClientCnxn: Session establishment complete on server haus02.sf.cloudera.com/172.29.5.33:30181, sessionid = 0x135834c75e20008, negotiated timeout = 5000
bq.  12/02/15 15:15:39 ERROR io.HbaseObjectWritable: Error in readFields
bq.  A record version mismatch occured. Expecting v2, found v3
bq.          at org.apache.hadoop.io.VersionedWritable.readFields(VersionedWritable.java:46)
bq.          at org.apache.hadoop.hbase.ClusterStatus.readFields(ClusterStatus.java:247)
bq.          at org.apache.hadoop.hbase.io.HbaseObjectWritable.readObject(HbaseObjectWritable.java:583)
bq.          at org.apache.hadoop.hbase.io.HbaseObjectWritable.readFields(HbaseObjectWritable.java:297)
bq.  
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: 0.90.5, 0.92.0, 0.94.0
>            Reporter: Aditya Acharya
>            Assignee: David S. Wang
>             Fix For: 0.92.1, 0.94.0
>
>         Attachments: 5209.addendum, HBASE_5209_v5.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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