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From "jiraposter@reviews.apache.org (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4455) Rolling restart RSs scenario, -ROOT-, .META. regions are lost in AssignmentManager
Date Fri, 23 Sep 2011 08:18:28 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13113248#comment-13113248
] 

jiraposter@reviews.apache.org commented on HBASE-4455:
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Great stuff!  I have some questions throughout but seems like this will make everything more
resilient to root/meta servers failing.  Is the general approach to always verify / always
check rather than relying on cached locations or values?

Have you thought about any ways that we could add some better unit tests around this stuff?
 There's a TestRollingRestart that is obviously not good enough :)


http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/catalog/CatalogTracker.java
<https://reviews.apache.org/r/2007/#comment4598>

    so we always verify the connection now?



http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/catalog/CatalogTracker.java
<https://reviews.apache.org/r/2007/#comment4597>

    why log the cached META server here?  didn't we just verify that it was not valid?



http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/catalog/CatalogTracker.java
<https://reviews.apache.org/r/2007/#comment4599>

    why log the cached meta location here?  it might be confusing since it doesn't log that
we just found this meta location was invalid



http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/catalog/CatalogTracker.java
<https://reviews.apache.org/r/2007/#comment4601>

    nice catch



http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/catalog/CatalogTracker.java
<https://reviews.apache.org/r/2007/#comment4602>

    why do we have two hard-coded timeouts in this area of code? :)
    
    this code seems to always sleep 500ms at a time unless you set timeout=0 and then it loops
every 50ms?  that doesn't seem right... i could set timeout to 100ms and it would sleep 500ms.
 sleeping 50ms every time would be better but there's probably a solution with less overhead
(doing remote read queries every 50ms in a loop)
    
    could we just notifyAll() on metaAvailable whenever we relocate root?



http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/catalog/CatalogTracker.java
<https://reviews.apache.org/r/2007/#comment4603>

    good



http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/master/AssignmentManager.java
<https://reviews.apache.org/r/2007/#comment4604>

    add another * here, so: /**
    
    that ensure this gets picked up as javadoc



http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/master/AssignmentManager.java
<https://reviews.apache.org/r/2007/#comment4605>

    what about this method is specific to the shutdown server?  this seems specific about
regions in transition.  if we only use it in the context of servers being shut down then maybe
name it accordingly?  it does seem like a generally useful method though and just related
to ZK (could put it in a ZK util class?)



http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/master/AssignmentManager.java
<https://reviews.apache.org/r/2007/#comment4606>

    this looks like a random debug statement, what does matchZK, sn: server mean?



http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/master/handler/ServerShutdownHandler.java
<https://reviews.apache.org/r/2007/#comment4607>

    i'm also a bit confused by this.  couldn't we just increase the thread pool size to 2?
:)



http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/regionserver/handler/CloseRegionHandler.java
<https://reviews.apache.org/r/2007/#comment4608>

    is this normal?  should it be a warn?  maybe a comment on why this would happen



http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/zookeeper/RootRegionTracker.java
<https://reviews.apache.org/r/2007/#comment4609>

    why this change?  should this be rolled into the ZKNodeTracker rather than overriding
the getData() behavior?



http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/zookeeper/RootRegionTracker.java
<https://reviews.apache.org/r/2007/#comment4610>

    it seems like you're covering up for bugs in the underlying ZKNodeTracker... can we fix
that instead?  or if it's a matter of returning a cached value or not, can we just add a boolean
flag for refresh/nocache?


- Jonathan


On 2011-09-23 00:15:11, Ming Ma wrote:
bq.  
bq.  -----------------------------------------------------------
bq.  This is an automatically generated e-mail. To reply, visit:
bq.  https://reviews.apache.org/r/2007/
bq.  -----------------------------------------------------------
bq.  
bq.  (Updated 2011-09-23 00:15:11)
bq.  
bq.  
bq.  Review request for hbase.
bq.  
bq.  
bq.  Summary
bq.  -------
bq.  
bq.  1. Add more logging.
bq.  2. Clean up CatalogTracker. waitForMeta waits for "timeout" value. When waitForMetaServerConnectionDefault
is called by MetaNodeTracker, the timeout value is large. So it doesn't retry in case .ROOT.
is updated; add the proper implementation for CatalogTracker.verifyMetaRegionLocation
bq.  4. Check for the latest -ROOT- and .META. region location during the handling of server
shutdown.
bq.  5. Right after assigning the -ROOT- or .META. in ServerShutdownHandler, don't block and
wait for .META. availability. Resubmit another ServerShutdownHandler for regular regions.
bq.  
bq.  
bq.  This addresses bug HBASE-4455.
bq.      https://issues.apache.org/jira/browse/HBASE-4455
bq.  
bq.  
bq.  Diffs
bq.  -----
bq.  
bq.    http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/catalog/CatalogTracker.java
1172205 
bq.    http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/master/AssignmentManager.java
1172205 
bq.    http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/master/ServerManager.java
1172205 
bq.    http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/master/handler/MetaServerShutdownHandler.java
1172205 
bq.    http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/master/handler/OpenedRegionHandler.java
1172205 
bq.    http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/master/handler/ServerShutdownHandler.java
1172205 
bq.    http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/regionserver/HRegionServer.java
1172205 
bq.    http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/regionserver/handler/CloseRegionHandler.java
1172205 
bq.    http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/regionserver/handler/OpenRegionHandler.java
1172205 
bq.    http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/zookeeper/MetaNodeTracker.java
1172205 
bq.    http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/zookeeper/RootRegionTracker.java
1172205 
bq.    http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/zookeeper/ZooKeeperNodeTracker.java
1172205 
bq.  
bq.  Diff: https://reviews.apache.org/r/2007/diff
bq.  
bq.  
bq.  Testing
bq.  -------
bq.  
bq.  Keep Master up all the time, do rolling restart of RSs like this - stop RS1, wait for
2 seconds, stop RS2, start RS1, wait for 2 seconds, stop RS3, start RS2, wait for 2 seconds,
etc. The program can run for couple hours until it stops. -ROOT- and .META. are available
during that time.
bq.  
bq.  
bq.  Thanks,
bq.  
bq.  Ming
bq.  
bq.



> Rolling restart RSs scenario, -ROOT-, .META. regions are lost in AssignmentManager
> ----------------------------------------------------------------------------------
>
>                 Key: HBASE-4455
>                 URL: https://issues.apache.org/jira/browse/HBASE-4455
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Ming Ma
>            Assignee: Ming Ma
>             Fix For: 0.92.0
>
>
> Keep Master up all the time, do rolling restart of RSs like this - stop RS1, wait for
2 seconds, stop RS2, start RS1, wait for 2 seconds, stop RS3, start RS2, wait for 2 seconds,
etc. After a while, you will find the -ROOT-, .META. regions aren't in "regions in transtion"
from AssignmentManager point of view, but they aren't assigned to any regions. Here are the
issues.
> 1. .-ROOT- or .META. location is stale when MetaServerShutdownHandler is invoked to check
if it contains -ROOT- region. That is due to long delay from ZK notification and async nature
of the system. Here is an example, even though new root region server sea-lab-1,60020,1316380133656
is set at T2, at T3 the shutdown process for sea-lab-1,60020,1316380133656, the root location
still points to old server sea-lab-3,60020,1316380037898.
> T1: 2011-09-18 14:08:52,470 DEBUG org.apache.hadoop.hbase.zookeeper.ZKUtil: master:6
> 0000-0x1327e43175e0000 Retrieved 29 byte(s) of data from znode /hbase/root-regio
> n-server and set watcher; sea-lab-3,60020,1316380037898
> T2: 2011-09-18 14:08:57,173 INFO org.apache.hadoop.hbase.catalog.RootLocationEditor:
Setting ROOT region location in ZooKeeper as sea-lab-1,60020,1316380133656
> T3: 2011-09-18 14:10:26,393 DEBUG org.apache.hadoop.hbase.master.ServerManager: Adde
> d=sea-lab-1,60020,1316380133656 to dead servers, submitted shutdown handler to be executed,
root=false, meta=true, current Root Location: sea-lab-3,60020,1316380037898
> T4: 2011-09-18 14:12:37,314 DEBUG org.apache.hadoop.hbase.zookeeper.ZKUtil: master:6
> 0000-0x1327e43175e0000 Retrieved 29 byte(s) of data from znode /hbase/root-region-server
and set watcher; sea-lab-1,60020,1316380133656
> 2. The MetaServerShutdownHandler worker thread that waits for -ROOT- or .META. availability
could be blocked. If meanwhile, the new server that -ROOT- or .META. is being assigned restarted,
another instance of MetaServerShutdownHandler is queued. Eventually, all MetaServerShutdownHandler
worker threads are filled up. It looks like HBASE-4245.

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