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From Shahab Yunus <shahab.yu...@gmail.com>
Subject Re: Forcibly merging regions
Date Fri, 14 Nov 2014 17:48:37 GMT
I just checked. No snapshots were taken and 'list_snapshots' also returns
nothing.

Regards,
Shahab

On Fri, Nov 14, 2014 at 12:39 PM, Shahab Yunus <shahab.yunus@gmail.com>
wrote:

> No. Not that I can recall but I can check.
>
> From resolution perspective, is there any way we can resolve this. More
> importantly, anyway we can automate the resolution, if we run into such
> issues in future? 'Cleaning the qualifier', that is.
>
> Regards,
> Shahab
>
> On Fri, Nov 14, 2014 at 12:12 PM, Ted Yu <yuzhihong@gmail.com> wrote:
>
>> One possibility was that region 7373f75181c71eb5061a6673cee15931 was
>> involved in some hbase snapshot.
>>
>> Was the underlying table being snapshotted in recent past ?
>>
>> Cheers
>>
>> On Fri, Nov 14, 2014 at 9:05 AM, Shahab Yunus <shahab.yunus@gmail.com>
>> wrote:
>>
>> > Thanks again.
>> >
>> > But I have been polling for a while and it still doesn't merge. I mean
>> this
>> > particular region example that I sent you, I am trying to merge it since
>> > yesterday. I ran the polling-base code all night and I have to kill it.
>> > Then in the morning, I tried manual merging through hbase shell and it
>> > still doesn't merge. Note that the current polling logic doesnot try to
>> > call merge again. It just checks the region size.
>> >
>> > So how to clean it then? Or actually make it merge? Plus is this
>> something
>> > expected (a region keeping a reference)? How can we avoid it?
>> >
>> > Note that this is not limited to this table only. We are seeing this in
>> > other regions of other tables as well. Are we merging too fast?
>> >
>> >
>> >
>> > Regards,
>> > Shahab
>> >
>> > On Fri, Nov 14, 2014 at 11:58 AM, Ted Yu <yuzhihong@gmail.com> wrote:
>> >
>> > > Polling as you described is fine.
>> > >
>> > > catalogJanitor.cleanMergeQualifier() is called by
>> > > DispatchMergingRegionHandler.
>> > >
>> > > If clean was successful, you would see the following:
>> > >
>> > >       LOG.debug("Deleting region " + regionA.getRegionNameAsString()
>> + "
>> > > and "
>> > >
>> > >           + regionB.getRegionNameAsString()
>> > >
>> > >           + " from fs because merged region no longer holds
>> references");
>> > >
>> > > Assuming there was no log below in your master log:
>> > >
>> > >       LOG.error("Merged region " + region.getRegionNameAsString()
>> > >
>> > >           + " has only one merge qualifier in META.");
>> > >
>> > > It would be the case that 7373f75181c71eb5061a6673cee15931 still had
>> > > reference file.
>> > >
>> > > Cheers
>> > >
>> > > On Fri, Nov 14, 2014 at 8:35 AM, Shahab Yunus <shahab.yunus@gmail.com
>> >
>> > > wrote:
>> > >
>> > > > Hi Ted.
>> > > >
>> > > > The log bit is below at the end of the email. This is the command
to
>> > > merge
>> > > > that I gave just now through hbase shell. forcible was false but it
>> > > behaves
>> > > > similarly if forcible is true too. This is from master log. Indeed
>> the
>> > > > region merging was skipped! What does this mean? Data seems to be
>> > intact
>> > > > for this table.
>> > > >
>> > > > Just to give you a background. This table was first merge by the
>> auto
>> > > mated
>> > > > java application. What we are doing is that we are merging tables
>> > > > programmatically. As the HBaseAdmin.mergeRegions calls i async, we
>> poll
>> > > for
>> > > > the number of regions getting lowered after this merge call. The
>> > > > application hangs and continues polling for ever as the previous
>> merge
>> > > > didn't happen.
>> > > >
>> > > > In this poll loop, we do get the number of regions by a fresh call
>> to
>> > > > HBaseAdmin.getTableRegions(tableName).getSize().
>> > > >
>> > > > What are these merge qualifiers and what are we doing wrong or
>> should
>> > do?
>> > > >
>> > > > In the polling loop we can somehow retry merge again? But how can
we
>> > > know,
>> > > > that we need to call merge again as it works for some regions. Is
>> the
>> > > table
>> > > > meta corrupted for some reason by the above logic?
>> > > >
>> > > > Thanks a lot.
>> > > >
>> > > >
>> > > >
>> > > >
>> > ------------------------------------------------------------------------
>> > > >
>> > > > 2014-11-14 11:25:02,643 INFO org.apache.zookeeper.ZooKeeper:
>> Session:
>> > > > 0x348c7017707236b closed
>> > > > 2014-11-14 11:25:02,643 INFO org.apache.zookeeper.ClientCnxn:
>> > EventThread
>> > > > shut down
>> > > > 2014-11-14 11:25:02,645 INFO org.apache.zookeeper.ZooKeeper:
>> Initiating
>> > > > client connection,
>> > > >
>> > > >
>> > >
>> >
>> connectString=ip-1010019.ec2.internal:2181,ip-1010017.ec2.internal:2181,ip-1010018.ec2.internal:2181
>> > > > sessionTimeout=60000
>> watcher=catalogtracker-on-hconnection-0x47d865f2,
>> > > >
>> > > >
>> > >
>> >
>> quorum=ip-1010019.ec2.internal:2181,ip-1010017.ec2.internal:2181,ip-1010018.ec2.internal:2181,
>> > > > baseZNode=/hbase
>> > > > 2014-11-14 11:25:02,645 INFO
>> > > > org.apache.hadoop.hbase.zookeeper.RecoverableZooKeeper: Process
>> > > > identifier=catalogtracker-on-hconnection-0x47d865f2 connecting to
>> > > ZooKeeper
>> > > >
>> > > >
>> > >
>> >
>> ensemble=ip-1010019.ec2.internal:2181,ip-1010017.ec2.internal:2181,ip-1010018.ec2.internal:2181
>> > > > 2014-11-14 11:25:02,645 INFO org.apache.zookeeper.ClientCnxn:
>> Opening
>> > > > socket connection to server ip-1010018.ec2.internal/1010019:2181.
>> Will
>> > > not
>> > > > attempt to authenticate using SASL (unknown error)
>> > > > 2014-11-14 11:25:02,646 INFO org.apache.zookeeper.ClientCnxn: Socket
>> > > > connection established to ip-1010018.ec2.internal/1010019:2181,
>> > > initiating
>> > > > session
>> > > > 2014-11-14 11:25:02,648 INFO org.apache.zookeeper.ClientCnxn:
>> Session
>> > > > establishment complete on server
>> ip-1010018.ec2.internal/1010019:2181,
>> > > > sessionid = 0x348c7017707236c, negotiated timeout = 60000
>> > > > 2014-11-14 11:25:02,703 INFO org.apache.zookeeper.ZooKeeper:
>> Session:
>> > > > 0x348c7017707236c closed
>> > > > 2014-11-14 11:25:02,703 INFO org.apache.zookeeper.ClientCnxn:
>> > EventThread
>> > > > shut down
>> > > > 2014-11-14 11:25:30,713 INFO
>> > > > org.apache.hadoop.hbase.master.handler.DispatchMergingRegionHandler:
>> > Skip
>> > > > merging regions
>> > > > TABLE_NAME,,1415915112497.7373f75181c71eb5061a6673cee15931.,
>> > > >
>> > > >
>> > >
>> >
>> TABLE_NAME,\x02\xFA\xF0\x80\x00\x00\x01I\xAA\xD5\x87\xA8\x19\x99\x99\x99\x99\x99\x99\x90,1415910559217.43f4d3685d113d3ae18eea9f189de096.,
>> > > > because region 7373f75181c71eb5061a6673cee15931 has merge qualifier
>> > > > 2014-11-14 11:25:41,383 INFO org.apache.zookeeper.ZooKeeper:
>> Initiating
>> > > > client connection,
>> > > >
>> > > >
>> > >
>> >
>> connectString=ip-1010019.ec2.internal:2181,ip-1010017.ec2.internal:2181,ip-1010018.ec2.internal:2181
>> > > > sessionTimeout=60000
>> watcher=catalogtracker-on-hconnection-0x47d865f2,
>> > > >
>> > > >
>> > >
>> >
>> quorum=ip-1010019.ec2.internal:2181,ip-1010017.ec2.internal:2181,ip-1010018.ec2.internal:2181,
>> > > > baseZNode=/hbase
>> > > > 2014-11-14 11:25:41,384 INFO
>> > > > org.apache.hadoop.hbase.zookeeper.RecoverableZooKeeper: Process
>> > > > identifier=catalogtracker-on-hconnection-0x47d865f2 connecting to
>> > > ZooKeeper
>> > > >
>> > > >
>> > >
>> >
>> ensemble=ip-1010019.ec2.internal:2181,ip-1010017.ec2.internal:2181,ip-1010018.ec2.internal:2181
>> > > > 2014-11-14 11:25:41,384 INFO org.apache.zookeeper.ClientCnxn:
>> Opening
>> > > > socket connection to server ip-1010018.ec2.internal/1010019:2181.
>> Will
>> > > not
>> > > > attempt to authenticate using SASL (unknown error)
>> > > > 2014-11-14 11:25:41,386 INFO org.apache.zookeeper.ClientCnxn: Socket
>> > > > connection established to ip-1010018.ec2.internal/1010019:2181,
>> > > initiating
>> > > > session
>> > > > 2014-11-14 11:25:41,389 INFO org.apache.zookeeper.ClientCnxn:
>> Session
>> > > > establishment complete on server
>> ip-1010018.ec2.internal/1010019:2181,
>> > > > sessionid = 0x348c7017707236e, negotiated timeout = 60000
>> > > > 2014-11-14 11:25:41,397 INFO org.apache.zookeeper.ZooKeeper:
>> Session:
>> > > > 0x348c7017707236e closed
>> > > > 2014-11-14 11:25:41,398 INFO org.apache.zookeeper.ClientCnxn:
>> > EventThread
>> > > > shut down
>> > > >
>> > > >
>> > >
>> >
>> ------------------------------------------------------------------------------------------------------------------------------------
>> > > >
>> > > > Regards,
>> > > > Shahab
>> > > >
>> > > > On Fri, Nov 14, 2014 at 10:56 AM, Ted Yu <yuzhihong@gmail.com>
>> wrote:
>> > > >
>> > > > > Looking at DispatchMergingRegionHandler, it does some check before
>> > > > > initiating the merge.
>> > > > > e.g.:
>> > > > >
>> > > > >       LOG.info("Skip merging regions " +
>> > > region_a.getRegionNameAsString()
>> > > > >
>> > > > >           + ", " + region_b.getRegionNameAsString() + ", because
>> > > region "
>> > > > >
>> > > > >           + (regionAHasMergeQualifier ? region_a.getEncodedName()
>> :
>> > > > > region_b
>> > > > >
>> > > > >               .getEncodedName()) + " has merge qualifier");
>> > > > >
>> > > > > Can you take a look at master log around the time merge request
>> was
>> > > > issued
>> > > > > to see if you can get some clue ?
>> > > > >
>> > > > > Cheers
>> > > > >
>> > > > > On Fri, Nov 14, 2014 at 6:41 AM, Shahab Yunus <
>> > shahab.yunus@gmail.com>
>> > > > > wrote:
>> > > > >
>> > > > > > The documentation of online merge tool (merge_region) states
>> that
>> > if
>> > > we
>> > > > > > forcibly merge regions (by setting the 3rd attribute as
true)
>> then
>> > it
>> > > > can
>> > > > > > create overlapping regions. if this happens then will this
>> render
>> > the
>> > > > > > region or table unusable or it is just a performance hit?
I mean
>> > how
>> > > > > bigger
>> > > > > > of a deal it is?
>> > > > > >
>> > > > > > Actually, we are merging regions using the programmatic
API for
>> > this
>> > > > and
>> > > > > > setting this flag ('forcible') as false. But for some tables
(we
>> > > > haven't
>> > > > > > figured out a pattern yet, data is still accessible), merge
of
>> > > regions
>> > > > do
>> > > > > > not happen at all. Afterwards we tried with this flag =
true,
>> and
>> > it
>> > > > > still
>> > > > > > doesn't merge them.
>> > > > > >
>> > > > > > CDH 5.1.0
>> > > > > > (Hbase is 0.98.1-cdh5.1.0)
>> > > > > >
>> > > > > > Regards,
>> > > > > > Shahab
>> > > > > >
>> > > > >
>> > > >
>> > >
>> >
>>
>
>

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