Description
This is in reference to the mail sent in the dev mailing list
"Closed parent region present in Hlog.lastSeqWritten".
The sceanrio described is
We had a region that was split into two daughters. When the hlog roll tried to flush the region there was an entry in the HLog.lastSeqWritten that was not flushed or removed from the lastSeqWritten during the parent close.
Because this flush was not happening subsequent flushes were getting blocked
05:06:44,422 INFO org.apache.hadoop.hbase.regionserver.wal.HLog: Too many hlogs: logs=122, maxlogs=32; forcing flush of 1 regions(s): 2acaf8e3acfd2e8a5825a1f6f0aca4a8 05:06:44,422 WARN org.apache.hadoop.hbase.regionserver.LogRoller: Failed to schedule flush of 2acaf8e3acfd2e8a5825a1f6f0aca4a8r=null, requester=null 05:10:48,666 INFO org.apache.hadoop.hbase.regionserver.wal.HLog: Too many hlogs: logs=123, maxlogs=32; forcing flush of 1 regions(s): 2acaf8e3acfd2e8a5825a1f6f0aca4a8 05:10:48,666 WARN org.apache.hadoop.hbase.regionserver.LogRoller: Failed to schedule flush of 2acaf8e3acfd2e8a5825a1f6f0aca4a8r=null, requester=null 05:14:46,075 INFO org.apache.hadoop.hbase.regionserver.wal.HLog: Too many hlogs: logs=124, maxlogs=32; forcing flush of 1 regions(s): 2acaf8e3acfd2e8a5825a1f6f0aca4a8 05:14:46,075 WARN org.apache.hadoop.hbase.regionserver.LogRoller: Failed to schedule flush of 2acaf8e3acfd2e8a5825a1f6f0aca4a8r=null, requester=null 05:15:41,584 INFO org.apache.hadoop.hbase.regionserver.wal.HLog: Too many hlogs: logs=125, maxlogs=32; forcing flush of 1 regions(s): 2acaf8e3acfd2e8a5825a1f6f0aca4a8 05:15:41,584 WARN org.apache.hadoop.hbase.regionserver.LogRoller: Failed to schedule flush of 2acaf8e3acfd2e8a5825a1f6f0aca4a8r=null,
Lets see what happened for the region 2acaf8e3acfd2e8a5825a1f6f0aca4a8
2012-01-06 00:30:55,214 INFO org.apache.hadoop.hbase.regionserver.Store: Renaming flushed file at hdfs://192.168.1.103:9000/hbase/Htable_UFDR_031/2acaf8e3acfd2e8a5825a1f6f0aca4a8/.tmp/1755862026714756815 to hdfs://192.168.1.103:9000/hbase/Htable_UFDR_031/2acaf8e3acfd2e8a5825a1f6f0aca4a8/value/973789709483406123 2012-01-06 00:30:58,946 DEBUG org.apache.hadoop.hbase.regionserver.HRegion: Instantiated Htable_UFDR_016,049790700093168-04565200000,1325809837958.0ebe5bd7fcbc09ee074d5600b9d4e062. 2012-01-06 00:30:59,614 INFO org.apache.hadoop.hbase.regionserver.Store: Added hdfs://192.168.1.103:9000/hbase/Htable_UFDR_031/2acaf8e3acfd2e8a5825a1f6f0aca4a8/value/973789709483406123, entries=7537, sequenceid=20312223, memsize=4.2m, filesize=2.9m 2012-01-06 00:30:59,787 DEBUG org.apache.hadoop.hbase.regionserver.HRegion: Finished snapshotting, commencing flushing stores 2012-01-06 00:30:59,787 INFO org.apache.hadoop.hbase.regionserver.HRegion: Finished memstore flush of ~133.5m for region Htable_UFDR_031,00332,1325808823997.2acaf8e3acfd2e8a5825a1f6f0aca4a8. in 21816ms, sequenceid=20312223, compaction requested=true 2012-01-06 00:30:59,787 DEBUG org.apache.hadoop.hbase.regionserver.CompactSplitThread: Compaction requested for Htable_UFDR_031,00332,1325808823997.2acaf8e3acfd2e8a5825a1f6f0aca4a8. because regionserver20020.cacheFlusher; priority=0, compaction queue size=5840
A user triggered split has been issued to this region which can be seen in the above logs.
The flushing of this region has resulted in a seq id 20312223.
The region has been splitted and the parent region has been closed
00:31:12,607 INFO org.apache.hadoop.hbase.regionserver.SplitTransaction: Starting split of region Htable_UFDR_031,00332,1325808823997.2acaf8e3acfd2e8a5825a1f6f0aca4a8. 00:31:13,694 DEBUG org.apache.hadoop.hbase.regionserver.HRegion: Closing Htable_UFDR_031,00332,1325808823997.2acaf8e3acfd2e8a5825a1f6f0aca4a8.: disabling compactions & flushes 00:31:13,694 DEBUG org.apache.hadoop.hbase.regionserver.HRegion: Updates disabled for region Htable_UFDR_031,00332,1325808823997.2acaf8e3acfd2e8a5825a1f6f0aca4a8. 00:31:13,718 INFO org.apache.hadoop.hbase.regionserver.HRegion: Closed Htable_UFDR_031,00332,1325808823997.2acaf8e3acfd2e8a5825a1f6f0aca4a8. 00:31:39,552 INFO org.apache.hadoop.hbase.catalog.MetaEditor: Offlined parent region Htable_UFDR_031,00332,1325808823997.2acaf8e3acfd2e8a5825a1f6f0aca4a8. in META 00:31:41,374 DEBUG org.apache.hadoop.hbase.regionserver.Store: loaded hdfs://192.168.1.103:9000/hbase/Htable_UFDR_031/259d0c620c9105928e52713f4a5a252e/value/239119195230239381.2acaf8e3acfd2e8a5825a1f6f0aca4a8, isReference=true, isBulkLoadResult=false, seqid=20201181, majorCompaction=false 2012-01-06 00:31:42,529 DEBUG org.apache.hadoop.hbase.regionserver.Store: loaded hdfs://192.168.1.103:9000/hbase/Htable_UFDR_031/52ff3c7c6df6e0337876bbca29cee84a/value/973789709483406123.2acaf8e3acfd2e8a5825a1f6f0aca4a8, isReference=true, isBulkLoadResult=false, seqid=20312224, majorCompaction=false 2012-01-06 00:31:42,532 DEBUG org.apache.hadoop.hbase.regionserver.Store: loaded hdfs://192.168.1.103:9000/hbase/Htable_UFDR_031/259d0c620c9105928e52713f4a5a252e/value/973789709483406123.2acaf8e3acfd2e8a5825a1f6f0aca4a8, isReference=true, isBulkLoadResult=false, seqid=20312223, majorCompaction=false INFO org.apache.hadoop.hbase.regionserver.CompactSplitThread: Region split, META updated, and report to master. Parent=Htable_UFDR_031,00332,1325808823997.2acaf8e3acfd2e8a5825a1f6f0aca4a8., new regions: Htable_UFDR_031,00332,1325809872607.259d0c620c9105928e52713f4a5a252e., Htable_UFDR_031,003732800093168-03594291912,1325809872607.52ff3c7c6df6e0337876bbca29cee84a.. Split took 29sec
In the above logs we can also see that the new daugher regions have the next seq id as 20312223 and 20312224.
DEBUG org.apache.hadoop.hbase.regionserver.wal.HLog: Found 1 hlogs to remove out of total 4; oldest outstanding sequenceid is 20312224 from region 2acaf8e3acfd2e8a5825a1f6f0aca4a8
Now we see that the parent region which was clsoed has a seq id 20312224 which is not flushed.
So further flush are failing as the region is already removed from onlineRegionList.
The doubt here is before the region could be closed, a put has arrived for this region. But due to some reason the flush has not happened for that. We tried to dig this, but not able to get this problem again.
0.90.5 version + few 0.90.6 patches ( before 0.90.6RC0)
Attachments
Issue Links
- relates to
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HBASE-5568 Multi concurrent flushcache() for one region could cause data loss
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- Closed
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