Updates to .META. blocked under high MemStore load
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Key: HBASE-2018
URL: https://issues.apache.org/jira/browse/HBASE-2018
Project: Hadoop HBase
Issue Type: Bug
Affects Versions: 0.20.2
Reporter: Jean-Daniel Cryans
Assignee: Jean-Daniel Cryans
Priority: Blocker
Fix For: 0.20.3, 0.21.0
I discovered this on Lars' cluster. The symptom was the good old:
{code}
09/11/30 08:10:26 INFO mapred.JobClient: Task Id :
attempt_200911250121_0011_r_000010_1, Status : FAILED
org.apache.hadoop.hbase.client.RetriesExhaustedException: Trying to contact
region server Some server, retryOnlyOne=true, index=0, islastrow=false,
tries=9, numtries=10, i=14, listsize=20,
region=prev-docs,de68fb97795ef3d936a3f10ff8790253,1259573366564 for region
prev-docs,ccea967e66ccb53d83c48849c3a23f21,1259542138868, row
'ccff8cd4ca871c41f4fa7d44cffed962', but failed after 10 attempts.
Exceptions:
at
org.apache.hadoop.hbase.client.HConnectionManager$TableServers$Batch.process(HConnectionManager.java:1120)
at
org.apache.hadoop.hbase.client.HConnectionManager$TableServers.processBatchOfRows(HConnectionManager.java:1201)
at org.apache.hadoop.hbase.client.HTable.flushCommits(HTable.java:605)
at org.apache.hadoop.hbase.client.HTable.put(HTable.java:470)
at org.apache.hadoop.hbase.mapreduce.TableOutputFormat$TableRecordW
{code}
But the load wasn't that heavy, just lots of splitting going on. Looking at the
logs, I see a split taking more than 4 minutes which is explained by this
happening on the RS hosting .META. :
{code}
2009-11-30 08:08:39,922 INFO
org.apache.hadoop.hbase.regionserver.MemStoreFlusher: Forced flushing of
prev-docs,2c9d51e57b20decd5c6419d23ede822b,1259542273901 because global
memstore limit of 1.6g exceeded; currently 1.6g and flushing till 1021.9m
...
2009-11-30 08:12:33,743 DEBUG org.apache.hadoop.hbase.regionserver.HRegion:
Finished memstore flush of ~22.9m for region
prev-docs,c8fea4fbbc41e746d960854ed4d41dd6,1259587143838 in 14160ms, sequence
id=13677, compaction requested=false
2009-11-30 08:12:33,744 INFO
org.apache.hadoop.hbase.regionserver.MemStoreFlusher: Forced flushing of
prev-docs,39c2995d955c041d21f4dc4a0d0dbf6c,1259587061295 because global
memstore limit of 1.6g exceeded; currently 1.0g and flushing till 1021.9m
{code}
So we should not block updates to .META. for any reason. I'm pretty sure this
issue explains other issues we've seen on the mailing list.
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