During import, single region blocks requests for >10 minutes, thread dumps, 
throws out pending requests, and continues
----------------------------------------------------------------------------------------------------------------------

                 Key: HBASE-790
                 URL: https://issues.apache.org/jira/browse/HBASE-790
             Project: Hadoop HBase
          Issue Type: Bug
          Components: regionserver
    Affects Versions: 0.2.0
         Environment: 11 node cluster.  1 master w/ namenodes and hmaster.  10 
slaves w/ datanodes and regionservers.  All are 2GHz quad core xeons, 4gb ram, 
raid 0.
            Reporter: Jonathan Gray
             Fix For: 0.2.0


During a batch import, I have two processes importing into a single region.

The behavior I saw was a regionserver with 2 regions of the table in question 
on it.  The first region split, and the new regions were reassigned to another 
regionserver.

Following that, inserting into the region that was left over began to block 
client requests.  I am attaching the regionserver log; below is the specific 
problem area:

2008-07-31 15:38:24,190 DEBUG 
org.apache.hadoop.hbase.client.HConnectionManager$TableServers: Cache hit in 
table locations for row <> and tableName .META.: location server 
72.34.249.217:60020, location region name .META.,,1
2008-07-31 15:38:24,194 INFO 
org.apache.hadoop.hbase.regionserver.CompactSplitThread: region split, META 
updated, and report to master all successful. Old region=REGION => {NAME => 
'items,01beddd6-813b-4f2b-ac48-a0cef395cb7e,12175434512
2008-07-31 15:38:34,052 INFO org.apache.hadoop.hbase.regionserver.HRegion: 
Blocking updates for 'IPC Server handler 7 on 60020' on region 
items,8001eb31-98bb-4087-bd8d-e4b42805addb,1217543451296: Memcache size 64.0m 
is >= than blocking
2008-07-31 15:39:00,270 INFO org.apache.hadoop.ipc.Server: IPC Server handler 8 
on 60020, call batchUpdate([EMAIL PROTECTED], row => 
02c241b4-9d32-452d-8dab-247f4af693eb, {column => content:title, value => '...', 
column => content:content, va
org.apache.hadoop.hbase.NotServingRegionException: 
items,01beddd6-813b-4f2b-ac48-a0cef395cb7e,1217543451296
        at 
org.apache.hadoop.hbase.regionserver.HRegionServer.getRegion(HRegionServer.java:1436)
        at 
org.apache.hadoop.hbase.regionserver.HRegionServer.batchUpdate(HRegionServer.java:1147)
        at sun.reflect.GeneratedMethodAccessor12.invoke(Unknown Source)
        at 
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:616)
        at org.apache.hadoop.hbase.ipc.HbaseRPC$Server.call(HbaseRPC.java:473)
        at org.apache.hadoop.ipc.Server$Handler.run(Server.java:896)
2008-07-31 15:39:09,547 INFO org.apache.hadoop.hbase.regionserver.HRegion: 
Blocking updates for 'IPC Server handler 8 on 60020' on region 
items,8001eb31-98bb-4087-bd8d-e4b42805addb,1217543451296: Memcache size 64.0m 
is >= than blocking
2008-07-31 15:39:44,079 INFO org.apache.hadoop.hbase.regionserver.HRegion: 
Blocking updates for 'IPC Server handler 9 on 60020' on region 
items,8001eb31-98bb-4087-bd8d-e4b42805addb,1217543451296: Memcache size 64.0m 
is >= than blocking
2008-07-31 15:40:19,574 INFO org.apache.hadoop.hbase.regionserver.HRegion: 
Blocking updates for 'IPC Server handler 1 on 60020' on region 
items,8001eb31-98bb-4087-bd8d-e4b42805addb,1217543451296: Memcache size 64.0m 
is >= than blocking
2008-07-31 15:49:09,130 INFO org.apache.hadoop.hbase.regionserver.LogRoller: 
Rolling hlog. Number of entries: 1
2008-07-31 15:49:09,144 DEBUG org.apache.hadoop.hbase.regionserver.HLog: 
Closing current log writer 
/hbase/log_72.34.249.212_1217535541159_60020/hlog.dat.1217543884691
2008-07-31 15:49:09,146 INFO org.apache.hadoop.hbase.regionserver.HLog: New log 
writer created at 
/hbase/log_72.34.249.212_1217535541159_60020/hlog.dat.1217544549145
2008-07-31 16:03:09,060 DEBUG org.apache.hadoop.hbase.regionserver.HRegion: 
Started memcache flush for region 
items,8001eb31-98bb-4087-bd8d-e4b42805addb,1217543451296. Current region 
memcache size 64.0m
2008-07-31 16:03:09,467 INFO org.apache.hadoop.hbase.regionserver.HRegion: 
Unblocking updates for region 
items,8001eb31-98bb-4087-bd8d-e4b42805addb,1217543451296 'IPC Server handler 5 
on 60020'
2008-07-31 16:03:09,478 INFO org.apache.hadoop.ipc.Server: Process Thread Dump: 
Discarding call batchUpdate([EMAIL PROTECTED], row => 
c08408b4-b68c-433c-ba3f-d46d3ba73288, {column => content:title, value => '...', 
column => content:content, v


As you can see there was a 14 minute delay between updates being blocked, and 
the unblocking occurring.

All the pending batchUpdates were thrown out (too old) and then importing 
proceeded normally.

The same behavior repeated itself later on a different regionserver, and again 
after a while it unfroze, kicked out pending updates, and continued.

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