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From "Jieshan Bean (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-4095) Hlog may not be rolled in a long time if checkLowReplication's request of LogRoll is blocked
Date Mon, 08 Aug 2011 03:41:27 GMT

     [ https://issues.apache.org/jira/browse/HBASE-4095?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jieshan Bean updated HBASE-4095:
--------------------------------

    Attachment: HBase-4095-V5-Branch.patch

@Ted,
{noformat}
But the rollWriter was able to executed in time. So the following roll-requests were skippted.

I think you meant:
But the rollWriter wasn't able to execute in time. And the following roll-requests were skipped.
{noformat}
Yes, you're right. Sorry:(

@ramkrishna,
There's several possibilities of "why did rollWriter not executed in time". It may not get
the lock of "cacheFlushLock". The patch has taken care of it. 
If one request of rollWriter got blocked(was not allowed to hold cacheFlushLock), it will
not effect the following requests.
There's 3 scenarios of request rollWriter:
1. Periodic execution.
2. Current Hlog writer has larger than 256M(It's a configurable parameter).
3. Current Hlog replicas is less than the initial replicas.

The patch of "disable the rolling-request" is just disable the request from scenario 3.
We needn't expose the new properties in hbase-default.xml, for they have the default value.


> Hlog may not be rolled in a long time if checkLowReplication's request of LogRoll is
blocked
> --------------------------------------------------------------------------------------------
>
>                 Key: HBASE-4095
>                 URL: https://issues.apache.org/jira/browse/HBASE-4095
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver
>    Affects Versions: 0.90.3
>            Reporter: Jieshan Bean
>            Assignee: Jieshan Bean
>         Attachments: HBASE-4095-90-v2.patch, HBASE-4095-90.patch, HBASE-4095-trunk-v2.patch,
HBASE-4095-trunk.patch, HBase-4095-V4-Branch.patch, HBase-4095-V5-Branch.patch, HlogFileIsVeryLarge.gif,
RelatedLogs2011-07-28.txt, TestResultForPatch-V4.rar, hbase-root-regionserver-193-195-5-111.rar,
surefire-report-branch.html
>
>
> Some large Hlog files(Larger than 10G) appeared in our environment, and I got the reason
why they got so huge:
> 1. The replicas is less than the expect number. So the method of checkLowReplication
will be called each sync.
> 2. The method checkLowReplication request log-roll first, and set logRollRequested as
true: 
> {noformat}
> private void checkLowReplication() {
> // if the number of replicas in HDFS has fallen below the initial
> // value, then roll logs.
> try {
>   int numCurrentReplicas = getLogReplication();
>   if (numCurrentReplicas != 0 &&
> 	  numCurrentReplicas < this.initialReplication) {
> 	LOG.warn("HDFS pipeline error detected. " +
> 		"Found " + numCurrentReplicas + " replicas but expecting " +
> 		this.initialReplication + " replicas. " +
> 		" Requesting close of hlog.");
> 	requestLogRoll();
> 	logRollRequested = true;
>   }
> } catch (Exception e) {
>   LOG.warn("Unable to invoke DFSOutputStream.getNumCurrentReplicas" + e +
> 	  " still proceeding ahead...");
> }
> }
> {noformat}
> 3.requestLogRoll() just commit the roll request. It may not execute in time, for it must
got the un-fair lock of cacheFlushLock.
> But the lock may be carried by the cacheflush threads.
> 4.logRollRequested was true until the log-roll executed. So during the time, each request
of log-roll in sync() was skipped.
> Here's the logs while the problem happened(Please notice the file size of hlog "193-195-5-111%3A20020.1309937386639"
in the last row):
> 2011-07-06 15:28:59,284 WARN org.apache.hadoop.hbase.regionserver.wal.HLog: HDFS pipeline
error detected. Found 2 replicas but expecting 3 replicas.  Requesting close of hlog.
> 2011-07-06 15:29:46,714 INFO org.apache.hadoop.hbase.regionserver.wal.HLog: Roll /hbase/.logs/193-195-5-111,20020,1309922880081/193-195-5-111%3A20020.1309937339119,
entries=32434, filesize=239589754. New hlog /hbase/.logs/193-195-5-111,20020,1309922880081/193-195-5-111%3A20020.1309937386639
> 2011-07-06 15:29:56,929 WARN org.apache.hadoop.hbase.regionserver.wal.HLog: HDFS pipeline
error detected. Found 2 replicas but expecting 3 replicas.  Requesting close of hlog.
> 2011-07-06 15:29:56,933 INFO org.apache.hadoop.hbase.regionserver.Store: Renaming flushed
file at hdfs://193.195.5.112:9000/hbase/Htable_UFDR_034/a3780cf0c909d8cf8f8ed618b290cc95/.tmp/4656903854447026847
to hdfs://193.195.5.112:9000/hbase/Htable_UFDR_034/a3780cf0c909d8cf8f8ed618b290cc95/value/8603005630220380983
> 2011-07-06 15:29:57,391 INFO org.apache.hadoop.hbase.regionserver.Store: Added hdfs://193.195.5.112:9000/hbase/Htable_UFDR_034/a3780cf0c909d8cf8f8ed618b290cc95/value/8603005630220380983,
entries=445880, sequenceid=248900, memsize=207.5m, filesize=130.1m
> 2011-07-06 15:29:57,478 INFO org.apache.hadoop.hbase.regionserver.HRegion: Finished memstore
flush of ~207.5m for region Htable_UFDR_034,07664,1309936974158.a3780cf0c909d8cf8f8ed618b290cc95.
in 10839ms, sequenceid=248900, compaction requested=false
> 2011-07-06 15:28:59,236 INFO org.apache.hadoop.hbase.regionserver.wal.HLog: Roll /hbase/.logs/193-195-5-111,20020,1309922880081/193-195-5-111%3A20020.1309926531955,
entries=216459, filesize=2370387468. New hlog /hbase/.logs/193-195-5-111,20020,1309922880081/193-195-5-111%3A20020.1309937339119
> 2011-07-06 15:29:46,714 INFO org.apache.hadoop.hbase.regionserver.wal.HLog: Roll /hbase/.logs/193-195-5-111,20020,1309922880081/193-195-5-111%3A20020.1309937339119,
entries=32434, filesize=239589754. New hlog /hbase/.logs/193-195-5-111,20020,1309922880081/193-195-5-111%3A20020.1309937386639
> 2011-07-06 16:29:58,775 DEBUG org.apache.hadoop.hbase.regionserver.LogRoller: Hlog roll
period 3600000ms elapsed
> 2011-07-06 16:29:58,775 DEBUG org.apache.hadoop.hbase.regionserver.LogRoller: Hlog roll
period 3600000ms elapsed
> 2011-07-06 16:30:01,978 INFO org.apache.hadoop.hbase.regionserver.wal.HLog: Roll /hbase/.logs/193-195-5-111,20020,1309922880081/193-195-5-111%3A20020.1309937386639,
entries=1135576, filesize=19220372830. New hlog /hbase/.logs/193-195-5-111,20020,1309922880081/193-195-5-111%3A20020.1309940998890

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