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https://issues.apache.org/jira/browse/HBASE-7728?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13568490#comment-13568490
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Anoop Sam John commented on HBASE-7728:
---------------------------------------
[~yuzhih...@gmail.com] You mean this?
{code}
synchronized (this.updateLock) {
if (this.closed) return;
tempWriter = this.writer; // guaranteed non-null
}
{code}
Yes here we check for this.closed state. This well guards the tempWriter to be
not null during the 1st flush attempt.
I was wrong the above comment that we need null check.
But we need null check down the line when we do the sync() call on the writer?
{code}
try {
tempWriter.sync();
} catch(IOException io) {
synchronized (this.updateLock) {
// HBASE-4387, HBASE-5623, retry with updateLock held
tempWriter = this.writer;
tempWriter.sync();
}
}
{code}
Or instead of null checks all the places can we do this.closed checks?
Also in the log can we write that info that we will do a retry for the flush?
Do we need the log level to be error or WARN is fine? May be error also okey.
> deadlock occurs between hlog roller and hlog syncer
> ---------------------------------------------------
>
> Key: HBASE-7728
> URL: https://issues.apache.org/jira/browse/HBASE-7728
> Project: HBase
> Issue Type: Bug
> Components: wal
> Affects Versions: 0.94.2
> Environment: Linux 2.6.18-164.el5 x86_64 GNU/Linux
> Reporter: Wang Qiang
> Priority: Blocker
> Fix For: 0.96.0, 0.94.5
>
> Attachments: 7728-suggest-0.96.txt, 7728-suggest.txt, 7728-v1.txt,
> 7728-v2.txt, 7728-v3.txt
>
>
> the hlog roller thread and hlog syncer thread may occur dead lock with the
> 'flushLock' and 'updateLock', and then cause all 'IPC Server handler' thread
> blocked on hlog append. the jstack info is as follow :
> "regionserver60020.logRoller":
> at
> org.apache.hadoop.hbase.regionserver.wal.HLog.syncer(HLog.java:1305)
> - waiting to lock <0x000000067bf88d58> (a java.lang.Object)
> at
> org.apache.hadoop.hbase.regionserver.wal.HLog.syncer(HLog.java:1283)
> at org.apache.hadoop.hbase.regionserver.wal.HLog.sync(HLog.java:1456)
> at
> org.apache.hadoop.hbase.regionserver.wal.HLog.cleanupCurrentWriter(HLog.java:876)
> at
> org.apache.hadoop.hbase.regionserver.wal.HLog.rollWriter(HLog.java:657)
> - locked <0x000000067d54ace0> (a java.lang.Object)
> at
> org.apache.hadoop.hbase.regionserver.LogRoller.run(LogRoller.java:94)
> at java.lang.Thread.run(Thread.java:662)
> "regionserver60020.logSyncer":
> at
> org.apache.hadoop.hbase.regionserver.wal.HLog.syncer(HLog.java:1314)
> - waiting to lock <0x000000067d54ace0> (a java.lang.Object)
> - locked <0x000000067bf88d58> (a java.lang.Object)
> at
> org.apache.hadoop.hbase.regionserver.wal.HLog.syncer(HLog.java:1283)
> at org.apache.hadoop.hbase.regionserver.wal.HLog.sync(HLog.java:1456)
> at
> org.apache.hadoop.hbase.regionserver.wal.HLog$LogSyncer.run(HLog.java:1235)
> at java.lang.Thread.run(Thread.java:662)
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