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From "Pavel Yaskevich (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-7275) Errors in FlushRunnable may leave threads hung
Date Wed, 17 Dec 2014 20:51:14 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7275?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14250519#comment-14250519
] 

Pavel Yaskevich commented on CASSANDRA-7275:
--------------------------------------------

Just to re-iterate, I still don't understand why we would prefer to crash the process if error
happens on the system CF flush e.g. at the end of compaction which is not even essential for
the operation like compactions_in_progress and still there is no clear answer how do we distinguish
between FS{Read, Write}Error which is generated as a response to FS or system failure and
the one which is generated as a response to incorrect call that Cassandra made e.g. "duplicate
hard-link"? 

I would prefer that if the failure was in the system CF we log the message, leave commitlog
and let everything carry on instead of just crashing because it could essentially result in
dropping incoming data, the story is different for actual user memtables tho, as I mentioned
couple of times in my previous comments, I'm total fine crashing if normal memtable flush
fails and disk_failure_policy says so.

> Errors in FlushRunnable may leave threads hung
> ----------------------------------------------
>
>                 Key: CASSANDRA-7275
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7275
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Tyler Hobbs
>            Assignee: Pavel Yaskevich
>            Priority: Minor
>             Fix For: 2.0.12
>
>         Attachments: 0001-Move-latch.countDown-into-finally-block.patch, 7252-2.0-v2.txt,
CASSANDRA-7275-flush-info.patch
>
>
> In Memtable.FlushRunnable, the CountDownLatch will never be counted down if there are
errors, which results in hanging any threads that are waiting for the flush to complete. 
For example, an error like this causes the problem:
> {noformat}
> ERROR [FlushWriter:474] 2014-05-20 12:10:31,137 CassandraDaemon.java (line 198) Exception
in thread Thread[FlushWriter:474,5,main]
> java.lang.IllegalArgumentException
>     at java.nio.Buffer.position(Unknown Source)
>     at org.apache.cassandra.db.marshal.AbstractCompositeType.getBytes(AbstractCompositeType.java:64)
>     at org.apache.cassandra.db.marshal.AbstractCompositeType.getWithShortLength(AbstractCompositeType.java:72)
>     at org.apache.cassandra.db.marshal.AbstractCompositeType.split(AbstractCompositeType.java:138)
>     at org.apache.cassandra.io.sstable.ColumnNameHelper.minComponents(ColumnNameHelper.java:103)
>     at org.apache.cassandra.db.ColumnFamily.getColumnStats(ColumnFamily.java:439)
>     at org.apache.cassandra.io.sstable.SSTableWriter.append(SSTableWriter.java:194)
>     at org.apache.cassandra.db.Memtable$FlushRunnable.writeSortedContents(Memtable.java:397)
>     at org.apache.cassandra.db.Memtable$FlushRunnable.runWith(Memtable.java:350)
>     at org.apache.cassandra.io.util.DiskAwareRunnable.runMayThrow(DiskAwareRunnable.java:48)
>     at org.apache.cassandra.utils.WrappedRunnable.run(WrappedRunnable.java:28)
>     at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
>     at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
>     at java.lang.Thread.run(Unknown Source)
> {noformat}



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