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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4446) nodetool drain sometimes doesn't mark commitlog fully flushed
Date Fri, 18 Jan 2013 00:36:13 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4446?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13556803#comment-13556803
] 

Jonathan Ellis commented on CASSANDRA-4446:
-------------------------------------------

No counter mutations are double-counted, only the unflushed system changes are replayed.
                
> nodetool drain sometimes doesn't mark commitlog fully flushed
> -------------------------------------------------------------
>
>                 Key: CASSANDRA-4446
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4446
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core, Tools
>         Environment: ubuntu 10.04 64bit
> Linux HOSTNAME 2.6.32-345-ec2 #48-Ubuntu SMP Wed May 2 19:29:55 UTC 2012 x86_64 GNU/Linux
> sun JVM
> cassandra 1.0.10 installed from apache deb
>            Reporter: Robert Coli
>            Assignee: Jonathan Ellis
>            Priority: Minor
>             Fix For: 1.2.1
>
>         Attachments: 4446.txt, cassandra.1.0.10.replaying.log.after.exception.during.drain.txt
>
>
> I recently wiped a customer's QA cluster. I drained each node and verified that they
were drained. When I restarted the nodes, I saw the commitlog replay create a memtable and
then flush it. I have attached a sanitized log snippet from a representative node at the time.

> It appears to show the following :
> 1) Drain begins
> 2) Drain triggers flush
> 3) Flush triggers compaction
> 4) StorageService logs DRAINED message
> 5) compaction thread excepts
> 6) on restart, same CF creates a memtable
> 7) and then flushes it [1]
> The columnfamily involved in the replay in 7) is the CF for which the compaction thread
excepted in 5). This seems to suggest a timing issue whereby the exception in 5) prevents
the flush in 3) from marking all the segments flushed, causing them to replay after restart.
> In case it might be relevant, I did an online change of compaction strategy from Leveled
to SizeTiered during the uptime period preceding this drain.
> [1] Isn't commitlog replay not supposed to automatically trigger a flush in modern cassandra?

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