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From "Zhu Han (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (CASSANDRA-2976) Severe bug on commit log replay
Date Sat, 30 Jul 2011 13:25:09 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-2976?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Zhu Han resolved CASSANDRA-2976.
--------------------------------

    Resolution: Won't Fix

It is not necessary to maintain the order during log replay, as conflict resolution assures
the eventual consistency.

> Severe bug on commit log replay
> -------------------------------
>
>                 Key: CASSANDRA-2976
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2976
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 0.6.13
>            Reporter: Zhu Han
>   Original Estimate: 4h
>  Remaining Estimate: 4h
>
> For 0.6, the replay order of commit log is determined by modify time(mtime) of commit
log files. The roll and update of a new log segment can be finished under 1ms if the log device
is backed up by BBU or it is a SSD with super capacitor. So the last log segment and previous
segment can have the same mtime.
> While File#listFiles() does not guarantee the order of return files, after sorting by
mtime, it is possible that the new log segment are replayed before old log segment.  This
can causes data loss!
> Here is the output of log,  you can observe from the timestamp in the commit log file
names that new log segment are replayed before old segment...
>  INFO [main] 2011-07-30 01:21:07,569 CommitLog.java (line 171) Replaying /var/lib/cassandra/commitlog/CommitLog-1311959800795.log,
/var/lib/cassandra/commitlog/CommitLog-1310661748573.log, /var/lib/cassandra/commitlog/CommitLog-1311838097776.log
>  INFO [main] 2011-07-30 01:21:07,571 CommitLog.java (line 286) Finished reading /var/lib/cassandra/commitlog/CommitLog-1311959800795.log
>  INFO [main] 2011-07-30 01:21:15,813 CommitLog.java (line 286) Finished reading /var/lib/cassandra/commitlog/CommitLog-1310661748573.log
>  INFO [main] 2011-07-30 01:21:15,865 CommitLog.java (line 286) Finished reading /var/lib/cassandra/commitlog/CommitLog-1311838097776.log
>  INFO [main] 2011-07-30 01:21:15,926 CommitLog.java (line 174) Log replay complete
> I have not checked 0.7.x and 0.8.x, I suppose they both have the same problem.

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