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From "Robert Coli (JIRA)" <j...@apache.org>
Subject [jira] Updated: (CASSANDRA-1967) commit log replay shouldn't end with a flush
Date Tue, 11 Jan 2011 21:30:47 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-1967?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Robert Coli updated CASSANDRA-1967:
-----------------------------------

    Affects Version/s: 0.3

> commit log replay shouldn't end with a flush
> --------------------------------------------
>
>                 Key: CASSANDRA-1967
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1967
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 0.3
>            Reporter: Robert Coli
>
> (Apologies in advance if there is some very compelling reason to flush after replay,
of which I am not currently aware. ;D)
> Currently, when a node restarts, the following sequence occurs :
> a) commitlog is replayed
> b) any memtables resulting from a) are flushed 
> c) a new commitlog is opened, new memtables are switched in
> ... (other stuff happens)
> d) node starts taking traffic
> This has side effects, perhaps most seriously the potential of triggering compaction.
As a node is likely to struggle performance-wise after restarting, triggering compaction at
that time seems like something we might wish to avoid.
> I propose that the sequence be :
> a) commitlog is replayed
> b) a new commitlog is opened, new memtables are switched in 
> ... (other stuff happens)
> c) node starts taking traffic
> Looking through the relevant code, the only code that appears to depend on this flush
is at src/java/org/apache/cassandra/db/commitlog/CommitLog.java:112 :
> "
>         // all old segments are recovered and deleted before CommitLog is instantiated.
>         // All we need to do is create a new one.
>         segments.add(new CommitLogSegment());
> "
> Presumably this code would have to be refactored to be aware of the currently open commitlog.

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