[jira] Commented: (CASSANDRA-134) Support flush based on timer interval, in addtion to size

["Jonathan Ellis (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-134?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12706127#action_12706127 ] 

Jonathan Ellis commented on CASSANDRA-134:
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patch looks ok, but a setting that is low enough to be useful on almost-unused CFs will cause unnecessary flushes on high-traffic ones.

If I were writing it I would take the approach of recording flush time in CFS and then every so often (more frequently than FlushPeriod) scan all CFS and schedule a flush only for those who have not had one already during the last FlushPeriod minutes.

I could also go for the PeriodicFlushManager approach (always flush every FlushPeriod even if it was recently flushed) if FlushPeriod were per-CF.

Either way this is a good thing to have turned on by default so let's include it in the sample config.

> Support flush based on timer interval, in addtion to size
> ---------------------------------------------------------
>
>                 Key: CASSANDRA-134
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-134
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Jun Rao
>            Assignee: Jun Rao
>         Attachments: issue134.patchv1
>
>
> Today, the CFs are flushed purely based on the size of the data accumulated in Memtable. If a table has multiple CFs and some CFs are updated at a much slower pace than others, this can prevent a larger number of log files from being deleted. This is because the CF bit in the log header is only turned off when a CF is flushed. A log can't be deleted until all CF bits in the header are cleared. One solution is to add a background flusher that periodically force-flushes every CF.

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