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Posted to notifications@accumulo.apache.org by "Josh Elser (JIRA)" <ji...@apache.org> on 2015/05/10 02:45:59 UTC
[jira] [Reopened] (ACCUMULO-3423) speed up WAL roll-overs
[ https://issues.apache.org/jira/browse/ACCUMULO-3423?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Josh Elser reopened ACCUMULO-3423:
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After finding another issue with WALs being deleted prematurely, I'm working on reverting these changes for 1.7. I'll leave them in place for 1.8/master.
> speed up WAL roll-overs
> -----------------------
>
> Key: ACCUMULO-3423
> URL: https://issues.apache.org/jira/browse/ACCUMULO-3423
> Project: Accumulo
> Issue Type: Improvement
> Components: master, tserver
> Reporter: Eric Newton
> Assignee: Eric Newton
> Priority: Blocker
> Fix For: 1.8.0
>
> Attachments: WAL-slowdown-graphs.jpg
>
> Time Spent: 40m
> Remaining Estimate: 0h
>
> After reading the proposal on HBASE-10278, I realized there are many ways to make the Accumulo WAL roll-over faster.
> # Open two WALogs, but use only one until it reaches the WALog roll-over size
> # Rollover consists only of swapping the writers
> # WALog roll consists of the final close, which can happen in parallel
> # Don't mark the tablets with log entries: they are already marked with the tserver
> # The tserver can make notes about the logs-in-use in the metadata table(s) as part of opening the log.
> # The master can copy the log entries to tablets while unassigning them, piggybacking on the unassigment mutation.
> # Tablet servers can remove their current log entries from the metadata tables when they have no tablets using them.
> There are two issues:
> # tablets will have an empty file in recovery, nearly all the time, but the recovery code already handles that case.
> # presently, a tablet doesn't have a marker for a log it did not use. Many more tablets will attempt to recover when it is unnecessary.
> This would also address ACCUMULO-2889.
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