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From "Yuki Morishita (JIRA)" <>
Subject [jira] [Updated] (CASSANDRA-4237) Add back 0.8-style memtable_lifetime feature
Date Thu, 06 Sep 2012 15:37:07 GMT


Yuki Morishita updated CASSANDRA-4237:

    Attachment: 4237.txt

OK, this attached version schedules flush at Memtable creation when memtable_flush_period_in_ms
is set, and it tries to keep flushing at the same interval after memtable is expired.
> Add back 0.8-style memtable_lifetime feature
> --------------------------------------------
>                 Key: CASSANDRA-4237
>                 URL:
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>    Affects Versions: 1.0.0
>            Reporter: Jonathan Ellis
>            Assignee: Yuki Morishita
>            Priority: Minor
>             Fix For: 1.2.0
>         Attachments: 4237.txt
> Back in 0.8 we had a memtable_lifetime_in_minutes setting.  We got rid of it in 1.0 when
we added CASSANDRA-2427, which is a better way to  ensure flushing on low-activity memtables.
> However, at the same time we also added the ability to disable durable writes.  So it's
entirely possible to configure a low-activity memtable, that isn't part of the commitlog.
 So, we should add back a memtable lifetime setting.
> An additional motive is pointed out by
if you have a *high* activity columnfamily, and don't require absolute durability, the commitlog
is redundant if you are flushing faster than the commitlog sync period.  So, disabling durable
writes but setting memtable lifetime to the same as the commitlog sync would be a reasonable
> Thus, when we add back memtable lifetime, I think we should measure it in seconds or
possibly even milliseconds (to match commitlog_sync_period) rather than minutes.

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