Jonathan Ellis created CASSANDRA-4237:
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Summary: Add back 0.8-style memtable_lifetime feature
Key: CASSANDRA-4237
URL: https://issues.apache.org/jira/browse/CASSANDRA-4237
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
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
http://www.fsl.cs.sunysb.edu/~pshetty/socc11-gtssl.pdf: 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 optimization.
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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