[CASSANDRA-4237] Add back 0.8-style memtable_lifetime feature

• Type: New Feature
• Status: Resolved
• Priority: Low
• Resolution: Fixed
• Fix Version/s: 2.0 beta 1
• Assignee: Yuki Morishita
• Reporter: Jonathan Ellis

Authors

Yuki Morishita

Reviewers

Jonathan Ellis

• Created: 10/May/12 18:41
• Updated: 16/Apr/19 09:32
• Resolved: 15/Nov/12 16:04

Description

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.