[HBASE-12577] Disable distributed log replay by default

• Type: Sub-task
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Fix Version/s: 0.99.2
• Hadoop Flags: Reviewed

Release Note

Disabled Distributed Log Replay (DLR) as default WAL/hlog splitting mechanism. 1.0.x releases will default to Distributed Log Splitting (DLS) system which is the default for 0.98, 0.96 and 0.94 releases.

DLR improves MTTR (the more regions a server is carrying, the better the improvement. Also, we can start taking writes during WAL/hlog recovery), but rolling upgrade to HBase-1.0.x from earlier releases of 0.98 branch (0.98.0,..,0.98.3) can result in data loss. If you are not doing rolling upgrade, or you are rolling upgrading from a 0.98 greater than or equal to 0.98.4, you can safely turn on distributed log replay by default. Regular upgrade (as opposed to rolling upgrade) is not affected. See HBASE-11094 for details.

See HBASE-7006 to learn more about DLR. You can enable this feature by setting hbase.master.distributed.log.replay to true in your hbase-site.xml file.

• Assignee: Jeffrey Zhong
• Reporter: Enis Soztutar
• Created: 25/Nov/14 19:02
• Updated: 29/Apr/15 02:18
• Resolved: 01/Dec/14 22:21

Description

Distributed log replay is an awesome feature, but due of HBASE-11094, the rolling upgrade story from 0.98 is hard to explain / enforce.

The fix for HBASE-11094 only went into 0.98.4, meaning rolling upgrades from 0.98.4- might lose data during the upgrade.

I feel no matter how much documentation / warning we do, we cannot prevent users from doing rolling upgrades from 0.98.4- to 1.0. And we do not want to inconvenience the user by requiring a two step rolling upgrade.

Thus I think we should disable dist log replay for 1.0, and re-enable it again for 1.1 (if rolling upgrade from 0.98 is not supported).

ie. undo: HBASE-10888

Issue Links

• is related to: HBASE-13584 Disable distributed log replay by default for 1.1