[HBASE-23035] Retain region to the last RegionServer make the failover slower - ASF JIRA

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Details

Type: Improvement
Status: Resolved
Priority: Major
Resolution: Fixed
Affects Version/s: 3.0.0-alpha-1, 2.3.0, 2.2.1, 2.1.6
Fix Version/s: 3.0.0-alpha-1, 2.3.0, 2.1.7, 2.2.2
Component/s: amv2
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Release Note:

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Since 2.0.0，when one regionserver crashed and back online again, AssignmentManager will retain the region locations and try assign the regions to this regionserver(same host:port with the crashed one) again. But for 1.x.x, the behavior is round-robin assignment for the regions belong to the crashed regionserver. This jira change the "retain" assignment to round-robin assignment, which is same with 1.x.x version. This change will make the failover faster and improve availability.

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Since 2.0.0，when one regionserver crashed and back online again, AssignmentManager will retain the region locations and try assign the regions to this regionserver(same host:port with the crashed one) again. But for 1.x.x, the behavior is round-robin assignment for the regions belong to the crashed regionserver. This jira change the "retain" assignment to round-robin assignment, which is same with 1.x.x version. This change will make the failover faster and improve availability.

Description

Now if one RS crashed, the regions will try to use the old location for the region deploy. But one RS only have 3 threads to open region by default. If a RS have hundreds of regions, the failover is very slower. Assign to same RS may have good locality if the Datanode is deploied on same host. But slower failover make the availability worse. And the locality is not big deal when deploy HBase on cloud.

This was introduced by ~~HBASE-18946~~.