[HBASE-12770] Don't transfer all the queued hlogs of a dead server to the same alive server

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.4.0, 2.0.0
• Fix Version/s: 1.4.0, 1.3.1, 2.0.0
• Component/s: Replication
• Hadoop Flags: Reviewed
• Assignee: Phil Yang
• Reporter: Jianwei Cui
• Created: 29/Dec/14 14:25
• Updated: 17/Jun/22 18:41
• Resolved: 08/Aug/16 08:37

Description

When a region server is down(or the cluster restart), all the hlog queues will be transferred by the same alive region server. In a shared cluster, we might create several peers replicating data to different peer clusters. There might be lots of hlogs queued for these peers caused by several reasons, such as some peers might be disabled, or errors from peer cluster might prevent the replication, or the replication sources may fail to read some hlog because of hdfs problem. Then, if the server is down or restarted, another alive server will take all the replication jobs of the dead server, this might bring a big pressure to resources(network/disk read) of the alive server and also is not fast enough to replicate the queued hlogs. And if the alive server is down, all the replication jobs including that takes from other dead servers will once again be totally transferred to another alive server, this might cause a server have a large number of queued hlogs(in our shared cluster, we find one server might have thousands of queued hlogs for replication). As an optional way, is it reasonable that the alive server only transfer one peer's hlogs from the dead server one time? Then, other alive region servers might have the opportunity to transfer the hlogs of rest peers. This may also help the queued hlogs be processed more fast. Any discussion is welcome.

Issue Links

• breaks: HBASE-26482 HMaster may clean wals that is replicating in rare cases
• duplicates: HBASE-16581 Optimize Replication queue transfers after server fail over