Liu Shaohui created HBASE-12865:
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Summary: Wals may be deleted before they are replicated to peers
Key: HBASE-12865
URL: https://issues.apache.org/jira/browse/HBASE-12865
Project: HBase
Issue Type: Bug
Reporter: Liu Shaohui
By design, ReplicationLogCleaner guarantee that the WALs being in replication
queue can't been deleted by the HMaster. The ReplicationLogCleaner gets the WAL
set from zookeeper by scanning the replication zk node. But it may get
uncompleted WAL set during replication failover for the scan operation is not
atomic.
For example: There are three region servers: rs1, rs2, rs3, and peer id 10.
The layout of replication zookeeper nodes is:
{code}
/hbase/replication/rs/rs1/10/wals
/rs2/10/wals
/rs3/10/wals
{code}
- t1: the ReplicationLogCleaner finished scanning the replication queue of rs1,
and start to scan the queue of rs2.
- t2: region server rs3 is down, and rs1 take over rs3's replication queue. The
new layout is
{code}
/hbase/replication/rs/rs1/10/wals
/rs1/10-rs3/wals
/rs2/10/wals
/rs3
{code}
- t3, the ReplicationLogCleaner finished scanning the queue of rs2, and start
to scan the node of rs3. But the the queue has been moved to
"replication/rs1/10-rs3/WALS"
So the ReplicationLogCleaner will miss the WALs of rs3 in peer 10 and the
hmaster may delete these WALs before they are replicated to peer clusters.
We encountered this problem in our cluster and I think it's a serious bug for
replication.
Suggestions are welcomed to fix this bug. thx~
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