Enis Soztutar created HBASE-6060:
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Summary: Regions's in OPENING state from failed regionservers
takes a long time to recover
Key: HBASE-6060
URL: https://issues.apache.org/jira/browse/HBASE-6060
Project: HBase
Issue Type: Bug
Components: master, regionserver
Reporter: Enis Soztutar
Assignee: Enis Soztutar
we have seen a pattern in tests, that the regions are stuck in OPENING state
for a very long time when the region server who is opening the region fails. My
understanding of the process:
- master calls rs to open the region. If rs is offline, a new plan is
generated (a new rs is chosen). RegionState is set to PENDING_OPEN (only in
master memory, zk still shows OFFLINE). See HRegionServer.openRegion(),
HMaster.assign()
- RegionServer, starts opening a region, changes the state in znode. But that
znode is not ephemeral. (see ZkAssign)
- Rs transitions zk node from OFFLINE to OPENING. See
OpenRegionHandler.process()
- rs then opens the region, and changes znode from OPENING to OPENED
- when rs is killed between OPENING and OPENED states, then zk shows OPENING
state, and the master just waits for rs to change the region state, but since
rs is down, that wont happen.
- There is a AssignmentManager.TimeoutMonitor, which does exactly guard
against these kind of conditions. It periodically checks (every 10 sec by
default) the regions in transition to see whether they timedout
(hbase.master.assignment.timeoutmonitor.timeout). Default timeout is 30 min,
which explains what you and I are seeing.
- ServerShutdownHandler in Master does not reassign regions in OPENING state,
although it handles other states.
Lowering that threshold from the configuration is one option, but still I think
we can do better.
Will investigate more.
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