[HBASE-11793] RegionStates shouldn't be locked while writing to META

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Won't Fix
• Component/s: Region Assignment
• Assignee: Unassigned
• Reporter: Virag Kothari
• Created: 20/Aug/14 23:59
• Updated: 17/Jun/22 17:04
• Resolved: 17/Jun/22 17:04

Description

Following scenario with zk-less assignment
Two shutdown handler threads are running where one is METAServerShutdownHandler.
The ServershutdownHandler thread doing recovering of region server other than META acquires lock on RegionStates while doing serverOffline() operation. It keeps the lock while its trying to write to META (not assigned)

Thread 118 (MASTER_SERVER_OPERATIONS-gsbl90723:50510-2):
State: TIMED_WAITING
Blocked count: 430
Waited count: 36755
Stack:
java.lang.Object.wait(Native Method)
org.apache.hadoop.hbase.client.AsyncProcess.waitForNextTaskDone(AsyncProcess.java:853)
org.apache.hadoop.hbase.client.AsyncProcess.waitForMaximumCurrentTasks(AsyncProcess.java:879)
org.apache.hadoop.hbase.client.AsyncProcess.waitUntilDone(AsyncProcess.java:892)
org.apache.hadoop.hbase.client.HTable.backgroundFlushCommits(HTable.java:968)
org.apache.hadoop.hbase.client.HTable.flushCommits(HTable.java:1252)
org.apache.hadoop.hbase.client.HTable.put(HTable.java:910)
org.apache.hadoop.hbase.master.RegionStateStore.updateRegionState(RegionStateStore.java:223)
org.apache.hadoop.hbase.master.RegionStates.updateRegionState(RegionStates.java:804)
org.apache.hadoop.hbase.master.RegionStates.updateRegionState(RegionStates.java:329)
org.apache.hadoop.hbase.master.RegionStates.updateRegionState(RegionStates.java:298)
org.apache.hadoop.hbase.master.RegionStates.regionOffline(RegionStates.java:449)
org.apache.hadoop.hbase.master.RegionStates.regionOffline(RegionStates.java:429)
org.apache.hadoop.hbase.master.RegionStates.serverOffline(RegionStates.java:498)
org.apache.hadoop.hbase.master.AssignmentManager.processServerShutdown(AssignmentManager.java:3404)
org.apache.hadoop.hbase.master.handler.ServerShutdownHandler.process(ServerShutdownHandler.java:214)

In meanwhile, MetaServerShutdownHandler thread cant assign META as it is blocked on RegionStates lock

Thread 126 (MASTER_META_SERVER_OPERATIONS-gsbl90723:50510-0):
State: BLOCKED
Blocked count: 52
Waited count: 100
Blocked on org.apache.hadoop.hbase.master.RegionStates@7398b4c1
Blocked by 118 (MASTER_SERVER_OPERATIONS-gsbl90723:50510-2)
Stack:
org.apache.hadoop.hbase.master.RegionStates.clearLastAssignment(RegionStates.java:422)
org.apache.hadoop.hbase.master.RegionStates.logSplit(RegionStates.java:418)
org.apache.hadoop.hbase.master.handler.MetaServerShutdownHandler.process(MetaServerShutdownHandler.java:79)

As the first thread wont be able to write to META, it keeps on retrying (the retry time is huge: hbase.client.retries.number*10) till it fails.
During that time MetaServerShutdownHandler is blocked.
Also the first thread calls abort on Master as it had failed, but to aggravate the problem, Master wont abort as it also wants to lock the RegionStates

Blocked on org.apache.hadoop.hbase.master.RegionStates@7398b4c1
Blocked by 118 (MASTER_SERVER_OPERATIONS-gsbl90723:50510-2)
Stack:
org.apache.hadoop.hbase.master.RegionStates.getRegionsInTransition(RegionStates.java:152)
org.apache.hadoop.hbase.master.AssignmentManager.updateRegionsInTransitionMetrics(AssignmentManager.java:3081)
org.apache.hadoop.hbase.master.HMaster.doMetrics(HMaster.java:751)
org.apache.hadoop.hbase.master.HMaster.loop(HMaster.java:738)
org.apache.hadoop.hbase.master.HMaster.run(HMaster.java:607)

Seems region states shouldn't be locked when IO is happening.

Issue Links

• is related to: HBASE-11290 Unlock RegionStates
• is related to: HBASE-11059 ZK-less region assignment
• is related to: HBASE-11546 Backport ZK-less region assignment to 0.98