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https://issues.apache.org/jira/browse/HBASE-27498?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tak-Lon (Stephen) Wu resolved HBASE-27498.
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Fix Version/s: 2.4.16
2.5.3
Resolution: Fixed
> Observed lot of threads blocked in
> ConnectionImplementation.getKeepAliveMasterService
> -------------------------------------------------------------------------------------
>
> Key: HBASE-27498
> URL: https://issues.apache.org/jira/browse/HBASE-27498
> Project: HBase
> Issue Type: Bug
> Components: Client
> Affects Versions: 2.5.0
> Reporter: Vaibhav Joshi
> Priority: Major
> Fix For: 2.4.16, 2.5.3
>
> Attachments: Screenshot 2022-11-16 at 10.06.59 AM.png
>
>
> Recently We observed that lot of threads are blocked in method
> "ConnectionImplementation.getKeepAliveMasterService" during some
> initialization stages of rolling restart workflow.
> During rolling restart, we make RPC calls to Master using
> RpcRetryingCallerImpl, so as part of initialization we call
> "ConnectionImplementation.getKeepAliveMasterService" for each thread.
> Internally this method do RPC call within a synchronized block to check if
> master is running (mss.isMasterRunning).
> Lots of threads are in blocked state due following synchronized block
> synchronized (masterLock) {
> if (!isKeepAliveMasterConnectedAndRunning(this.masterServiceState))
> { MasterServiceStubMaker stubMaker = new MasterServiceStubMaker();
> this.masterServiceState.stub = stubMaker.makeStub(); }
> resetMasterServiceState(this.masterServiceState);
> }
> In Thread Dump Analyzer (2.4), we get warning that "A lot of threads are
> waiting for this monitor to become available again.
> This might indicate a congestion. You also should analyze other locks
> blocked by threads waiting for this monitor as there might be much more
> threads waiting for it.". Please check attached screenshot !Screenshot
> 2022-11-16 at 10.06.59 AM.png|width=1639,height=971!
> --------------------
> "pool-11-thread-158" #313 prio=5 os_prio=0 tid=0x000055b88bcb8800 nid=0x404e
> waiting for monitor entry [0x00007fa48aa86000]
> java.lang.Thread.State: BLOCKED (on object monitor)
> at
> org.apache.hadoop.hbase.client.ConnectionImplementation.getKeepAliveMasterService(ConnectionImplementation.java:1336)
> - waiting to lock <0x00000005d30ecb68> (a java.lang.Object)
> at
> org.apache.hadoop.hbase.client.ConnectionImplementation.getMaster(ConnectionImplementation.java:1327)
> at
> org.apache.hadoop.hbase.client.MasterCallable.prepare(MasterCallable.java:57)
> at
> org.apache.hadoop.hbase.client.RpcRetryingCallerImpl.callWithRetries(RpcRetryingCallerImpl.java:103)
> at
> org.apache.hadoop.hbase.client.HBaseAdmin.executeCallable(HBaseAdmin.java:3019)
> at
> org.apache.hadoop.hbase.client.HBaseAdmin.executeCallable(HBaseAdmin.java:3011)
> at org.apache.hadoop.hbase.client.HBaseAdmin.move(HBaseAdmin.java:1458)
> at
> org.apache.hadoop.hbase.util.MoveWithoutAck.call(MoveWithoutAck.java:58)
> at
> org.apache.hadoop.hbase.util.MoveWithoutAck.call(MoveWithoutAck.java:33)
> -------------------
>
> *Proposal:*
> We can optimize this flow as follows
> 1. Use double checked lock for
> "isKeepAliveMasterConnectedAndRunning(this.masterServiceState)" so that
> theads don't race for monitor, when master is running.
> 2. "isKeepAliveMasterConnectedAndRunning()" method should reuse the Globally
> cached state of isMasterRunning instead of doing expensive Call in for each
> thread.
> Check PR [https://github.com/apache/hbase/pull/4889] for more details.
> Note: The "master" branch uses "AsyncConnectionImpl" so apparently we don't
> have issues there.
>
>
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