[jira] [Commented] (HBASE-27498) Observed lot of threads blocked in ConnectionImplementation.getKeepAliveMasterService

["Hudson (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-27498?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17655181#comment-17655181 ] 

Hudson commented on HBASE-27498:
--------------------------------

Results for branch branch-2.4
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> 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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