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From "zhangduo (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-12951) TestHCM.testConnectionClose is flakey when using AsyncRpcClient as client implementation
Date Mon, 02 Feb 2015 03:50:34 GMT

    [ https://issues.apache.org/jira/browse/HBASE-12951?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14300855#comment-14300855
] 

zhangduo commented on HBASE-12951:
----------------------------------

I think there is a race condition in AsyncRpcChannel. We check shouldCloseConnection several
times in callMethod, but not enough(and even shouldCloseConnection is not volatile...).

In AsyncRpcClient.cancelConnections, we find a AsyncRpcChannel and close it. This is under
a lock protection, but the actual close operation is in another thread. It closes the channel
is the follow order
1. set shouldCloseConnection to true.
2. clean up pending calls.
3. close the netty channel.

And in AsyncRpcChannel.callMethod, we does as follow
1. check shouldCloseConnection 
2. create call and put it into pending calls
3. check is channel is alive and check shouldCloseConnection again(but does nothing if check
failed!)
4. write out request

The problem is at callMethod step 3. Things can happen like this
1. 'callMethod' check shouldCloseConnection, pass
2. 'close' set shouldCloseConnection, and cleanup all pending calls, and close netty channel.
3. 'callMethod' create a pending call and put it into pending calls, then check channel or
shouldCloseConnection, failed, but just return the call.
4. client will wait forever because no one will wake him up.

There is a cleanupTimer but we also shutdown it when close...

> TestHCM.testConnectionClose is flakey when using AsyncRpcClient as client implementation
> ----------------------------------------------------------------------------------------
>
>                 Key: HBASE-12951
>                 URL: https://issues.apache.org/jira/browse/HBASE-12951
>             Project: HBase
>          Issue Type: Bug
>          Components: IPC/RPC
>            Reporter: zhangduo
>
> Sometimes the background thread is stuck in table.get, here is the jstack result.
> "testConnectionCloseThread" prio=10 tid=0x00007fdb296f9800 nid=0x6b5c in Object.wait()
[0x00007fdad1bf9000]
>    java.lang.Thread.State: WAITING (on object monitor)
>         at java.lang.Object.wait(Native Method)
>         - waiting on <0x00000000f192d6e0> (a org.apache.hadoop.hbase.ipc.AsyncCall)
>         at java.lang.Object.wait(Object.java:503)
>         at io.netty.util.concurrent.DefaultPromise.await(DefaultPromise.java:254)
>         - locked <0x00000000f192d6e0> (a org.apache.hadoop.hbase.ipc.AsyncCall)
>         at io.netty.util.concurrent.DefaultPromise.await(DefaultPromise.java:32)
>         at io.netty.util.concurrent.AbstractFuture.get(AbstractFuture.java:31)
>         at org.apache.hadoop.hbase.ipc.AsyncRpcClient.call(AsyncRpcClient.java:181)
>         at org.apache.hadoop.hbase.ipc.AbstractRpcClient.callBlockingMethod(AbstractRpcClient.java:213)
>         at org.apache.hadoop.hbase.ipc.AbstractRpcClient$BlockingRpcChannelImplementation.callBlockingMethod(AbstractRpcClient.java:287)
>         at org.apache.hadoop.hbase.protobuf.generated.ClientProtos$ClientService$BlockingStub.get(ClientProtos.java:31727)
>         at org.apache.hadoop.hbase.client.HTable$4.call(HTable.java:848)
>         at org.apache.hadoop.hbase.client.HTable$4.call(HTable.java:1)
>         at org.apache.hadoop.hbase.client.RpcRetryingCallerImpl.callWithRetries(RpcRetryingCallerImpl.java:120)
>         at org.apache.hadoop.hbase.client.HTable.get(HTable.java:856)
>         at org.apache.hadoop.hbase.client.TestHCM$3.run(TestHCM.java:371)



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