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https://issues.apache.org/jira/browse/HTTPASYNC-86?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Oleg Kalnichevski resolved HTTPASYNC-86.
----------------------------------------
Resolution: Fixed
Fix Version/s: 4.1-beta2
4.0.3
Hi Jose
I could not find a way to resolve the problem without changing the existing
connection interface, so at the end I had to resort to a hack and abuse
#IsStale method. A better fix will have to wait until 5.0. Could you please
re-test the latest snapshot off the trunk or the 4.0.x branch in your
environment?
Oleg
> Race condition in async client when a keep alive connection is reused in POST
> request method
> --------------------------------------------------------------------------------------------
>
> Key: HTTPASYNC-86
> URL: https://issues.apache.org/jira/browse/HTTPASYNC-86
> Project: HttpComponents HttpAsyncClient
> Issue Type: Bug
> Affects Versions: 4.0.2, 4.1-beta1
> Environment: Ubuntu 12.04 64 bits Kernel 3.2.0-74
> Reporter: Jose Dillet
> Fix For: 4.0.3, 4.1-beta2
>
> Attachments: AsyncClientRaceCondition3RequestSample.java,
> AsyncClientRaceConditionSample.java, httpasyncclient-86-log.txt,
> httpasyncclient-test-3req.log, httpasyncclient-test.log
>
>
> I have found a race condition in the async client when a POST request reuses
> a keep alive connection. We have around 2%-4% of our runs in a Continuous
> Integration environment failing because of this issue.
> I have found a consistent way of forcing the failure by using a debugger, so
> I can force the events to happen in the order which uncovers the problem.
> I have tested it on httpasyncclient 4.0.2 / httpcore 4.3.2 and
> httpasyncclient 4.1-beta1 / httpcore 4.4-beta1 and it happens in both
> versions (the lines provided in the steps to reproduce are from version
> 4.0.2).
> How to reproduce:
> 1) Add these breakpoints:
> a - DefaultClientExchangeHandlerImpl:304
> b - DefaultClientExchangeHandlerImpl:168
> 2) Run AsyncClientRaceConditionSample sample program
> Processing first request:
> - Program hits breakpoint a -> Resume
> - Program hits breakpoint b -> Resume
> Processing second request:
> - Program hits breakpoints a and b (in different threads)
> - Resume a)
> - Resume b)
> (Probably adding a small sleep after DefaultClientExchangeHandlerImpl:303
> only for the testing would also uncover the issue).
> ConnectionClosedException is thrown with this stack trace:
> Exception in thread "main" java.util.concurrent.ExecutionException:
> org.apache.http.ConnectionClosedException: Connection closed
> at org.apache.http.concurrent.BasicFuture.getResult(BasicFuture.java:68)
> at org.apache.http.concurrent.BasicFuture.get(BasicFuture.java:77)
> at
> AsyncClientRaceConditionSample.process(AsyncClientRaceConditionSample.java:81)
> at
> AsyncClientRaceConditionSample.main(AsyncClientRaceConditionSample.java:45)
> Caused by: org.apache.http.ConnectionClosedException: Connection closed
> at
> org.apache.http.impl.nio.client.DefaultClientExchangeHandlerImpl.connectionAllocated(DefaultClientExchangeHandlerImpl.java:305)
> at
> org.apache.http.impl.nio.client.DefaultClientExchangeHandlerImpl.access$000(DefaultClientExchangeHandlerImpl.java:63)
> at
> org.apache.http.impl.nio.client.DefaultClientExchangeHandlerImpl$1.completed(DefaultClientExchangeHandlerImpl.java:360)
> at
> org.apache.http.impl.nio.client.DefaultClientExchangeHandlerImpl$1.completed(DefaultClientExchangeHandlerImpl.java:357)
> at
> org.apache.http.concurrent.BasicFuture.completed(BasicFuture.java:115)
> at
> org.apache.http.impl.nio.conn.PoolingNHttpClientConnectionManager$InternalPoolEntryCallback.completed(PoolingNHttpClientConnectionManager.java:465)
> at
> org.apache.http.impl.nio.conn.PoolingNHttpClientConnectionManager$InternalPoolEntryCallback.completed(PoolingNHttpClientConnectionManager.java:449)
> at
> org.apache.http.concurrent.BasicFuture.completed(BasicFuture.java:115)
> at
> org.apache.http.nio.pool.AbstractNIOConnPool.fireCallbacks(AbstractNIOConnPool.java:443)
> at
> org.apache.http.nio.pool.AbstractNIOConnPool.lease(AbstractNIOConnPool.java:276)
> at
> org.apache.http.impl.nio.conn.PoolingNHttpClientConnectionManager.requestConnection(PoolingNHttpClientConnectionManager.java:261)
> at
> org.apache.http.impl.nio.client.DefaultClientExchangeHandlerImpl.requestConnection(DefaultClientExchangeHandlerImpl.java:351)
> at
> org.apache.http.impl.nio.client.DefaultClientExchangeHandlerImpl.start(DefaultClientExchangeHandlerImpl.java:126)
> at
> org.apache.http.impl.nio.client.InternalHttpAsyncClient.execute(InternalHttpAsyncClient.java:129)
> at
> org.apache.http.impl.nio.client.CloseableHttpAsyncClient.execute(CloseableHttpAsyncClient.java:72)
> at
> org.apache.http.impl.nio.client.CloseableHttpAsyncClient.execute(CloseableHttpAsyncClient.java:102)
> at
> org.apache.http.impl.nio.client.CloseableHttpAsyncClient.execute(CloseableHttpAsyncClient.java:87)
> at
> AsyncClientRaceConditionSample.process(AsyncClientRaceConditionSample.java:80)
> ... 1 more
> Some analysis from my side:
> 1 - When the first request is processed, this is the execution order of
> relevant lines (and the thread where it is processed):
> a - (I/O dispatcher 1)
> DefaultClientExchangeHandlerImpl<T>.connectionAllocated(NHttpClientConnection)
> line: 303
> b - (I/O dispatcher 1)
> DefaultClientExchangeHandlerImpl<T>.connectionAllocated(NHttpClientConnection)
> line: 304
> c - (I/O dispatcher 1) CPoolProxy.detach() line: 60
> d - (I/O dispatcher 1)
> DefaultClientExchangeHandlerImpl<T>.responseCompleted() line: 168
> 2 - When the second request is processed c) might happen before b) which
> leads to the problem:
> a - (main)
> DefaultClientExchangeHandlerImpl<T>.connectionAllocated(NHttpClientConnection)
> line: 303
> c - (I/O dispatcher 1) CPoolProxy.detach() line: 60
> b - (main)
> DefaultClientExchangeHandlerImpl<T>.connectionAllocated(NHttpClientConnection)
> line: 304
> e - (main) BasicFuture<T>.failed(Exception) line: 122
> d - (I/O dispatcher 1)
> DefaultClientExchangeHandlerImpl<T>.responseCompleted() line: 168
> The problem is that in case 2 the connection can be closed before request is
> completed because a) is processed in main thread and c) is processed in I/O
> dispatcher thread, so the ordering b < c is not guaranteed.
> However in case 1 because all the events are processed in I/O dispatcher
> thread, the ordering b < c is guaranteed (this seems to be true even if there
> are several dispatcher threads).
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