hc-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Jose Dillet (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HTTPASYNC-86) Race condition in async client when a keep alive connection is reused in POST request method
Date Wed, 17 Dec 2014 13:15:13 GMT

    [ https://issues.apache.org/jira/browse/HTTPASYNC-86?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14249828#comment-14249828
] 

Jose Dillet commented on HTTPASYNC-86:
--------------------------------------

Oleg,

I don't think the connection has been closed by any party. The problem is that one thread
in the client (in the I/O dispatcher) returns the connection to the pool while other thread
in the client (main thread) is still using the same connection. So the main thread gets connection
closed, but the connection is still open AFAICT.

This is the relevant code:

DefaultClientExchangeHandlerImpl: 304 isOpen returns false in this case
if (!managedConn.isOpen()) {
	failed(new ConnectionClosedException("Connection closed"));
}

org.apache.http.impl.nio.conn.CPoolProxy:144

public boolean isOpen() {
	final CPoolEntry local = this.poolEntry;
	if (local != null) {
		return !local.isClosed();
	} else {
		return false;    <--- false is returned here because poolEntry was null (connection was
returned to the pool)
	}
}

I'll try to provide more evidence that the connection has not been closed by inspecting the
network traffic.

Jose


> 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
>         Attachments: AsyncClientRaceConditionSample.java
>
>
> 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).



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@hc.apache.org
For additional commands, e-mail: dev-help@hc.apache.org


Mime
View raw message