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https://issues.apache.org/jira/browse/HTTPCLIENT-881?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Oleg Kalnichevski resolved HTTPCLIENT-881.
------------------------------------------

    Resolution: Fixed

Tim

There was a regression in the test suite with your patch. I came up with a 
slight variation on your patch that appears to fix the race condition while 
preserving compatibility with the original behaviour of HttpUriRequest#abort(). 
Please pull the latest code from the SVN repository, review the changes an 
confirm the problem has been adequately fixed.

I did not investigate thoroughly why those test cases started to fail. It can 
well be the test cases are flawed somehow.

Oleg

----
Results :

Tests in error:
  testAbortDuringConnecting(org.apache.http.impl.conn.TestTSCCMWithServer)
  testAbortBeforeSocketCreate(org.apache.http.impl.conn.TestTSCCMWithServer)
  testAbortAfterSocketConnect(org.apache.http.impl.conn.TestTSCCMWithServer)
  testAbortAfterOperatorOpen(org.apache.http.impl.conn.TestTSCCMWithServer)

Tests run: 477, Failures: 0, Errors: 4, Skipped: 0
----

> AbstractClientConnAdapter doesn't ensure that only one of 
> ConnectionReleaseTrigger.abortConnection, .releaseConnection has effect
> ---------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HTTPCLIENT-881
>                 URL: https://issues.apache.org/jira/browse/HTTPCLIENT-881
>             Project: HttpComponents HttpClient
>          Issue Type: Bug
>          Components: HttpConn
>    Affects Versions: 4.0 Final
>            Reporter: Tim Boemker
>             Fix For: 4.1 Alpha1
>
>         Attachments: HTTPCLIENT-881.patch
>
>
> If HttpUriRequest.abort() is called at about the same time that the request 
> completes, it's possible for an aborted connection to be returned to the 
> pool.  The next time the connection is used, HttpClient.execute fails without 
> retrying, throwing this exception:
> java.io.IOException: Connection already shutdown
>       at 
> org.apache.http.impl.conn.DefaultClientConnection.opening(DefaultClientConnection.java:112)
>       at 
> org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:120)
>       at 
> org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:147)
>       at 
> org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:101)
>       at 
> org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:381)
>       at 
> org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:641)
>       at 
> org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:576)
> Steps to reproduce:
> 1) Set a breakpoint in ThreadSafeClientConnManager.releaseConnection just 
> after "reusable" is set (and found to be true).
> 2) Run to the breakpoint in releaseConnection.
> 3) Call HttpUriRequest.abort.
> 4) Let releaseConnection complete.
> When the connection is next used, the exception will be thrown.
> Snippet from ThreadSafeClientConnManager:
>     public void releaseConnection(ManagedClientConnection conn, long 
> validDuration, TimeUnit timeUnit) {
>               ...
>             boolean reusable = hca.isMarkedReusable();
>             if (log.isDebugEnabled()) {                             // 
> breakpoint here
>                 if (reusable) {
>                     log.debug("Released connection is reusable.");
>                 } else {
>                     log.debug("Released connection is not reusable.");
>                 }
>             }
>             hca.detach();
>             if (entry != null) {
>                 connectionPool.freeEntry(entry, reusable, validDuration, 
> timeUnit);
>             }
>         }
>     }
> I think that AbstractClientConnAdapter should be modified as follows:
> 1) Add "released" flag:
>     /** True if the connection has been released. */
>     private boolean released;
> 2) Modify abortConnection:
>     public void abortConnection() {
>         synchronized(this) {
>             if (aborted || released) {
>                 return;
>             }
>             aborted = true;
>         }
>         unmarkReusable(); // this line and all that follow unchanged
> 3) Modify releaseConnection:
>     public void releaseConnection() {
>         synchronized(this) {
>             if (aborted || released) {
>                 return;
>             }
>             released = true;
>         }
>         if (connManager != null) {
>             connManager.releaseConnection(this, duration, 
> TimeUnit.MILLISECONDS);
>         }
>     }

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