I'm seeing a problem with AsyncNHttpClientHandler in v4.1 of HttpCore. When I
submit a number of requests simultaneously (anything > 12 seems to trigger it
for me), I get this exception:
Caused by: java.lang.NullPointerException
at
org.apache.http.nio.protocol.AsyncNHttpClientHandler.outputReady(AsyncNHttpClientHandler.java:268)
at
org.apache.http.nio.protocol.BufferingHttpClientHandler.outputReady(BufferingHttpClientHandler.java:118)
at
org.apache.http.impl.nio.DefaultNHttpClientConnection.produceOutput(DefaultNHttpClientConnection.java:207)
at
org.apache.http.impl.nio.ssl.SSLClientIOEventDispatch.outputReady(SSLClientIOEventDispatch.java:245)
at
com.qumu.cxf.rt.transport.ahttp.MultiProtocolIOEventDispatch.outputReady(MultiProtocolIOEventDispatch.java:49)
at
org.apache.http.impl.nio.reactor.BaseIOReactor.writable(BaseIOReactor.java:185)
at
org.apache.http.impl.nio.reactor.AbstractIOReactor.processEvent(AbstractIOReactor.java:338)
at
org.apache.http.impl.nio.reactor.AbstractIOReactor.processEvents(AbstractIOReactor.java:315)
at
org.apache.http.impl.nio.reactor.AbstractIOReactor.execute(AbstractIOReactor.java:275)
at
org.apache.http.impl.nio.reactor.BaseIOReactor.execute(BaseIOReactor.java:104)
at
org.apache.http.impl.nio.reactor.AbstractMultiworkerIOReactor$Worker.run(AbstractMultiworkerIOReactor.java:542)
at java.lang.Thread.run(Thread.java:680)
Some details about my code/environment: Each request is submitted on it's own
connection. The requests are all POSTs. I am using SSL, and I cannot seem to
reproduce this over plain HTTP. The server I am connecting to is IIS/7.5. I
am using NTLM authentication (with JCIFS), so I need to keep the connection
alive through several round trips as the NTLM message exchange occurs.
I dug into the HttpCore code, and here is my analysis of what is occurring:
1.) AsyncNHttpClientHandler.connect calls requestReady to send the initial
request. This sets the request on the connection, and the connection starts
writing the request line in response to write events.
2.) The server receives the request line and responds immediately with a 401
Unauthorized. At this point the POST body has not been fully sent to the
server.
3.) AsyncNHttpClientHandler.inputReady is called with the response from the
server. At this point processResponse is called, and my code executes. I
detect that the request needs authentication and I need to retransmit my
request with an auth header, so my ConnectionReuseStrategy says to keep the
connection alive.
4.) When control returns from my code, the code in processResponse calls
connState.resetOutput, clearing the entity and request in connState. There is
still output from the POST body pending.
5.) processResponse calls conn.requestOutput to reenable write events since
the connection is not to be closed.
6.) A write event happens, and DefaultNHttpClientConnection.produceOutput is
called. Since the output from the initial request never finished,
contentEncoder is not null and so AsyncNHttpClientHandler.outputReady is called
instead of requestReady. Since connState was reset, the entity is null and
this NPE happens.
I copied the code of AsyncNHttpClientHandler and added a conn.suspendInput()
call in requestReady:
if (entityReq != null && entityReq.expectContinue()) {
.....
} else {
conn.suspendInput();
}
and a conn.requestInput call in outputReady:
entity.produceContent(encoder, conn);
if(encoder.isCompleted()) {
conn.requestInput();
}
and this seemed to resolve the issue by not allowing the request and response
to overlap, but I'm not sure this is the best way to fix it.
Is my analysis correct? If so, is there a better way to fix this?
Mike Poindexter
