Hi Eric
Oleg Kalnichevski wrote:
On Sun, 2008-07-20 at 16:39 +0200, Hubert, Eric wrote:
Hi devs,
we are facing an issue in Apache Synapse where HttpClientWorkers are in
the process of writing a response back to the client using
HttpCoreNIOSender.sendAsyncResponse(), but are then waiting at
org.apache.http.nio.util.SharedOutputBuffer.flushContent() to get
notified by someone...
I'd like to take this issue as a start to gather more knowledge about
the internal working of Apache Synapse and http core nio in general.
Could someone please point me to some documentation, which describes,
how the request/response processing is working.
Eric,
I am very sorry but we currently have almost nothing in terms of
documentation for HttpCore. I am planning to start working on an
HttpCore tutorial in August.
Asankha knows best about the Synapse NIO transport. I'll happily chip
in information about HttpCore internal stuff
...
I know that ideally I should have made more documentation available on
the NIO transport implementation, but due to other work I am involved
with, this has gone down in my TODO list.. I will try to come back to
this in the near future.. However, HttpCore/NIO is where the really cool
code exists, and Synapse/Axis2 is merely using it..
The response is processed by the ClientWorker who delegates the response
processing to Axis2 (again the blackbox of AxisEngine.receive,
AxisEngine.send) and then the response shall be send back to the client
over the MessageFormatter which again uses some NIO buffer. Here we have
the trouble that the code in
org.apache.http.nio.util.SharedOutputBuffer.flushContent() is waiting
for some notification. Who is responsible for that notification?
It expects a notification from the I/O reactor it is ready to accept
more output.
This is because we recently enhanced the way we converted from NIO
channels to Java streams, using the shared buffers available in
HttpCore/NIO. In addition, we now throttle the connection, and suspend
IO on the socket when the corresponding buffer is filled up - and
prevents out of memory errors, and allows the transport to operate with
constant memory.
The
HttpCoreNIOSender.reactor? I couldn't find any useful API-doc on this.
I'm also looking for some httpcore-nio-4.0-beta1-sources.jar from any
Maven Repo to attach to my synapse-IDE project.
Does anybody know something about possible causes for not getting such a
notification?
I was able to reproduce a 'simulated' case of what you experienced, and
this was caused by a connection close while the worker thread was
writing data and waiting on the flushContent() for a large response.
Once you confirm the temporary fix I provided you, I will check it into
the trunk with a JIRA so that it goes into the next release
asankha
--
Asankha C. Perera
WSO2 - http://wso2.org
http://esbmagic.blogspot.com
