Hello,
I'm seeing IOExceptions when writing/flushing my Comet servlet
OutputStream. The fist exception is difficult to pinpoint, but it seems
it raises and ERROR event which ultimately enacts a event.close(). This
in turn results in the following stack trace for subsequent operations:
java.lang.NullPointerException
at
org.apache.coyote.http11.InternalNioOutputBuffer.addToBB(InternalNioOutputBuffer.java:620)
at
org.apache.coyote.http11.InternalNioOutputBuffer.commit(InternalNioOutputBuffer.java:611)
at
org.apache.coyote.http11.Http11NioProcessor.action(Http11NioProcessor.java:1033)
at org.apache.coyote.Response.action(Response.java:183)
at org.apache.coyote.Response.sendHeaders(Response.java:379)
at
org.apache.catalina.connector.OutputBuffer.doFlush(OutputBuffer.java:305)
at
org.apache.catalina.connector.OutputBuffer.flush(OutputBuffer.java:288)
at
org.apache.catalina.connector.CoyoteOutputStream.flush(CoyoteOutputStream.java:98)
... <clipped>
This is all well and good, but without understanding why the first IOEx
is happening I'm toast.
My research unearthed this old thread
http://mail-archives.apache.org/mod_mbox/tomcat-users/200712.mbox/%3c47741009.7070...@cedrofinances.com.br%3e
("Comet servlet synchronization and flush problems")
I've verified I'm sync'ing on the OutputStream for all write/flush
operations, and I'm calling response.flushBuffer() in the BEGIN event,
I'm not calling event.close() outside of the ERROR / TIMEOUT / END event
processing and none of them are being called before the original
IOException.
I'm looking for suggestions for other fail-safe practices. Is there
something obvious I'm missing here?
I see from the comet wiki (http://wiki.apache.org/tomcat/WhatIsComet)
that while it's a little out-dated, it indicates "Inaccurate use of non
blocking write API" could be the cause. However, the isWriteable() API
discussed isn't available. For my testing purposes I put in a forced
sleep after both write() and flush() but I'm still encountering the
mysterious ioexceptions (somewhat sporadically).
I'm ready to accept this idea this is a problem in my code, but the
byte[] I'm pushing down looks valid, I'm sync'ing on the response,
outputstream, write, and even globally on my sendResponse method... just
to be safe. So yeah, I'm running out of ideas.
Any thoughts, suggestions, and advice are greatly appreciated!
Thanks in advance,
JW
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