Alec Swan wrote:
Hello,
I agree that this is not a bug in Tomcat code, but I would appreciate
any help with troubleshooting this.
Let me tell you about our app. We have a thousands of Metro SOAP
clients which hit our Tomcat server. Some SOAP HTTP requests take over
an hour to process because queries take a very long time to execute in
the database. The clients are configured to never timeout waiting on
the server response.
And could there be something else, between the client and the Tomcat, which could time out
if no activity happens on that connection ?
(I have known of routers/firewalls which did this, to save on connections to
maintain).
So, I can see the following possible causes of the Client Abort
Exception logged by Tomcat:
1. The client drops its connection to the server - I would have
expected the client to get some sort of offline exception and
terminate the request. Instead, the client keeps waiting, so maybe
this is not the problem.
2. Tomcat times out (our connectionTimeout is set to 600000) and
somehow fails to write the response back.
I think that you can rule this one out. The connectionTimeout, if I remember correctly,
only applies to the time between
- when the client establishes the HTTP connection to Tomcat
- and the time when Tomcat receives the actual request on that connection
It is essentially meant to avoid attacks where many clients would create connections to
Tomcat and never send a request (and thus block threads (or at least connected sockets)
for nothing).
But check the documentation to see if maybe this parameter value is taken as a default for
other unspecified timeouts.
3. Tomcat's DBCP connection pool times out
Could anybody help us enable the right kind of logging to verify the
last two possible causes? Can you think of any other ways to
troubleshoot this?
You can set up an AccessLogValve and measure the time taken by each request.
And you can take thread dumps, as mentioned previously, to see what these Tomcat threads
are really doing while the client is waiting.
You can also trace the real packets exchanged via an external protocol analyser such as
Wireshark. That will tell you if it is the client dropping the connection, or if something
in-between is doing that. Tomcat logs can only tell you what happens in Tomcat.
And for Tomcat, if an intermediate agent is dropping the connection, it will also look
like a Client Abort.
Generally speaking, I don't think that there are many explanations for a "Client Abort"
exception. If it was Tomcat doing (or not doing) something and aborting the application,
the error message would be different.
So, considering that this is a clue, and that you have no other clue until now, I would
start by examining that as a possible cause, and not other hypothetical scenarios for
which you have not seen a clue yet.
Thanks,
Alec
On Thu, Aug 4, 2011 at 11:05 AM, André Warnier <a...@ice-sa.com> wrote:
Hi.
It dos not look to me like the problem is in Tomcat per se, but rather in
the application running inside of Tomcat, and/or the client application.
Let me explain what leads me to that supposition :
- according to (1) and (2) below, the SOAP request was sent by the client,
received by Tomcat, and passed by Tomcat to the corresponding application
Then according to the log, an exception occurs *within the application
classes* (not inside Tomcat code). Scrolling down the log, it appears that
:
Caused by: ClientAbortException: java.io.IOException
That would mean that when the webapp within the Tomcat application is trying
to send some output to the client, it finds the client socket closed (by the
client).
This could happen for instance if the client "got tired of waiting" so to
speak, hit some internal timeout waiting for a server response, and decided
to give up and close the socket on which it was waiting for a response.
Then some time later the application tries to send some response, but hits
the closed socket and throws the exception.
That would explain (3) in your list, because from the point of view of
Tomcat then, this application invocation is finished (with an error, but
finished).
Now why the application appears in (4) to still be waiting, I can only then
attribute to some logic error in the application : it gave up waiting and
closed the socket, but still says that it is waiting ?
In any case, in a standard configuration, I do not think that Tomcat would
kill an application by its own decision, even if this application took 30
minutes to return a response.
Maybe a few thread dumps a couple of seconds apart, when Tomcat has received
the SOAP request, may explain what the responding thread is doing that takes
so long before sending a response. There is information in the Tomcat FAQ
about how to do that.
I would also inspect the client code to check if there is a timeout for a
server response, and what it does exactly when that timeout is reached.
A standard browser would have a timeout of approx. 5 minutes, and then it
would display a page saying "the server is taking too long to respond.."
etc..
Biut with other code, it depends on the code.
Alec Swan wrote:
Hello,
We are experiencing a problem on our production servers causing our
HTTP clients to hang. I apologize for cross-posting with Metro forum
but this is a critical problem for us.
It looks like client SOAP HTTP requests get dropped/terminated by
Tomcat or metro without notifying the client that request was
terminated leaving the client waiting indefinitely for response.
Here is what we observed:
1. Client makes a SOAP call to the server
2. Tomcat receives HTTP request and we can see it listed on Tomcat Manager
page
3. After about 5 minutes HTTP request disappears from the list of
active HTTP request
4. The client is still waiting for response
We also noticed the following exception logged in catalina.out. It is
thrown around the same time when the problem above occurs but we are
not sure if there is a direct correlation between them.
Aug 1, 2011 12:07:44 AM
com.sun.xml.ws.transport.http.servlet.WSServletDelegate doGet
SEVERE: caught throwable
javax.xml.ws.WebServiceException: com.ctc.wstx.exc.WstxIOException: null
at
com.sun.xml.ws.encoding.StreamSOAPCodec.encode(StreamSOAPCodec.java:112)
at
com.sun.xml.ws.encoding.SOAPBindingCodec.encode(SOAPBindingCodec.java:278)
at
com.sun.xml.ws.transport.http.HttpAdapter.encodePacket(HttpAdapter.java:383)
at
com.sun.xml.ws.transport.http.HttpAdapter.access$100(HttpAdapter.java:93)
at
com.sun.xml.ws.transport.http.HttpAdapter$HttpToolkit.handle(HttpAdapter.java:529)
at
com.sun.xml.ws.transport.http.HttpAdapter.handle(HttpAdapter.java:288)
at
com.sun.xml.ws.transport.http.servlet.ServletAdapter.handle(ServletAdapter.java:143)
at
com.sun.xml.ws.transport.http.servlet.WSServletDelegate.doGet(WSServletDelegate.java:155)
at
com.sun.xml.ws.transport.http.servlet.WSServletDelegate.doPost(WSServletDelegate.java:189)
at
com.sun.xml.ws.transport.http.servlet.WSServlet.doPost(WSServlet.java:76)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:470)
at
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at
org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:864)
at
org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:579)
at
org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1665)
at java.lang.Thread.run(Unknown Source)
Caused by: com.ctc.wstx.exc.WstxIOException: null
at
com.ctc.wstx.sw.BaseStreamWriter.finishDocument(BaseStreamWriter.java:1687)
at
com.ctc.wstx.sw.BaseStreamWriter.writeEndDocument(BaseStreamWriter.java:585)
at
com.sun.xml.ws.message.saaj.SAAJMessage.writeTo(SAAJMessage.java:368)
at
com.sun.xml.ws.encoding.StreamSOAPCodec.encode(StreamSOAPCodec.java:109)
... 24 more
Caused by: ClientAbortException: java.io.IOException
at
org.apache.catalina.connector.OutputBuffer.doFlush(OutputBuffer.java:319)
at
org.apache.catalina.connector.OutputBuffer.flush(OutputBuffer.java:288)
at
org.apache.catalina.connector.CoyoteOutputStream.flush(CoyoteOutputStream.java:98)
at com.ctc.wstx.io.UTF8Writer.flush(UTF8Writer.java:99)
at
com.ctc.wstx.sw.BufferingXmlWriter.flush(BufferingXmlWriter.java:214)
at
com.ctc.wstx.sw.BufferingXmlWriter.close(BufferingXmlWriter.java:194)
at
com.ctc.wstx.sw.BaseStreamWriter.finishDocument(BaseStreamWriter.java:1685)
... 27 more
Caused by: java.io.IOException
at
org.apache.coyote.http11.InternalAprOutputBuffer.flushBuffer(InternalAprOutputBuffer.java:716)
at
org.apache.coyote.http11.InternalAprOutputBuffer.flush(InternalAprOutputBuffer.java:304)
at
org.apache.coyote.http11.Http11AprProcessor.action(Http11AprProcessor.java:1021)
at org.apache.coyote.Response.action(Response.java:183)
at
org.apache.catalina.connector.OutputBuffer.doFlush(OutputBuffer.java:314)
... 33 more
Any help will be greatly appreciated.
Thanks!
Alec
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