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From "Darius D." <darius....@gmail.com>
Subject Re: Apache Tomcat unable to send the request. tomcat throwing 502 Gate Way error
Date Tue, 13 Sep 2011 12:19:58 GMT

Hi,

well the problem is that we have the same problem, real strange NPEs in
servlets.

It is more pronounced when using dedicated thread executor, moving to
threads provided by connector itself (with maxThreads="500" option using NIO
) seems to be lowering counts of errors. You could try commenting out the
executor pool and using thread pool provided by connector to see if it helps
your case.


Atm we are seeing 3 modes of failure in our tomcat setup ( nginx reverse
proxy -> tomcat with NIO connector )


1) 
SEVERE: Error finishing response
java.lang.NullPointerException

and/or

SEVERE: Error processing request
java.lang.NullPointerException

in logs. ( could be some app problem, but still shady, as no stack trace is
given, like if exception object is gone itself??? )

2) Sometimes we get 502 like Rakesh in servlets that should be fine ( result
of NPE in real strange places )

3) And most scary ones are the following:

2011 09 13 14:18:20.568 WARN  Servlet  - error response: error=no action
query: [type=groupsChangedAction&v=1315912033175] content type:null
protocol: HTTP/1.0 length:-1 character encoding: null  GET
2011 09 13 14:18:20.937 WARN  Servlet  - error response: error=no action
query: [type=groupsChangedAction&v=1315912699092] content type:null
protocol: HTTP/1.0 length:-1 character encoding: null  GET

In tomcat access log they are shown as:
127.0.0.1 - - [13/Sep/2011:14:18:20 +0300] "GET
/ourapp/servlet/Servlet?type=groupsChangedAction&v=1315912033175 HTTP/1.0"
200 15
127.0.0.1 - - [13/Sep/2011:14:18:20 +0300] "GET
/ourapp/servlet/Servlet?type=groupsChangedAction&v=1315912699092 HTTP/1.0"
200 15

So as you can see, tomcat got that GET reqest with type and v params like it
gets and processes thousands others.

Servlet code looks like:
private void doProcess(HttpServletRequest request, HttpServletResponse
response) throws IOException {
		HttpSession session = request.getSession();
		if (session != null) {

			String action = request.getParameter("type");
			logger.debug("action: " + action);
			
			if (action == null) { 

				printError(request, response,"error=no action");
....

	private void printError(HttpServletRequest request, HttpServletResponse
response, String error) throws IOException {
		logger.warn("error response: " + error + " ip: "  +
request.getRemoteAddr() + " query: [" + request.getQueryString() + "]" + "
content type:" + request.getContentType() + " protocol: " +
request.getProtocol() +  " length:" + request.getContentLength() + "
character encoding: " + request.getCharacterEncoding() + "  " +
request.getMethod());
	    
		response.setContentType("text/plain");
		PrintWriter out = response.getWriter();
		out.print(error);
		out.flush();
		out.close();
	}

It happens several times in a day in bursts ( GC collecting something?).


So really puzzling and random error, tomcat got proper request as shown in
access logs (and even request.getQueryString() is valid :) ) , processed
request from same user 5s ago, will process one more 5s later, but somehow
request is NULL??? Now we handle it by retrying, but such random NULL is
fatal for other servlets and services that throw NPEs and it seems that some
tomcat code is affected too with (1).


I'd grateful if some smart guys could look into this problem and willing to
provide any other info.

BR,

Darius.


P.S. this is kinda thread hijack, but i feel the root cause of these Y
errors in XXXX requests are the same.










rakesh k-3 wrote:
> 
> Hi Darius
> 
> Thanks for reviewing the configurations.
> 
> in our catalina.out we had the stack trace which you had menitoned.
> 
> please find the stack trace information which has been requested.
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:597)
> at
> org.apache.axis2.rpc.receivers.RPCUtil.invokeServiceClass(RPCUtil.java:194)
> at
> org.apache.axis2.rpc.receivers.RPCMessageReceiver.invokeBusinessLogic(RPCMessageReceiver.java:102)
> at
> org.apache.axis2.receivers.AbstractInOutMessageReceiver.invokeBusinessLogic(AbstractInOutMessageReceiver.java:40)
> at
> org.apache.axis2.receivers.AbstractMessageReceiver.receive(AbstractMessageReceiver.java:114)
> at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:173)
> at
> org.apache.axis2.transport.http.HTTPTransportUtils.processHTTPPostRequest(HTTPTransportUtils.java:167)
> at
> org.apache.axis2.transport.http.AxisServlet.doPost(AxisServlet.java:142)
> 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.core.StandardHostValve.invoke(StandardHostValve.java:128)
> 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:286)
> at
> org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
> at
> org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
> at
> org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:354)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> at java.lang.Thread.run(Thread.java:619)
> 
> 
> Darius, if you require more information, i ca provide you the details.
> 
> Regards
> Rakesh
> 
> 
> On Mon, Sep 12, 2011 at 5:49 PM, Darius D. <darius.ski@gmail.com> wrote:
> 
>>
>>
>> rakesh k-3 wrote:
>> >
>> > Hi Christopher
>> >
>> > thanks for viewing m configuration ..as mentioned we are using http
>> > connectors in my configuration not AJP.
>> >
>> > and here are my  configuration details.
>> >
>> > Apache tomcat configuration (server.xml)
>> >
>> > <Executor name="tomcatThreadPool" namePrefix="catalina-exec-"
>> >         maxThreads="150" minSpareThreads="4"/>
>> >     <Connector executor="tomcatThreadPool"
>> >                port="8080" protocol="HTTP/1.1"
>> >                connectionTimeout="20000"
>> >                redirectPort="8443" />
>> >
>> > Apache httpd configuration Httpd.conf.
>> >
>> > ProxyPass / http://localhost:8080 route=msf1
>> >
>> > Regards
>> > Rakesh
>> >
>> >
>> >
>>
>>
>> Hi,
>>
>> can you check your catalina.out to see if there is something like:
>>
>> org.apache.coyote.http11.AbstractHttp11Processor endRequest
>> SEVERE: Error finishing response
>> java.lang.NullPointerException
>>
>> or
>>
>> SEVERE: Error processing request
>> java.lang.NullPointerException
>>
>> without any further details / stack traces ?
>>
>> Darius.
>>
>>
>> --
>> View this message in context:
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>> Sent from the Tomcat - User mailing list archive at Nabble.com.
>>
>>
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>>
> 
> 

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