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From Pid <...@pidster.com>
Subject Re: Request params randomly null in servlet(s)
Date Wed, 14 Sep 2011 08:52:20 GMT
On 14/09/2011 08:34, Darius D. wrote:
> 
> Hi,
> 
> we have a problem of request params beeing null in servlets where it
> shouldn't be ( post or get, in get we can even see that
> request.getQueryString() is fine, but params are null).
> 
> 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. 
> 
> 
> 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 (from nginx, that got upstream error) like Rakesh in
> other thread, from 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:

doProcess(req, res) is not a Servlet API method. What other method(s)
call it?

> 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.

Usually this type of thing occurs because the request (or response) is
being held as an instance field somewhere in a thread-unsafe way.


p

> Only connector running is:
>     <Connector port="8080"
> protocol="org.apache.coyote.http11.Http11NioProtocol"
>                connectionTimeout="20000"
>                enableLookups="false"
>                acceptCount="1000"
>                maxThreads="500"
>                maxPostSize="10485760"
>                 />
> 
> Also using 
> <Valve className="org.apache.catalina.valves.RemoteIpValve"
>         protocolHeader="X-Forwarded-Proto" />
> 
> 
> BR,
> 
> Darius. 
> 
> 
> 
> 



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