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Re: [aspectj-users] How to weave the method calls inside an war file?

Thanks now it makes sense. Thanks for your valuable input. Let me try it.

Anto.

On 5 Nov 2015 17:35, "Eric B" <ebenzacar@xxxxxxxxx> wrote:
Each concurrent http request will be served by seperate threads, however, when a request is finished, the same thread may be reused to serve additional requests.  This is normal in a webserver.

If you set up a request listener or filter, it will be called at the start of every request.  In this listener, you can set an id.  Depending on the technology stack you are using there are different ways of accomplishing this.
Ex:
public void requestInitialized(ServletRequestEvent sre){
   MDC.put( "userId", new UUID() );
}


or

public void doFilter(...){
   MDC.put( "userId", new UUID() );
   MDC.put( ... ... );
   chain.doFilter(args);
}

This UUID can then be accessed in your logging statement automatically.  In your code, you would use normal logging statements: logger.info("some log info").

Your Appender would be configured with the particular parameter in its string.  Ex:
<param name="ConversionPattern" value="RequestUUID: %X{userId} %d{ISO8601} %-5p %c{1} - %m%n" />

Then your logger would automatically printout your log as something like:
RequestUUID: 12afe1938107 2015-11-04 11:02:03  some.class.Name:159 - some log info


Since the MDC var is overwritten at the start of every request, you can be assured that the thread will contain the appropriate value for that request.  And since all concurrent requests are handled by independent threads, there will be no overlapping.

You should be able to find plenty of resources/tutorials for ways to use MDC online (stackoverflow or other).  Here's a quick primer:

Hope this clarifies things a little.  Let me know if anything is still unclear.

Thanks,

Eric



On Thu, Nov 5, 2015 at 10:59 AM, Anto Aravinth <anto.aravinth.cse@xxxxxxxxx> wrote:

Thanks Eric, thats exactly what I was looking for.

A noob question, so if a user hits the webpage, servlet is going to create a thread for the same. Now if I do logger after setting up MDC id like this:

   logger.info (" Great")

So technically how this can be converted or remembered per thread?

Because imagine I did set the id as 121, and two users are hitting, which is going to be altogether different threads, how does this 121 gets binded to threads in this case?

From my understanding so if a user going to access the webpage, then he or she needs to "somehow" pass on this id to MDC, then I believe it works as required.

Correct me if I'm wrong.

Anto.

On 5 Nov 2015 16:10, "Eric B" <ebenzacar@xxxxxxxxx> wrote:
What logging platform are you using?

If you are using Log4j, you can use the MappedDiagnosticContext (MDC) class https://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/MDC.html.  This is managed on a per-thread basis, so you can assign an ID in the MDC as part of a request listener, and any Log4j call that is made in that thread will have access to the id stored in the MDC.  This allows you to recall the id in a logging statement.

All logs will still be pushed to the same appender, however you would then be able to sort and/or filter based on the ID.  If memory serves, retrieving the variable for the appender is done via the %X{VarName}.

I also believe that Logback has a similar MDC functionality.

Thanks,

Eric



On Thu, Nov 5, 2015 at 9:34 AM, ants <anto.aravinth.cse@xxxxxxxxx> wrote:
I have few questions on this specific task; Now I have written by monitoring
logic in the aspectj. It works so smoothly and tested in tomcat and other
servers as well.

I was wondering, if this can be done as well:

1. The logging gets started when I turn on few params on my aspectj jar,
which starts logging.
2. So if possible, when it logs, can I make it to log according to each
thread level?

What I was thinking over here is this, I will start my logging param in
aspectj, so imagine, when two users access the webpage in the server, now I
want the trace should be completely isolated from each of the request. I
know HTTP doesn't have states, we can do this in sort of attaching some
"sessionID" to each trace, and then do a batch operation for getting the
result of each thread; so that trace "flow" is perfect.

I just want to know if there are any other ways of doing this?

Your thoughts will be really helpful to me.



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