Wednesday, April 8, 2015

Debugging MQ Java Client Applications

I find it very difficult to debug the Java client application written for MQ. Most of the error messages are self explanatory but some of the error messages are difficult to diagnose and find the cause. Enable tracing would really help to identify the root of the problem. In this post, we will see how to enable tracing on Java applications.

MQ Trace

Simple MQ Trace enabling can be done by adding a JVM parameter like this
java -Dcom.ibm.mq.commonservices=trace.properties ...
Create trace.properties with the following attributes
Diagnostics.MQ=enabled
Diagnostics.Java=explorer,wmqjavaclasses,all
Diagnostics.Java.Trace.Detail=high
Diagnostics.Java.Trace.Destination.File=enabled
Diagnostics.Java.Trace.Destination.Console=disabled
Diagnostics.Java.Trace.Destination.Pathname=/tmp/trace
Diagnostics.Java.FFDC.Destination.Pathname=/tmp/FFDC
Diagnostics.Java.Errors.Destination.Filename=/tmp/errors/AMQJERR.LOG

Points to be noted

  • Add libraries of IBM JRE (From the directory $JRE_HOME/lib) to CLASSPATH
  • Create the directories /tmp/FFDC, /tmp/trace and /tmp/errors
  • Add read permission to trace.properties
  • Keep an eye on the log file size and make sure to disable logging when not required. Otherwise, it will keep filling the disk space. (Logs size will become some gigs in few hours easily)
One you start the Java Client, it will start printing the trace into the mentioned files. If you want to disable the tracing, make the Diagnostics.MQ property value to disabled so that trace will be stopped. 

JSSE Debug

In case of secure connection with MQ, if you want to enable debug for JSSE, then you can use the JVM parameter java.net.debug with different values
-Djavax.net.debug=true
This prints full trace of JSSE, this can be limited to only handshake by changing the value of the parameter to ssl:handshake
-Djavax.net.debug=ssl:handshake
This prints only the trace related to handshake, all other trace will be simply ignored.

Happy Learning!!!!