How to redirect JVM output without tear up output from the application?

Question

Recently I am writing some micro-benchmark code, so I have to print out the JVM behaviors along with my benchmark information. I use

-XX:+PrintCompilation
-XX:+PrintGCDetails

and other options to get the JVM status. For benchmark information, I simply use System.out.print() method. Because I need to know the order of the message I printed and the JVM output.

I can get good result when I just print them out in the console, although the JVM output sometimes tear my messages up, but since they are in different threads, it is understandable and acceptable.

When I need to do some batch benchmarks, I'd like to redirect the output into a file with pipe (> in Linux system), and use python to get the result from the file and analyse it.

Here is the problem:

The JVM output always overlapped with the messages I printed in the Java application. It ruined the completion of the messages.

Any idea how to deal with this situation? I need both the JVM output and application output in the same place in order to preserve the sequence because it is important. And they do not overlap on each other so I don't lose anything.

Answer 1

I would suggest taking a slight detour and looking at using Java Instrumentation APIs - use (write) a simple Java Agent to do this. From your benchmarking perspective, this will give you far more power as well. You could use your Java Agent to log everything (and hence there would be no contention between different logger threads).

You can read more at http://www.javabeat.net/2012/06/introduction-to-java-agents/ or http://today.java.net/pub/a/today/2008/04/24/add-logging-at-class-load-time-with-instrumentation.html