Question

I have a batch process that converts WAV to MP3 sequentially. The problem is that after a few thousand there are too many files left open, and it runs up against the file limit.

The reason it does this is because of the code in SystemCommandTasklet:

FutureTask<Integer> systemCommandTask = new FutureTask<Integer>(new Callable<Integer>() {
    public Integer call() throws Exception {
        Process process = Runtime.getRuntime().exec(command, environmentParams, workingDirectory);
        return process.waitFor();
    }
});

This has the nasty side effect of making me rely on the JVM to clean up the processes, leaving files open and such.

I’ve rewritten it to be so:

FutureTask<Integer> systemCommandTask = new FutureTask<Integer>(new Callable<Integer>() {
    public Integer call() throws Exception {
        Process process = Runtime.getRuntime().exec(command, environmentParams, workingDirectory);
        int status = process.waitFor();

        process.getErrorStream().close();

        process.getInputStream().close();

        process.getOutputStream().flush();
        process.getOutputStream().close();

        process.destroy();

        return status;
    }

});

I’m 95% certain that this works on my mac (thanks to lsof), but how do I make a proper test that will work on any system to PROVE that what I am trying to do is actually working?

Answer 1

A proof will be difficult. But …

Create a (Dummy)command that doesn’t do much but keeps a lock on the files, just as the real thing. This makes sure your test doesn’t depend on the actual command used.

Create a test that starts SystemCommandTask, using the old version, but the DummyCommand. Make it start the task often, until you get the expected exception. Lets call the number of Tasks needed N

Change the test to start 100xN Tasks.

Change the Task to the new version. If the test goes green you should be reasonably sure that your code works.