CODEWITHSUNDEEP
javajava-threadsinterrupted-exceptionjava-process-runtime
Bobby
Bobby

Reputation: 11

Can anything external to the JVM interrupt Process.waitFor()?

I've been using roughly the same utility code to handle executing an external Process for at least a decade. Recently a customer hit a case where the following ~code was interrupted:

try {
    int exitCode = myProcess.waitFor();
    // do things with this code
} catch (InterruptedException ie) {
    // log stuff here including thread name, but otherwise swallow the exception
}

We have no code that would interrupt the above, except during shutdown when it doesn't matter that it happened. That wasn't the case here: the user saw the external process interrupted, which meant we didn't have a proper exit code, and something went wrong because of it. Maybe importantly, the thread that was interrupted was "main."

I can only see two possibilities here. Either:

  1. The thread was already interrupted before getting to waitFor().
  2. Something else happened during waitFor() to interrupt it.

We've never seen this happen before (in over ten years with many many users), and I can't find a problem in the code leading up to the above, but it's simple enough for #1 to put in a Thread.interrupted() call to check on it and at least work around the problem.

My question is if anything external could cause #2? I've tried testing by executing an external script that just waits 30 seconds, and I try various ways of killing the processes that were created. But in each of my dumb tests the java Process finishes with a proper exit code. I can't do anything external to cause that waitFor call to be interrupted.

So, anyone know of a way to externally interrupt the process? It'd be good form, of course, to handle it properly throughout the code, but it would be a large change to handle something that might never happen and, worse, is untestable. The simple Thread.interrupted call should not hurt anything and would let us know there's a bug somewhere if we see it; I'm much more comfortable with it.

Note: googling for this has not been helpful since every keyword points to info on handling the interruption, not causing it. Thus my potentially dumb post.

Upvotes: 1

Views: 43

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