java Process' inputStream stuck

Question

Here\'s my scenario:

1. process A spawns child process B and spins threads to drain B\'s outputs.
2. process B spawns daemon process C and drains its outputs, t

Answer 1

I just encountered the same problem. I think I have a workaround to the problem. In process A, I have the following code fragment after Process.waitFor(), where outT and errT are the threads to read process B's stdout and stderr, respectively:

try {
  outT.join(1000);
  if (outT.isAlive()) {
    errmsg("stdout reader still alive, interrupting", null);
    outT.interrupt();
  }
} catch (Exception e) {
  errmsg("Exception caught from out stream reader: "+e, e);
}
try {
  errT.join(1000);
  if (errT.isAlive()) {
    errmsg("stderr reader still alive, interrupting", null);
    errT.interrupt();
  }
} catch (Exception e) {
  errmsg("Exception caught from err stream reader: "+e, e);
}
p.destroy();

Not sure if p.destroy() is needed, but I have been trying all kinds of combinations to deal with the problem.

Anyway, in the run() method of the outT/errT threads, I have the following, where the 'pipe' variable is a Writer instance I am capturing stdout/stderr of the sub-process to. The 'in' variable is the stdout, or stderr, stream obtained from Process:

try {
  r = new BufferedReader(new InputStreamReader(in, enc));
  String line;
  while (true) {
    if (Thread.currentThread().isInterrupted()) {
      errmsg("Text stream reader interrupted", null);
      break;
    }
    if (r.ready()) {
      line = r.readLine();
      if (line == null) {
        break;
      }
      pipe.write(line);
      pipe.write(SystemUtil.EOL);
      if (autoFlush) {
        pipe.flush();
      }
    }
  }
  pipe.flush();

} catch (Throwable t) {
  errmsg("Exception caught: "+t, t);
  try { pipe.flush(); } catch (Exception noop) {}

} finally {
  IOUtil.closeQuietly(in);
  IOUtil.closeQuietly(r);
}

It seems that I never get an EOF indication from any sub-process, even after the sub-process terminates, hence, all the chicanery above to prevent stale threads and blocking.