shutdown() does not gracefully drain / clear generic pools

[rossj]

Related to #50. I've noticed that after trying to do a graceful shutdown(), my process hangs around for about ~30 seconds. Using wtfnode it seems that there is still a timer from generic-pool that keeps the process running for a while:

[WTF Node?] open handles:
- File descriptors: (note: stdio always exists)
  - fd 1 (tty) (stdio)
  - fd 2 (tty) (stdio)
- Timers:
  - (1000 ~ 1000 ms) (anonymous) @ /code/node_modules/generic-pool/lib/generic-pool.js:256

I'm guessing this is part of generic-pool's idle handling. idleTimeoutMillis defaults to 30s which is about the time I'm seeing before actual process exit.

Perhaps the rascal vhost should drain and clear the pools during shutdown?

From the generic-pool docs:

/**
 * Step 3 - Drain pool during shutdown (optional)
 */
// Only call this once in your application -- at the point you want
// to shutdown and stop using this pool.
myPool.drain().then(function() {
  myPool.clear();
});

I'm new to rascal but I'd be happy to work on a PR if you'd like this change.

[cressie176]

Hi @rossj. Thanks for diagnosing this and the offer of a PR. The channel pooling code is a little ugly, so I'll sort shortly.

[cressie176]

Should be fixed in rascal@4.6.0

[rossj]

Cool, my process exits immediately now. Thanks!