Implement ThreadPoolExecutor.CallerRunsPolicy?

[billdueber]

I would love to see an implementation of java's ThreadPoolExecutor.CallerRunsPolicy -- it allows automatic throttling, so I need not worry about creating too big a queue or too many threads when using a thread pool.

[jdantonio]

Thank you for the suggestion. That sounds like a reasonable feature. I'm not as familiar with Java as some of my teammates but I'll look into it.

[jdantonio]

@billdueber I've done a little more research into Java thread pools--specifically ThreadPoolExecutor--and I've tried to think of a good Ruby-ish API for this. How does this sound?

• Update CachedThreadPool with a :min_threads constructor option (we already have a :max_threads option
• Update both CachedThreadPool and FixedThreadPool with a :max_queue_size constructor option (the queue size will be unbound if not given)
• Update both CachedThreadPool and FixedThreadPool with an :overload_policy constructor option that has three possible values: :abort, :caller_runs, and :discard (default)
• The overload_policy option is ignored if no max_queue_size option is given
• The :discard policy causes the #post method to return nil and never run the block when the queue grows too big (this will be the default when not explicitly set)
• The :abort policy causes the #post method to raise a ThreadPoolOverloadError exception and never run the block when the queue grows too big
• The :caller_runs policy will (as you suggest) call the block synchronously on the calling thread when the queue grows too big

[jdantonio]

@billdueber This was implemented in pull request #41 and will be in the next release.

[billdueber]

Excellent, and thank you!

[jdantonio]

@billdueber Thank you for the suggestion. The gem is definitely better for it. If you have a chance I'd love to get your input on PR #42. We're deciding what the default configuration for the global thread pool should be.