Re: Timeout on Rainbows!

[Eric Wong <normalperson-rMlxZR9MS24@public.gmane.org>]

"Lin Jen-Shin (godfat)" <godfat-hOE/xeEBYYIdnm+yROfE0A@public.gmane.org> wrote:
> I am reworking on thread pool for EventMachine, and just realized that
> Rainbows doesn't try to put a timeout for each request. Previously,
> I thought the timeout setup in Unicorn would be used for each request.

The normal timeout is only a last resort (it works when the VM is hosed
on a worker).  ThreadTimeout isn't nearly as reliable because it works
on the same VM/process, and it's still always preferable to rely on
"local" timeouts exposed by every library.  (see
http://unicorn.bogomips.org/Application_Timeouts)

> Then I found Rainbows::ThreadTimeout is probably what I want.
> I wonder, does that make sense to do something like this, wrap the
> application with Rainbows::ThreadTimeout with the same timeout
> time in Unicorn automatically?

<snip>

> Because I saw this in EventMachine model:
> 
>   def worker_loop(worker) # :nodoc:
>     init_worker_process(worker)
>     server = Rainbows.server
>     server.app.respond_to?(:deferred?) and
>       server.app = TryDefer.new(server.app)
>   [...]

That's only because other servers (Thin) support this non-standard
extension by default.  Otherwise, I've always been strongly against
adding non-standard extensions/features into the Rack middleware stack.

> and I think in most cases we would want this timeout for each
> request. The down side might be that then the users cannot
> use their own Rainbows::ThreadTimeout (maybe?) or setup a custom
> threshold.

Right.  And some users (e.g. myself) don't ever use either timeout
feature.  We audit every single line of code and make sure all
potentially long-running method calls have timeouts set appropriately.
(IMNSHO, this is the _only_ way to write applications for a
multi-threaded/evented platform)

> Probably then we could introduce another timeout/threshold config
> in Configurator? I feel it would be common enough.

Not worth it.  It's not reliable enough nor generally useful enough
compared to the regular timeout (which again, is a last resort).
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