[Mongrel] Design flaw? - num_processors, accept/close
paul at paulbutcher.com
Tue Oct 16 07:49:51 EDT 2007
On 16 Oct 2007, at 06:49, Zed A. Shaw wrote:
> On Mon, 15 Oct 2007 16:43:34 -0700
> "Brian Williams" <bwillenator at gmail.com> wrote:
>> We recently ran into exactly this issue. Some rails requests were
>> external requests that were taking 5 minutes (networking issues
>> out of our
> Now that's a design flaw. If you're expecting the UI user to wait
> for a backend request that takes 5 minutes then you need to
> redesign the workflow and interface. Do it like asynchronous email
> where the use "sends a request", "awaits a reply", "reads the
> reply", and doesn't deal with the backend processing chain of events.
Zed, you're being obtuse. Of course that isn't what Brian means. What
he's doing is giving a pathological example to illustrate just how
badly the mod_proxy_balancer/mongrel/rails combination behaves when
things go wrong.
Yes, you can mask the problem to some extent by mucking about with
your application (and in fact that's what we've done here), but
that's missing the point.
It is not unreasonable to expect that some actions performed by an
application are "fast" and some are "slow". It's further not
unreasonable to expect a very large difference between the fastest
and the slowest actions (if one action takes 10ms and another takes
1s, that's not unreasonable - but it is a 2 order of magnitude
With the obvious setup, fast actions will be delayed behind slow
actions. This is a Bad Thing.
Furthermore, people are fallible. If I happen to accidentally
introduce an action into my system which takes 10s, yes I've screwed
up and should fix it. But is it reasonable for the fact that I have a
single (possibly very rare) action which takes 10s to mean that all
the other fast actions are affected? Even when most of my mongrels
Of course, this isn't really a problem with Mongrel. It's a problem
with Ruby (which doesn't know what the word "thread" means) and Rails
(which doesn't even manage to successfully make use of the brain-dead
version of threading which Ruby does support).
Snetterton, Castle Combe, Cadwell Park...
Who says I have a one track mind?
MSN: paul at paulbutcher.com
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