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From: Ben Somers <somers.ben@gmail.com>
To: raindrops@librelist.org
Subject: Raindrops::Middleware::Proxy claims to respond to #body when it does not?
Date: Thu, 17 May 2012 12:07:42 -0700	[thread overview]
Message-ID: <CAO1NZAo6ug83xKRmFYQxwQ4OAuPVE97j_4g-ydums9K3nrRD6Q@mail.gmail.com> (raw)
In-Reply-To: <CAO1NZAo6ug83xKRmFYQxwQ4OAuPVE97j_4g-ydums9K3nrRD6Q@mail.gmail.com>


Currently working on the auto-scaler for unicorn that I mentioned on
that mailing list back in January; I'm writing it as an external tool
that polls against the raindrops middleware to get a crude metric of
load. (Independently, I'd love your thoughts on whether that's a
viable/problematic approach; I think I can safely use the active
count, but details on exactly what those numbers mean would be cool).

In the process, though, I enabled Raindrops::Middleware on a whole
bunch of servers that weren't running it before, and started getting
some pretty weird errors on a few of them. Those boxes run a separate
middleware that writes xml requests to a log file; in the process,
they call #body on the response object. This works great when they're
receiving ActionController::Response objects from Rails, but blows up
on Raindrops::Middleware::Proxy objects.  What I'm seeing is that the
response passed to my logger middleware is a
Raindrops::Middleware::Proxy, with an ActionDispatch::Response set as
its @body. The ActionDispatch::Response responds to #body; the
Raindrops::Middleware::Proxy does not, since it has its body in a
plain instance variable without an accessor.

This tricked my initial workaround, which was to only log the body if
the response responded to #body, because the Middleware::Proxy winds
up claiming that it can respond when in fact it cannot. It does so
because it delegates :respond_to? to its body in almost all cases.

Clearly the Raindrops::Middleware::Proxy has #respond_to? implemented
the way it is for a reason, but it seems awfully counterintuitive.

Thoughts/answers? Not necessarily looking for any action here, just
trying to understand what's going on and why.


PS And yes, I'm totally aware that this logger middleware is dependent
on an interface not provided for in the Rack specification. I've
already complained to its author about this, though it probably falls
on me to correct that.
PPS Running on unicorn 4.3.1, raindrops 0.8.1, and rails 3.0.10, if
that's of any concern.

       reply	other threads:[~2012-05-17 19:08 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-17 19:07 Ben Somers [this message]
2012-05-17 23:18 ` Raindrops::Middleware::Proxy claims to respond to #body when it does not? Eric Wong
2012-05-17 23:37   ` Ben Somers
2012-05-18  0:07     ` Eric Wong

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