Re: Middleware and post-request processing

[George <george.ogata@gmail.com>]

On Jun 3, 7:23 pm, ghazel <gha...@gmail.com> wrote:
> It seems to me that Rack is in need of a new post-response stage of
> processing. This stage would occur after the response is fully written
> and the client is unblocked, and before the next request is processed.
>
> Similar to what OobGC (http://bogomips.org/unicorn.git/tree/lib/unicorn/oob_gc.rb#n59
> ) accomplishes, it is sometimes useful to perform additional
> operations after the response is written without blocking the client.
> For example, the Oink middleware logs statistics about the request,
> but blocks the response since it has no ability not to: (https://github.com/noahd1/oink/blob/4158d71bc9150f011072b2c6eefe73c72...
> ). This processing takes time, and needlessly delays the response.
>
> This proposal would entail something like a single function which is
> called on each middleware after the response is written to the client
> and the socket is closed (depending on the server implementation). For
> servers which have no ability to not block the client or delay further
> requests the function should still be called, and the impact would be
> similar to the behavior today.
>
> Thoughts?

I'm very much in favor of adding such a hook also.

I wrote a gem which does it for a bunch of common web servers:
http://github.com/oggy/rack_after_reply . It adds a list of callback
functions which just get added to the rack environment. I like this
interface in that keeps the callbacks request-local, rather than just
exposing a global hook. Beyond that, I'm totally open to suggestions.

Of course I'd love it if web server authors would provide such a hook
natively, or even maintain the adapter for their server in this gem.

George