[iolib-devel] poll error leaking from write-sequence

[Stelian Ionescu]

On Mon, 2009-11-16 at 00:12 +0100, Attila Lendvai wrote:
> Stelian, i think it's not against the rules to signal other exceptions
> than stream-error from sequence calls, but it's causing me more and
> more headaches.
> 
> the situation: i want to log errors happening while our web server is
> serving requests, but i want to keep the error log noise-free. network
> related errors are considered noise, so i have a function that decides
> whether the error is coming from the network stream connected to the
> client:
> 
> (def function is-error-from-client-stream? (error client-stream)
>   (bind ((client-stream-fd (iolib:fd-of client-stream)))
>     (or (and (typep error 'stream-error)
>              (eq (stream-error-stream error) client-stream))
>         ;; TODO the rest is fragile and easily breaks when iolib
> changes behavior
>         (and client-stream-fd
>              (and (typep error 'iolib:socket-error)
>                   (eql client-stream-fd (isys:handle-of error)))
>              ;; TODO signalling non stream-error conditions might be
> an iolib bug
>              (and (typep error 'iolib.multiplex:poll-error)
>                   (eql client-stream-fd (iolib.multiplex:poll-error-fd
> error)))))))
> 
> this function keeps getting longer, but the bigger issue is that it
> highly depends on iolib's internal implementation.
> 
> is there any chance to add it to iolib's contracts that it only
> signals stream-error from stream calls like write-sequence? it could
> chain the original condition not to lose information...
> 
> or do you have some other suggestions?

I'd rather not do chaining because that would disallow the use of
restarts. I think it would be better to make sure that only two error
types can come out of a stream operation: CL:STREAM-ERRORs signaled by
the Gray stream layer, and ISYS:SYSCALL-ERRORs signaled by low-level
code.

I've logged it as https://bugs.launchpad.net/iolib/+bug/485392

-- 
Stelian Ionescu a.k.a. fe[nl]ix
Quidquid latine dictum sit, altum videtur.
http://common-lisp.net/project/iolib
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