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<H1>[99s-extend] REST handler failure</H1>
<B>Daniel Goertzen</B>
<A HREF="mailto:extend%40lists.ninenines.eu?Subject=Re%3A%20%5B99s-extend%5D%20REST%20handler%20failure&In-Reply-To=%3CCAJCf5Rx_o66FDE-91kX_%3DKBQou9wcx%2BUEenGPFYLE2nR_PRh8g%40mail.gmail.com%3E"
TITLE="[99s-extend] REST handler failure">daniel.goertzen at gmail.com
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<I>Wed Oct 30 16:32:47 CET 2013</I>
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<PRE>Returning 'halt' caused a status code of 204.
Dan.
On Wed, Oct 30, 2013 at 10:27 AM, Ivan uemlianin <<A HREF="https://lists.ninenines.eu/listinfo/extend">ivan at llaisdy.com</A>> wrote:
><i> Instead of <<"this body ignored">> can you return the atom halt?
</I>><i>
</I>><i> #dontevenhaveanyofmycodewithme:(
</I>><i>
</I>><i> Ivan
</I>><i>
</I>><i> --
</I>><i> festina lente
</I>><i>
</I>><i>
</I>><i> On 30 Oct 2013, at 15:58, Daniel Goertzen <<A HREF="https://lists.ninenines.eu/listinfo/extend">daniel.goertzen at gmail.com</A>>
</I>><i> wrote:
</I>><i>
</I>><i> Well, this sort of works. I tried this in the response handler:
</I>><i>
</I>><i> {ok, Req2} = cowboy_req:reply(404, [] , <<"this is the body
</I>><i> that gets used">>, Req1),
</I>><i> {<<"this body gets ignored">>, Req2, State};
</I>><i>
</I>><i>
</I>><i>
</I>><i> The client receives a 404 response, but cowboy crashes:
</I>><i>
</I>><i> =ERROR REPORT==== 8-Sep-2013::22:22:03 ===
</I>><i> Error in process <0.131.0> with exit value:
</I>><i> {function_clause,[{cowboy_req,reply,[200,[],<<31
</I>><i> bytes>>,{http_req,#Port<0.1208>,ranch_tcp,keepalive,<0.131.0>,<<3
</I>><i> bytes>>,'HTTP/1.1',{{192,168,1,187},51017},<<12 bytes>>,undefined,80,<<24
</I>><i> bytes>>,undefined,<<0 bytes>>,undefined,[{channel_num,3}],[{<<10
</I>><i> bytes>>,<<11 bytes>>},{<<4 bytes>>,<<12 bytes>>},{<<6 bytes>>,<<3
</I>><i> bytes>>}],[{<<17 bytes>>,undefined},{<<13 bytes>>,undefined},{<<19
</I>><i> bytes>>,undefined},{<<8 bytes>>,undefined},{<<6 bytes>>,[...
</I>><i>
</I>><i>
</I>><i>
</I>><i> The issue is that the REST wrapper wants to do the cowboy_req:reply(), and
</I>><i> when we do the call we cause the wrapper's call to fail.
</I>><i>
</I>><i> Dan.
</I>><i>
</I>><i>
</I>><i>
</I>><i> On Tue, Oct 29, 2013 at 4:01 PM, Ivan uemlianin <<A HREF="https://lists.ninenines.eu/listinfo/extend">ivan at llaisdy.com</A>> wrote:
</I>><i>
</I>>><i> Sorry for terse but I only have a phone. Why can't you return a 404 here?
</I>>><i> Using something like cowboy:reply(404, ...
</I>>><i>
</I>>><i> Ivan
</I>>><i>
</I>>><i> --
</I>>><i> festina lente
</I>>><i>
</I>>><i>
</I>>><i> On 29 Oct 2013, at 21:25, Daniel Goertzen <<A HREF="https://lists.ninenines.eu/listinfo/extend">daniel.goertzen at gmail.com</A>>
</I>>><i> wrote:
</I>>><i>
</I>>><i> My situation is that I have a rest handler that may fail due to invalid
</I>>><i> url segments. Example situation:
</I>>><i>
</I>>><i>
</I>>><i> init(_Transport, _Req, _Opts) ->
</I>>><i> {upgrade, protocol, cowboy_rest}.
</I>>><i>
</I>>><i> content_types_provided(Req, State) ->
</I>>><i> {[{<<"application/json">>, get_json}], Req, State}.
</I>>><i>
</I>>><i> get_json(Req0, State) ->
</I>>><i> {Params, Req1} = lists:mapfoldl(fun cowboy_req:binding/2, Req0,
</I>>><i> [param1, param2, param3, ....]),
</I>>><i>
</I>>><i> case catch other_module:request(Params) of
</I>>><i> {'EXIT', {badarg, _}} ->
</I>>><i> hmmm, Params were bad and I would like to return a 404 code
</I>>><i> now.
</I>>><i> Result ->
</I>>><i> {jiffy:encode(Result), Req1, State}
</I>>><i> end.
</I>>><i>
</I>>><i>
</I>>><i>
</I>>><i> So I would like to return a 404 code when my underlying request function
</I>>><i> fails, but it appears my choices are:
</I>>><i>
</I>>><i> - return a 200 (ok) response with data.
</I>>><i> - crash and cause a 500 (Internal Server Error) response to be returned.
</I>>><i> Not exactly the sentiment I want.
</I>>><i>
</I>>><i>
</I>>><i> Is there some other way to cause a 404 response?
</I>>><i>
</I>>><i> I realize I could add path constraint functions, but I will be
</I>>><i> replicating logic from my underlying request function. Furthermore, the
</I>>><i> constraint functions consider parameters in isolation, so that won't work
</I>>><i> if the validity of parameters is coupled.
</I>>><i>
</I>>><i> Thanks,
</I>>><i> Dan.
</I>>><i>
</I>>><i> _______________________________________________
</I>>><i> Extend mailing list
</I>>><i> <A HREF="https://lists.ninenines.eu/listinfo/extend">Extend at lists.ninenines.eu</A>
</I>>><i> <A HREF="http://lists.ninenines.eu:81/listinfo/extend">http://lists.ninenines.eu:81/listinfo/extend</A>
</I>>><i>
</I>>><i>
</I>><i>
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