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Oliveira</B> + <A HREF="mailto:extend%40lists.ninenines.eu?Subject=Re%3A%20%5B99s-extend%5D%20REST%20responses&In-Reply-To=%3CCA%2BdV7cTrbQd-widnjH5CjsYum%3DASwax7VxtAUn_9BVONp2MMuA%40mail.gmail.com%3E" + TITLE="[99s-extend] REST responses">paulo.ferraz.oliveira at gmail.com + </A><BR> + <I>Tue May 20 23:41:15 CEST 2014</I> + <P><UL> + <LI>Previous message: <A HREF="000386.html">[99s-extend] REST responses +</A></li> + <LI>Next message: <A HREF="000389.html">[99s-extend] REST responses +</A></li> + <LI> <B>Messages sorted by:</B> + <a href="date.html#388">[ date ]</a> + <a href="thread.html#388">[ thread ]</a> + <a href="subject.html#388">[ subject ]</a> + <a href="author.html#388">[ author ]</a> + </LI> + </UL> + <HR> +<!--beginarticle--> +<PRE>Hi, Loïc. + +Thanks for having taken the time to reply. In some of my questions I think +I didn't explain myself correctly so I'll give it another go. + + +On 20 May 2014 19:46, Loïc Hoguin <<A HREF="https://lists.ninenines.eu/listinfo/extend">essen at ninenines.eu</A>> wrote: + +><i> Hi, +</I>><i> +</I>><i> +</I>><i> On 05/20/2014 06:27 PM, Paulo F. Oliveira wrote: +</I>><i> +</I>>><i> Hello. +</I>>><i> +</I>>><i> First of all, thanks for the great work you've done with cowboy. I've +</I>>><i> been using it with a fait amount of success and I'm a fairly new Erlang +</I>>><i> developer. I'm mainly interested in the REST "interface" of the +</I>>><i> application and its way of doing RESTful things, and I like the way you +</I>>><i> did it (what with all the content_types_provided, service_available, +</I>>><i> etc. functions). I've tested the way the system reacted to the different +</I>>><i> Accept, Content-Type, etc. headers and always got very well-opinionated +</I>>><i> responses (406, 415, ...). +</I>>><i> +</I>>><i> A couple of questions remain though (I'm sorry if they've been asked +</I>>><i> already but I've searched the web for answers and read the available +</I>>><i> docs and couldn't find them): +</I>>><i> +</I>>><i> 1. is it expected that, if I use cowboy_req:reply/2 in a GET handler +</I>>><i> (coming from content_types_provided), the onresponse/4 hook be called +</I>>><i> twice? I guess one is due to the reply and the other one due to the +</I>>><i> workflow of the request, but is there a way to prevent the second +</I>>><i> execution? +</I>>><i> +</I>><i> +</I>><i> If you reply from a callback you must call {halt, Req, State} to stop +</I>><i> processing. +</I> + +Got it! + + +><i> 2. if I want to JSON-parse ALL my requests should I a) use the +</I>>><i> onrequest/1 hook or b) do this on a per-request basis? Because I'd like +</I>>><i> to reply with a 400 ASAP but keep going if the JSON validates (I'm going +</I>>><i> to use JSON-schema for validating input); and, if possible, have the +</I>>><i> JSON-parsed body stored somewhere for future manipulation. +</I>>><i> +</I>><i> +</I>><i> It makes little sense to do it before the accept callback you define. Not +</I>><i> only because you will duplicate content-type checks and whatnot, but also +</I>><i> because you don't actually win anything from doing this. If you are using +</I>><i> JSON, then JSON processing will take infinitely more resources than the +</I>><i> REST code. +</I> + +OK, I'll probably stick with a "helper" function that'll do this for me and +reply in case there are validation errors. +I only found the flow diagrams for the requests today after I had sent this +message, and they helped a lot. + + +><i> 3. I haven't seen examples that made use of the State (from the function +</I>>><i> returns). When should I use this instead of the Request metadata? I'd +</I>>><i> like to be able to set a generic error state for a request (either in +</I>>><i> meta ou State) and that have a "standard" error response be created at a +</I>>><i> later time (in a unique function, for example - e.g. onresponse/4). +</I>>><i> +</I>><i> +</I>><i> State is for the functions within the current module. Look at +</I>><i> cowboy_static for an example. +</I> + +State allows me to, well, keep state, for a request "travelling" through +functions, right, and I can change it whenever I want just before returning +from a function that is executed prior to another one (the only function +for which this doesn't seem to make since is the last one cowboy calls +before actually replying to the client)? At the same time, so does the +request meta, from what I understood from the manual. So what is the +difference between one and the other and when would you recommend one or +the other. + +4. is there anything like a catch-all exception handler? I'd like to +>><i> catch exceptions that occur anywhere so I could log them and analyze +</I>>><i> them at a later moment. +</I>>><i> +</I>><i> +</I>><i> You can add your own error_logger handler, or use something like lager. +</I>><i> All errors end up sending a message to error_logger. +</I> + +I'll do this, thanks. + + +><i> I'm probably abusing the onresponse/onrequest hooks already, so your +</I>>><i> answers should help me clarify this. +</I>>><i> +</I>><i> +</I>><i> Sounds like it! +</I>><i> +</I>><i> Thanks. +</I>>><i> +</I>>><i> - Paulo +</I>>><i> +</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="https://lists.ninenines.eu/listinfo/extend">https://lists.ninenines.eu/listinfo/extend</A> +</I>>><i> +</I>>><i> +</I>><i> -- +</I>><i> Loïc Hoguin +</I>><i> <A HREF="http://ninenines.eu">http://ninenines.eu</A> +</I>><i> +</I> +Thanks. +-------------- next part -------------- +An HTML attachment was scrubbed... +URL: <<A HREF="http://lists.ninenines.eu/archives/extend/attachments/20140520/32454f85/attachment.html">http://lists.ninenines.eu/archives/extend/attachments/20140520/32454f85/attachment.html</A>> +</PRE> + +<!--endarticle--> + <HR> + <P><UL> + <!--threads--> + <LI>Previous message: <A HREF="000386.html">[99s-extend] REST responses +</A></li> + <LI>Next message: <A HREF="000389.html">[99s-extend] REST responses +</A></li> + <LI> <B>Messages sorted by:</B> + <a href="date.html#388">[ date ]</a> + <a href="thread.html#388">[ thread ]</a> + <a href="subject.html#388">[ subject ]</a> + <a href="author.html#388">[ author ]</a> + </LI> + </UL> + +<hr> +<a href="https://lists.ninenines.eu/listinfo/extend">More information about the Extend +mailing list</a><br> +</body></html> |