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From: Robert Dionne <dionne@dionne-associates.com>
Subject: Re: Building Erlang app around CouchDB
Date: Wed, 22 Apr 2009 17:09:54 -0400
To: user@couchdb.apache.org

I'm not quite sure what it is you are trying to do but it seems like =20
you don't need the ecouch in the middle if you're already using =20
MochiWeb.

Anyway I put together an erlang client for some testing[1] that is =20
implemented as a gen_server and uses either inets or ibrowse. Feel =20
free to push it along if it's useful to you. It evolved from another=20
[2], which has been discontinued.

Cheers,

Bob

[1] http://github.com/bdionne/erl-couch/tree/master
[2] http://code.google.com/p/erlcouch/


On Apr 22, 2009, at 4:51 PM, David Mitchell wrote:

> OK, I think I've got two of the key pieces in place:
> - I can use MochiWeb to construct a Web framework pretty easily =20
> (note to
> self: why haven't I bothered to look at Yaws alternatives before?)
> - I can use eCouch to have MochiWeb interface with CouchDB
>
> In other words,
> Web client --> (REST call) --> MochiWeb --> eCouch --> CouchDB
> and I haven't had to go outside of Erlang
>
> I put together a very quick couple of pages today with this setup =20
> and it
> worked fine.
>
> What I'm still not seeing is a way to do XML<->JSON conversions within
> Erlang.  Are there libraries out there that do this, or do I have =20
> to resort
> to something like JavaScript (or try to come up with my own Erlang-=20
> based
> solution)?
>
> Thanks in advance
>
> Dave M.
>
>
>
> 2009/4/21 Noah Slater <nslater@apache.org>
>
>> On Tue, Apr 21, 2009 at 09:16:37PM +1000, David Mitchell wrote:
>>> I want to be able to build an application around CouchDB that =20
>>> lets me
>> load
>>> in XML documents (i.e. converting XML to JSON within Erlang, =20
>>> rather than
>> via
>>> e.g. a Rails application talking to CouchDB).  I also want to be =20
>>> able to
>>> extract data from CouchDB as XML documents, again doing all the
>> JSON<->XML
>>> conversion within Erlang rather than a separate language.  The whole
>> thing
>>> should work as a Web service (either REST or SOAP would be fine, =20
>>> although
>> I
>>> imagine REST should be easier as CouchDB itself has a REST =20
>>> interface).
>>
>> This sounds like a good opportunity to work with the grain of =20
>> CouchDB and
>> HTTP.
>>
>>  By eschewing shared state, and enforcing a uniform interface, we =20
>> restrict
>>  components from =93seeing=94 beyond the context of an individual =20
>> request. This
>>  introduces a =93pipe and filter=94 style property to the system, =20
>> where access
>> or
>>  functionality can be added, modified, or restricted transparently =20=

>> between
>>  client and server.
>>
>>  Common features such as authentication, authorization, caching,
>> compression,
>>  partitioning, proxying, tunneling, encryption or URI rewriting are
>> possible by
>>  placing standard applications such as Apache httpd or nginx in =20
>> front of
>> your
>>  server. You=92re free to augment, adapt or limit your setup as you =20=

>> see fit.
>>  Figure 1-7 shows an example configuration of layered Web =20
>> architecture.
>>
>>  Need some caching? Just throw in a cache between your server and =20
>> clients.
>> Need
>>  some load balancing or authentication? Just throw in a reverse =20
>> proxy.
>>
>>      - Layered System, CouchDB: TDG,
>> http://books.couchdb.org/relax/why-couchdb
>>
>> Need media type conversion? Throw in a proxy!
>>
>>  Intermediary components act as both a client and a server in =20
>> order to
>> forward,
>>  with possible translation, requests and responses. A proxy =20
>> component is an
>>  intermediary selected by a client to provide interface =20
>> encapsulation of
>> other
>>  services, data translation, performance enhancement, or security
>> protection.
>>
>>        -
>> http://www.ics.uci.edu/~fielding/pubs/dissertation/=20
>> rest_arch_style.htm<http://www.ics.uci.edu/%7Efielding/pubs/=20
>> dissertation/rest_arch_style.htm>
>>
>> See Figure 5-10, ibid.
>>
>> Best,
>>
>> --
>> Noah Slater, http://tumbolia.org/nslater
>>