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From: Paul Davis <paul.joseph.davis@gmail.com>
Date: Wed, 28 Oct 2009 16:20:55 -0400
Message-ID: <e2111bbb0910281320r4ae5d87ev8c5ee1543fcdbfd0@mail.gmail.com>
Subject: Re: Erlang-only CouchDB
To: user@couchdb.apache.org
Content-Type: text/plain; charset=ISO-8859-1

Zoltan, (Got the A right!)

On Wed, Oct 28, 2009 at 4:06 PM, Zoltan Lajos Kis <kiszl@tmit.bme.hu> wrote:
> Hello all,
>
> Has anyone been experimenting with running CouchDB as an Erlang only
> application? What I would love to have is:
> - stick CouchDB into my lib/ directory, and have it run as part of my
> release (everything running in a single Erlang VM).

We've done some work to make CouchDB startable via application:start()
as per Erlang semantics. This should work in theory but there still
might be gotchyas with the base install. I know people have
successfully run it as a dependent app though.

> - use Erlang views only (is erlview running within the same VM? is it
> up-to-date with CouchDB features?)

Native Erlang views can be enabled with a config option. They're in
trunk now and will remain consistent with the JavaScript server
implementation.

> - access CouchDB via an Erlang interface (is hovercraft still running? does
> it support all features available via http?)

Not sure if Hovercraft is up to date with trunk. I think I heard
someone on IRC say there was a minor version difference that was minor
to resolve.

> - no dependency on ICU, curl and SpiderMonkey (as I would not need them for
> anything)

To remove the ICU dependency you'll have to patch CouchDB because its
a linked in driver that's required for collation regardless of view
server.

Curl and Spidermonkey could be removed as install time dependencies
fairly easily by discarding couchjs after a build and updating the
configuration to not attempt to use it. I think some parts of the auth
code depend on having the JS view server available but you could ixnay
that pretty easily by giving it an Erlang implementation. Its a pretty
simple view IIRC.

For build time dependencies, I don't foresee removing them. Though I
could be convinced if the patch to the build system isn't overly
intrusive.

> Any pointers to references, case studies, whatever is much appreciated!
>
> Regards,
> ZoltAn.

I've heard of people running as a subordinate in a VM but have no
direct experience myself. As I recall they basically built CouchDB and
then installed into their Erlang package for distribution. Or some
such. It  may take a bit of effort as its not use case that's had lots
of patches submitted.

HTH,
Paul Davis