[erlang-questions] Deploying multiple webapps

[Michael Truog]

On 12/16/2015 12:31 PM, Hugo Mills wrote:
>     Hi, Loïc,
>
> On Wed, Dec 16, 2015 at 01:21:09AM +0100, Loïc Hoguin wrote:
>> I have been working on RabbitMQ these past few months, and one of
>> the tasks I got assigned was to switch the Web components from
>> Webmachine to Cowboy.
>>
>> RabbitMQ already had a way to have different services on different
>> URLs running under the same port, as you describe. So my work was in
>> part to make it work with Cowboy.
>>
>> I didn't have to change much.
>>
>> I made a tiny middleware that queries the RabbitMQ component keeping
>> tracks of all the services, that then returns with the 'dispatch'
>> environment variable added. This middleware runs just before the
>> cowboy_router middleware: https://github.com/rabbitmq/rabbitmq-web-dispatch/blob/rabbitmq-management-63/src/rabbit_cowboy_middleware.erl#L27
>>
>> The process keeping tracks of all services simply has a mapping from
>> /service1/ to the service's dispatch list (/service1/ is added
>> dynamically).
>>
>> This works pretty well, is all on one node, one port, just like you
>> need, and doesn't require much code. I suppose it wouldn't be too
>> difficult to extract and make it its own project, if that's
>> something people need.
>>
>> Note that everything I talk about here has not been merged yet; but
>> I'm getting close to completion (all tests pass, yada yada).
>     It sounds like it would be a big part of a solution of what I'd
> like to do.
>
>     I guess another analogy of what I'm trying to do is that it's very
> like a Java Servlet container: something that I can drop services
> into, where the container handles the main HTTP serving and holds the
> configuration of which services it runs, where I don't have to
> recompile, rebuild or redeploy the container to alter the set of
> services running in it.

CloudI provides a service abstraction for fault-tolerant messaging utilizing
the Erlang VM.  The problem you are describing is part of the quickstart at
http://cloudi.org/#Erlang .

CloudI supports non-Erlang programming languages, providing the same
service abstraction, but you can use it for Erlang-only services
(use the https://github.com/CloudI/cloudi_core/ repository to get only the
  Erlang/Elixir support).  If you need to compare this to RabbitMQ, look at
http://cloudi.org/faq.html#1_Messaging .  An Erlang-only example that
provides a bit more information than the quickstart is at
https://github.com/CloudI/CloudI/tree/develop/examples/hello_world5
if you choose to embed CloudI services into an Erlang OTP application
hierarchy (otherwise you would be using the CloudI configuration file
to have an explicit startup order).