ActionCable Postgres adapter is ActiveRecord-specific

[bgentry]

Steps to reproduce

1. Create a Rails app using Sequel and sequel-rails, without ActiveRecord
2. Attempt to use the ActionCable Postgres adapter
3. Watch it crash trying to autoload ActiveRecord

Expected behavior

Ideally, this would support the most popular Postgres ORMs out of the box. Or at least the docs should mention that this only works with AR.

Actual behavior

Exception trying to autoload ActiveRecord

System configuration

Rails version: 5.0.0.1

Ruby version: 2.3.3

It was very easy to fork the Postgres ActionCable subscription adapter to work with Sequel. I only had to alter the with_connection method, which is even shorter with Sequel: https://gist.github.com/bgentry/5a4592dbbcc398c0ad651c53af7da51f#file-postgresql_sequel-rb-L35-L40

I'm not sure whether the right approach is to try to support this out-of-the-box, or at least to document that the adapter is AR-specific. Thoughts?

As a user I'd certainly prefer not to have to maintain a fork of the subscription adapter. But I can certainly see the argument for this not being Rails' problem. I suppose I really only need to monkey-patch or refine that one method, though, so not too bad either way.

[rafaelfranca]

That is a good point. I don't see why this code is using Active Record at all, it should not, even more that actioncable doesn't depend on activerecord and active record base is not being required in that file.

In my opinion we should use the pg connection directly.

[bgentry]

@rafaelfranca my guess is it's because it's piggybacking on the AR database config logic. An alternative approach to supporting any ORM is to have a config setting that lets me specify how to get a new PG connection, defaulting to the AR method used currently.

I did notice the lack of a require at the top which is maybe a separate but related issue?

[rafaelfranca]

I prefer to use the connection directly over supporting different ORM. There is no need for a ORM in actioncable.

We can't add the require without changing the dependencies of actioncable to add activerecord, so I prefer that we solve this issue removing any orm specific code.

[maclover7]

Thank you for opening up this issue! Working on a solution locally now.

[maclover7]

Opened up #27216 as a possible solution for this.

[KarimElsayad247]

This issue remains open after... 6 years! RailsGuides still mention this behavior might be changed

[reiz]

I would like to use it together with MongoID. I have already a MongoDB cluster on production and I would like to avoid adding Redis, because of different reasons.

[dbackeus]

I've released a rubygem which enhances the Postgres adapter, making it possible to bypass the ActiveRecord dependency by adding explicit url configuration. It also fixes the 8000 byte payload size limit.

Rubygem: https://rubygems.org/gems/actioncable-enhanced-postgresql-adapter
Documentation: https://github.com/reclaim-the-stack/actioncable-enhanced-postgresql-adapter#readme

[washu]

I written one that uses mongoid.
I have a not tested yet mongoid, subscription adapter. but can you send you a gist

[washu]

https://gist.github.com/washu/a2b5415e7b9a538fe782d32ff5bb9109

I just wrapped some code i had in my own crystal/anycable type bridge