How to run Rails multi-threaded in development?

Question

I am working on a multiple projects that talk to each other sometimes and I've run into an issue where app

1. A calls B (request 1, still running)
2. B calls A (request 2)
3. based on request 2's result, B responds to request 1

This requires me running multi-threaded rails in development mode.

I know I can set it up using puma or something like that but ... Isn't there really a simpler way?

I would like to avoid changing anything in the project (adding gems, config files..).

Something like rails s --multi would be nice, can't webrick just run with multiple threads or spawn more processes?

Can I perhaps install a standalone gem to do what I need and run something like thin run . -p 3?

Answer 1

The puma web server can provide multi-threading and multiple workers bound to a single local address.

1. Install the puma gem:

   bundle add puma
   

   or

   gem install puma
   

2. Add a puma configuration file at config/puma.rb:

   workers 1 # 1 worker in addition to master instance (i.e. handle 2 requests concurrently).
   preload_app!
   

3. Launch the Rails server.

   bundle exec rails s
   

   Puma automatically starts and loads in the config file at config/puma.rb.

Bump up the value for workers if you need to handle more than 2 concurrent requests at the same time.