How can I serve requests concurrently with Rails 4?

Question

I\'m trying to serve multiple requests concurrently in Rails 4, something I was able to do very easily with config.threadsafe! and Puma in Rails 3.

Answer 1

It seems that by default, in Rails 4, concurrent requests are not enabled in the Development environment.

I found this quote in the documentation.

Rack::Lock wraps the app in mutex so it can only be called by a single thread at a time. Only enabled when config.cache_classes is false.

Which means that if config.cache_classes = false (which it is by default in dev env) we can't have concurrent requests.

Concurrent requests do work with my example in production environment.

One solution is to set config.cache_classes = true in the development environment, but then the code doesn't reload on a change, which doesn't really work for development.

The second kind of hacky solution is to disable the Rack::Lock middleware in development.

So if you were to add in development.rb the following line:

config.middleware.delete Rack::Lock

you should be able to have concurrent requests in development environment with cache classes disabled.