Run puma workers in Production, but not in Development - ruby-on-rails

Question

I'm running the following puma config
threads_count = Integer(ENV["DB_POOL"] || ENV["MAX_THREADS"] || 15)
threads threads_count, threads_count
workers 3
preload_app!
rackup DefaultRackup
port ENV["PORT"] || 3000
environment ENV["RACK_ENV"] || "development"
on_worker_boot do
ActiveSupport.on_load(:active_record) do
ActiveRecord::Base.establish_connection
end
end
before_fork do
ActiveRecord::Base.connection_pool.disconnect!
end
It's great for production, but I don't want to spin up 3 workers or use webrick in development. I tried wrapping the worker specific code in an environment check, but that breaks the puma DSL. Any ideas for running puma in non-clustered mode in development?

Answer 1

Rails is not defined in puma config file, so Rails.env can't be used here, but RACK_ENV is ok.
workers(ENV["RACK_ENV"] == "production" ? 3 : 0)

Answer 2

I figure out a working solution before seeing scorix's answer which I accepted, but I ended up with a slightly different solution. This allows you to set the worker count, so I can run 1 in staging and 3 in production for example.
threads_count = Integer(ENV["DB_POOL"] || ENV["MAX_THREADS"] || 15)
threads threads_count, threads_count
rackup DefaultRackup
port ENV["PORT"] || 3000
environment ENV["RACK_ENV"] || "development"
if ENV["RACK_ENV"] == "production"
workers ENV.fetch("WEB_CONCURRENCY") { 3 }
preload_app!
ActiveSupport.on_load(:active_record) do
ActiveRecord::Base.establish_connection
end
before_fork do
ActiveRecord::Base.connection_pool.disconnect!
end
end

Answer 3

Check out the Configuration part on the docs.
What I did was set up the production config on config/puma/production.rb, so on production you would run puma with puma -C config/puma/production.rb (or however you run it on prod) and on development, rails server won't use that configuration