Puma: change config to enable cluster mode in production

config/puma.rb

@@ -15,42 +15,43 @@ port        ENV.fetch("PORT") { 3000 }
 #
 environment ENV.fetch("RAILS_ENV") { "development" }
 
-# Specifies the number of `workers` to boot in clustered mode.
-# Workers are forked webserver processes. If using threads and workers together
-# the concurrency of the application would be max `threads` * `workers`.
-# Workers do not work on JRuby or Windows (both of which do not support
-# processes).
-#
-# workers ENV.fetch("WEB_CONCURRENCY") { 2 }
+if ENV.fetch("RAILS_ENV") == "production"
+  # Specifies the number of `workers` to boot in clustered mode.
+  # Workers are forked webserver processes. If using threads and workers together
+  # the concurrency of the application would be max `threads` * `workers`.
+  # Workers do not work on JRuby or Windows (both of which do not support
+  # processes).
+  #
+  workers ENV.fetch("WEB_CONCURRENCY") { 2 }
 
-# Use the `preload_app!` method when specifying a `workers` number.
-# This directive tells Puma to first boot the application and load code
-# before forking the application. This takes advantage of Copy On Write
-# process behavior so workers use less memory. If you use this option
-# you need to make sure to reconnect any threads in the `on_worker_boot`
-# block.
-#
-# preload_app!
+  # Use the `preload_app!` method when specifying a `workers` number.
+  # This directive tells Puma to first boot the application and load code
+  # before forking the application. This takes advantage of Copy On Write
+  # process behavior so workers use less memory. If you use this option
+  # you need to make sure to reconnect any threads in the `on_worker_boot`
+  # block.
+  #
+  preload_app!
 
-# If you are preloading your application and using Active Record, it's
-# recommended that you close any connections to the database before workers
-# are forked to prevent connection leakage.
-#
-# before_fork do
-#   ActiveRecord::Base.connection_pool.disconnect! if defined?(ActiveRecord)
-# end
+  # If you are preloading your application and using Active Record, it's
+  # recommended that you close any connections to the database before workers
+  # are forked to prevent connection leakage.
+  #
+  before_fork do
+    ActiveRecord::Base.connection_pool.disconnect! if defined?(ActiveRecord)
+  end
 
-# The code in the `on_worker_boot` will be called if you are using
-# clustered mode by specifying a number of `workers`. After each worker
-# process is booted, this block will be run. If you are using the `preload_app!`
-# option, you will want to use this block to reconnect to any threads
-# or connections that may have been created at application boot, as Ruby
-# cannot share connections between processes.
-#
-# on_worker_boot do
-#   ActiveRecord::Base.establish_connection if defined?(ActiveRecord)
-# end
-#
+  # The code in the `on_worker_boot` will be called if you are using
+  # clustered mode by specifying a number of `workers`. After each worker
+  # process is booted, this block will be run. If you are using the `preload_app!`
+  # option, you will want to use this block to reconnect to any threads
+  # or connections that may have been created at application boot, as Ruby
+  # cannot share connections between processes.
+  #
+  on_worker_boot do
+    ActiveRecord::Base.establish_connection if defined?(ActiveRecord)
+  end
+end
 
 # Allow puma to be restarted by `rails restart` command.
 plugin :tmp_restart