Add Puma config for "staging" env

config/puma/staging.rb

@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+root_dir = File.expand_path '../..', __dir__
+
+workers_count = ENV.fetch('WEB_CONCURRENCY') { 1 }
+threads_count = ENV.fetch('RAILS_MAX_THREADS') { 5 }
+
+# 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 workers_count
+
+# Puma can serve each request in a thread from an internal thread pool.
+# The `threads` method setting takes two numbers: a minimum and maximum.
+# Any libraries that use thread pools should be configured to match
+# the maximum value specified for Puma. Default is set to 5 threads for minimum
+# and maximum; this matches the default thread size of Active Record.
+#
+threads threads_count, threads_count
+
+# 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.
+#
+# preload_app!
+
+# Bind the server to "url". "tcp://", "unix://" and "ssl://" are the only
+# accepted protocols.
+#
+bind "unix://#{File.join(root_dir, 'tmp', 'sockets', 'puma.sock')}"
+
+# Allow puma to be restarted by `rails restart` command.
+# plugin :tmp_restart
+
+# Use "path" as the file to store the server info state. This is
+# used by "pumactl" to query and control the server.
+#
+state_path File.join(root_dir, 'tmp', 'pids', 'puma.state')