Add unicorn config.

config/unicorn.rb

@@ -0,0 +1,27 @@
+if ENV["RAILS_ENV"] == "development"
+  worker_processes 1
+else
+  worker_processes Integer(ENV["WEB_CONCURRENCY"] || 3)
+end
+
+timeout 15
+preload_app true
+
+before_fork do |_server, _worker|
+  Signal.trap 'TERM' do
+    puts 'Unicorn master intercepting TERM and sending myself QUIT instead'
+    Process.kill 'QUIT', Process.pid
+  end
+
+  defined?(ActiveRecord::Base) &&
+    ActiveRecord::Base.connection.disconnect!
+end
+
+after_fork do |_server, _worker|
+  Signal.trap 'TERM' do
+    puts 'Unicorn worker intercepting TERM and doing nothing. Wait for master to send QUIT'
+  end
+
+  defined?(ActiveRecord::Base) &&
+    ActiveRecord::Base.establish_connection
+end