Switch from Unicorn to Puma

Gemfile

@@ -83,6 +83,7 @@ gem 'rack-rewrite'
 gem 'rack-ssl', require: 'rack/ssl'
 gem 'roadie-rails'
 
+gem 'puma'
 gem 'hiredis'
 gem 'redis', '>= 4.0', require: ['redis', 'redis/connection/hiredis']
 gem 'sidekiq'
@@ -128,7 +129,7 @@ gem "view_component", require: "view_component/engine"
 
 group :production, :staging do
   gem 'ddtrace'
-  gem 'unicorn-worker-killer'
+  gem 'sd_notify' # For better Systemd process management. Used by Puma.
 end
 
 group :test, :development do
@@ -148,7 +149,6 @@ group :test, :development do
   gem 'selenium-webdriver'
   gem 'shoulda-matchers'
   gem 'timecop'
-  gem 'unicorn-rails'
   gem 'webdrivers'
   gem 'cuprite'
 end

Gemfile.lock

@@ -319,8 +319,6 @@ GEM
       rspec-core (~> 3.0)
       ruby-progressbar (~> 1.4)
     geocoder (1.6.7)
-    get_process_mem (0.2.7)
-      ffi (~> 1.0)
     globalid (0.4.2)
       activesupport (>= 4.2.0)
     gmaps4rails (2.1.2)
@@ -355,7 +353,6 @@ GEM
       multi_json (~> 1.0)
       rspec (>= 2.0, < 4.0)
     jwt (2.2.3)
-    kgio (2.11.3)
     knapsack (3.1.0)
       rake
     launchy (2.5.0)
@@ -435,6 +432,8 @@ GEM
       byebug (~> 11.0)
       pry (~> 0.13.0)
     public_suffix (4.0.6)
+    puma (5.3.2)
+      nio4r (~> 2.0)
     raabro (1.4.0)
     racc (1.5.2)
     rack (2.2.3)
@@ -484,7 +483,6 @@ GEM
       rake (>= 0.13)
       thor (~> 1.0)
     rainbow (3.0.0)
-    raindrops (0.19.1)
     rake (13.0.3)
     ransack (2.4.2)
       activerecord (>= 5.2.4)
@@ -575,6 +573,7 @@ GEM
       sprockets (>= 2.8, < 4.0)
       sprockets-rails (>= 2.0, < 4.0)
       tilt (>= 1.1, < 3)
+    sd_notify (0.1.1)
     selenium-webdriver (3.142.7)
       childprocess (>= 0.5, < 4.0)
       rubyzip (>= 1.2.2)
@@ -632,15 +631,6 @@ GEM
     uglifier (4.2.0)
       execjs (>= 0.3.0, < 3)
     unicode-display_width (2.0.0)
-    unicorn (6.0.0)
-      kgio (~> 2.6)
-      raindrops (~> 0.7)
-    unicorn-rails (2.2.1)
-      rack
-      unicorn
-    unicorn-worker-killer (0.4.5)
-      get_process_mem (~> 0)
-      unicorn (>= 4, < 7)
     uniform_notifier (1.14.2)
     valid_email2 (4.0.0)
       activemodel (>= 3.2)
@@ -769,6 +759,7 @@ DEPENDENCIES
   pg (~> 1.2.3)
   pry (~> 0.13.0)
   pry-byebug (~> 3.9.0)
+  puma
   rack-mini-profiler (< 3.0.0)
   rack-rewrite
   rack-ssl
@@ -788,6 +779,7 @@ DEPENDENCIES
   rubocop
   rubocop-rails
   sass-rails (< 5.1.0)
+  sd_notify
   select2-rails!
   selenium-webdriver
   shoulda-matchers
@@ -803,8 +795,6 @@ DEPENDENCIES
   test-unit (~> 3.4)
   timecop
   uglifier (>= 1.0.3)
-  unicorn-rails
-  unicorn-worker-killer
   valid_email2
   view_component
   view_component_storybook

config.ru

@@ -2,18 +2,5 @@
 
 # This file is used by Rack-based servers to start the application.
 
-if ENV.fetch('KILL_UNICORNS', false) && ['production', 'staging'].include?(ENV['RAILS_ENV'])
-  # Gracefully restart individual unicorn workers if they have:
-  # - performed between 25000 and 30000 requests
-  # - grown in memory usage to between 700 and 850 MB
-  require 'unicorn/worker_killer'
-  use Unicorn::WorkerKiller::MaxRequests,
-      ENV.fetch('UWK_REQS_MIN', 25_000).to_i,
-      ENV.fetch('UWK_REQS_MAX', 30_000).to_i
-  use Unicorn::WorkerKiller::Oom,
-      ( ENV.fetch('UWK_MEM_MIN', 700).to_i * (1024**2) ),
-      ( ENV.fetch('UWK_MEM_MAX', 850).to_i * (1024**2) )
-end
-
 require ::File.expand_path('config/environment', __dir__)
 run Openfoodnetwork::Application