Unicorn configuration for deploying application to production with capistrano

Capfile

# frozen_string_literal: true

# Load DSL and set up stages
require 'capistrano/setup'

# Include default deployment tasks
require 'capistrano/deploy'
require 'capistrano/rvm'
require 'capistrano/bundler'
require 'capistrano/rails'
# require 'capistrano/passenger'
require 'capistrano3/unicorn'
require 'whenever/capistrano'

require 'capistrano/sidekiq'
install_plugin Capistrano::Sidekiq
install_plugin Capistrano::Sidekiq::Systemd

# Load the SCM plugin appropriate to your project:
require 'capistrano/scm/git'
install_plugin Capistrano::SCM::Git

# Load custom tasks from `lib/capistrano/tasks` if you have any defined
Dir.glob('lib/capistrano/tasks/*.rake').each { |r| import r }

deploy.rb

# config/deploy.rb

# frozen_string_literal: true

# config valid for current version and patch releases of Capistrano
lock '~> 3.16.0'

set :application, 'qna'
set :repo_url, 'git@github.com:georgiybykov/qna.git'

# Default deploy_to directory is /var/www/my_app_name
set :deploy_to, '/home/deploy/qna'
set :deploy_user, 'deploy'

set :pty, false

# Default value for :linked_files is []
append :linked_files, 'config/database.yml', 'config/master.key', 'config/elasticsearch.yml', '.env.production'

# Default value for linked_dirs is []
append :linked_dirs, 'log', 'tmp/pids', 'tmp/cache', 'tmp/sockets', 'public/system', 'storage'

after 'deploy:publishing', 'deploy:restart'

namespace :deploy do
  task :restart do
    invoke 'unicorn:restart'
  end
end

Gemfile

...
# App server for production
gem 'unicorn'
...

group :development do
  ...
  # Adds specific tasks for Capistrano
  ...
  gem 'capistrano3-unicorn', require: false
  ...
end

production.rb

# config/unicorn/production.rb

# frozen_string_literal: true

# paths
app_path = '/home/deploy/qna'
working_directory "#{app_path}/current"
pid               "#{app_path}/current/tmp/pids/unicorn.pid"

# listen
listen "#{app_path}/shared/tmp/sockets/unicorn.qna.sock", backlog: 64

# logging
stderr_path 'log/unicorn.stderr.log'
stdout_path 'log/unicorn.stdout.log'

# workers
worker_processes 3

# use correct Gemfile on restarts
before_exec do |_server|
  ENV['BUNDLE_GEMFILE'] = "#{app_path}/current/Gemfile"
end

# preload
preload_app true

before_fork do |server, _worker|
  # the following is highly recommended for Rails + "preload_app true"
  # as there's no need for the master process to hold a connection
  ActiveRecord::Base.connection.disconnect! if defined?(ActiveRecord::Base)

  # Before forking, kill the master process that belongs to the .oldbin PID.
  # This enables 0 downtime deploys.
  old_pid = "#{server.config[:pid]}.oldbin"
  if File.exist?(old_pid) && server.pid != old_pid
    begin
      Process.kill('QUIT', File.read(old_pid).to_i)
    rescue Errno::ENOENT, Errno::ESRCH
      # someone else did our job for us
    end
  end
end

after_fork do |_server, _worker|
  ActiveRecord::Base.establish_connection if defined?(ActiveRecord::Base)
end

qna.conf

# /etc/nginx/sites-enabled/qna.conf

upstream unicorn {
  server unix:/home/deploy/qna/shared/tmp/sockets/unicorn.qna.sock fail_timeout=0;
}

server {
  listen 80;
  listen [::]:80;

  server_name 65.108.50.164;
  root /home/deploy/qna/current/public;
  client_max_body_size 20M;

  # passenger_enabled on;

  location ^~ /assets/ {
                gzip_static on;
                expires max;
                add_header Cache-Control public;
        }

  try_files $uri/index.html $uri @unicorn;
  location @unicorn {
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_redirect off; 
    proxy_pass http://unicorn;
  }
}

For more information look at the changes at the pull request here: georgiybykov/qna#24