Files to configure puma + nginx for simple rails deployment. Put them under config folder.

deploy.rb

require "bundler/capistrano"
require "puma/capistrano"

server "<server_ip>", :web, :app, :db, primary: true

set :application, "<app_name>"
set :user, "deployer"
set :deploy_to, "/home/#{user}/apps/#{application}"
set :deploy_via, :remote_cache
set :use_sudo, false

set :scm, "git"
set :repository, "git@github.com:bruno-campos/#{application}.git"
set :branch, "master"

default_run_options[:pty] = true
#ssh_options[:auth_methods] = ["publickey"]
ssh_options[:forward_agent] = true
ssh_options[:keys] = ["~/.ssh/formfookey.pem"]

after "deploy", "deploy:cleanup" # keep only the last 5 releases

namespace :deploy do

  task :setup_config, roles: :app do
    sudo "ln -nfs #{current_path}/config/nginx.conf /etc/nginx/sites-enabled/#{application}"
    sudo "ln -nfs #{current_path}/config/puma_init.sh /etc/init.d/puma_#{application}"
    sudo "chmod +x /etc/init.d/puma_#{application}"
    run "mkdir -p #{shared_path}/config"
    run "mkdir -p #{shared_path}/sockets"
    run "mkdir -p #{shared_path}/pids"
  end
  after "deploy:setup", "deploy:setup_config"

  task :symlink_config, roles: :app do
    run "ln -nfs #{shared_path}/config/puma.rb #{release_path}/config/puma.rb"
  end
  after "deploy:finalize_update", "deploy:symlink_config"

  desc "Make sure local git is in sync with remote."
  task :check_revision, roles: :web do
    unless `git rev-parse HEAD` == `git rev-parse origin/#{branch}`
      puts "WARNING: HEAD is not the same as origin/#{branch}"
      puts "Run `git push` to sync changes."
      exit
    end
  end
  before "deploy", "deploy:check_revision"
end

nginx.conf

upstream puma {
  server unix:/home/deployer/apps/<app_name>/shared/sockets/puma.sock;
}

server {
  listen 80 default deferred;
  # server_name example.com;
  root /home/deployer/apps/<app_name>/current/public;

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

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

  error_page 500 502 503 504 /500.html;
  client_max_body_size 4G;
  keepalive_timeout 10;
}

puma.rb

rails_env = Rails.env || 'production'

threads 1,16

bind  "unix:///data/apps/<app_name>/shared/sockets/puma.sock"
pidfile "/data/apps/<app_name>/shared/pids/puma.pid"
state_path "/data/apps/<app_name>/shared/sockets/puma.state"

activate_control_app

puma_init.sh

set -e

# Feel free to change any of the following variables for your app:
APP_ROOT=/home/deployer/apps/<app_name>/
CMD="cd $APP_ROOT/current; bundle exec puma -C $APP_ROOT/shared/config/puma.rb -b unix://$APP_ROOT/shared/sockets/puma.sock -e production --control unix://$APP_ROOT/shared/sockets/pumactl.sock --state $APP_ROOT/shared/sockets/puma.state --pidfile $APP_ROOT/shared/pids/puma.pid 2>&1 >> $APP_ROOT/shared/log/puma.log &"
CTL="cd $APP_ROOT/current; bundle exec pumactl -S $APP_ROOT/shared/sockets/puma.state"
AS_USER=deployer
set -u

run () {
  if [ "$(id -un)" = "$AS_USER" ]; then
    eval $1
  else
    su -c "$1" - $AS_USER
  fi
}

case "$1" in
start)
  if [ ! -e "$APP_ROOT/shared/sockets/puma.sock" ]
  then
    run "$CMD"
    exit 1
  else
    echo >&2 "Already running"
  fi
  ;;
stop)
  [ -e "$APP_ROOT/shared/sockets/puma.sock" ]  && run "$CTL stop" && exit 0
  echo >&2 "Not running"
    ;;
force-stop)
  [ -e "$APP_ROOT/shared/sockets/puma.sock" ]  && run "$CTL halt" && exit 0
  echo >&2 "Not running"
  ;;
restart|reload)
  [ -e "$APP_ROOT/shared/sockets/puma.sock" ]  && run "$CTL restart" && exit 0
  echo >&2 "Couldn't reload, starting '$CMD' instead"
  run "$CMD"
  ;;
*)
  echo >&2 "Usage: $0 <start|stop|restart|force-stop>"
  exit 1
  ;;
esac