Use systemd to start and monitor puma

Puma 4 is no longer maintained, and Puma 5 removed the option to run
Puma as as daemon. That means that, in order to upgrade, we need to rely
in a process monitoring tool. We're using systemd because it's installed
by default in most (all?) operating systems running Consul Democracy on
production and it's supported by both Puma and the capistrano3-puma gem.

Using systemd means Puma will be automatically started whenever it
crashes, so we no longer need the changes done in commit 40b3c9f2c and
we can now use the default tasks configuration in capistrano3-puma and
capistrano3-delayed-job.

Since Puma is also started automatically when booting the system, we
don't need a cron job to do so anymore and can remove it from the
`schedule.rb` file.

Capfile

@@ -15,7 +15,7 @@ require "rvm1/capistrano3"
 
 require "capistrano/puma"
 install_plugin Capistrano::Puma, load_hooks: false
-install_plugin Capistrano::Puma::Daemon
+install_plugin Capistrano::Puma::Systemd
 
 #SCM: Git
 require "capistrano/scm/git"

config/deploy.rb

@@ -49,6 +49,7 @@ set :fnm_install_node_command, -> { "#{fetch(:fnm_setup_command)} && fnm use --i
 set :fnm_map_bins, %w[bundle node npm puma pumactl rake yarn]
 
 set :puma_conf, "#{release_path}/config/puma/#{fetch(:rails_env)}.rb"
+set :puma_systemctl_user, :user
 
 set :delayed_job_workers, 2
 set :delayed_job_roles, :background
@@ -57,9 +58,6 @@ set :delayed_job_monitor, true
 set :whenever_roles, -> { :app }
 
 namespace :deploy do
-  Rake::Task["delayed_job:default"].clear_actions
-  Rake::Task["puma:smart_restart"].clear_actions
-
   after "rvm1:hook", "map_node_bins"
 
   after :updating, "install_node"
@@ -68,12 +66,7 @@ namespace :deploy do
   after "deploy:migrate", "add_new_settings"
 
   after :publishing, "setup_puma"
-
-  after :published, "deploy:restart"
-  before "deploy:restart", "puma:restart"
-  before "deploy:restart", "delayed_job:restart"
-  before "deploy:restart", "puma:start"
-
+  before "puma:smart_restart", "stop_puma_daemon"
   after :finished, "refresh_sitemap"
 
   desc "Deploys and runs the tasks needed to upgrade to a new release"
@@ -81,6 +74,9 @@ namespace :deploy do
     after "add_new_settings", "execute_release_tasks"
     invoke "deploy"
   end
+
+  before "deploy:restart", "puma:smart_restart"
+  before "deploy:restart", "delayed_job:restart"
 end
 
 task :install_ruby do
@@ -169,10 +165,30 @@ end
 
 desc "Create pid and socket folders needed by puma"
 task :setup_puma do
-  on roles(:app) do
+  on roles(fetch(:puma_role)) do
     with rails_env: fetch(:rails_env) do
       execute "mkdir -p #{shared_path}/tmp/sockets; true"
       execute "mkdir -p #{shared_path}/tmp/pids; true"
     end
   end
+
+  after "setup_puma", "puma:systemd:config"
+  after "setup_puma", "puma:systemd:enable"
+end
+
+# Code adapted from the task to stop the daemon in capistrano3-puma
+desc "Stops the Puma daemon so systemd can start the Puma process"
+task :stop_puma_daemon do
+  on roles(fetch(:puma_role)) do |role|
+    within release_path do
+      with rails_env: fetch(:rails_env) do
+        if test("[ -f #{fetch(:puma_pid)} ]") &&
+           !test("systemctl --user is-active #{fetch(:puma_service_unit_name)}") &&
+           test(:kill, "-0 $( cat #{fetch(:puma_pid)} )")
+          info "Puma: stopping daemon"
+          execute :pumactl, "-S #{fetch(:puma_state)} -F #{fetch(:puma_conf)} stop"
+        end
+      end
+    end
+  end
 end

config/puma/defaults.rb

@@ -12,7 +12,6 @@ state_path "#{rails_root}/tmp/pids/puma.state"
 stdout_redirect "#{rails_root}/log/puma_access.log", "#{rails_root}/log/puma_error.log", true
 
 bind "unix://#{rails_root}/tmp/sockets/puma.sock"
-daemonize
 
 threads 0, 16
 workers 2

config/schedule.rb

@@ -40,7 +40,6 @@ every 1.day, at: "3:00 am", roles: [:cron] do
 end
 
 every :reboot do
-  command "cd #{@path} && bundle exec puma -C config/puma/#{@environment}.rb"
   # Number of workers must be kept in sync with capistrano's delayed_job_workers
   command "cd #{@path} && RAILS_ENV=#{@environment} bin/delayed_job -m -n 2 restart"
 end