delayed jobs: run dj workers under systemd (fix #4108).

lib/capistrano/tasks/delayed_job.rake

@@ -2,11 +2,11 @@ namespace :delayed_job do
   desc "Start delayed_job process"
   task :start do
     on roles(:worker) do
-      if test("[ -d #{current_path} ]")
-        within current_path do
-          with rails_env: fetch(:rails_env) do
-            hostname = capture("hostname").strip
-            execute :bundle, "exec", "script/delayed_job", "--queues=default,#{hostname}", "-n 8", "start"
+      within current_path do
+        with rails_env: fetch(:rails_env) do
+          fetch(:delayed_job_workers, 16).times do |n|
+            bundle = SSHKit.config.command_map[:bundle]
+            execute :"systemd-run", "--user --collect --slice delayed_job --unit delayed_job.#{n} -E RAILS_ENV=$RAILS_ENV -p WorkingDirectory=$PWD -p Restart=always #{bundle} exec script/delayed_job --queues=default run"
           end
         end
       end
@@ -16,36 +16,25 @@ namespace :delayed_job do
   desc "Stop delayed_job process"
   task :stop do
     on roles(:worker) do
-      if test("[ -d #{current_path} ]")
-        within current_path do
-          with rails_env: fetch(:rails_env) do
-            execute :bundle, "exec", "script/delayed_job", "stop"
-          end
-        end
-      end
+      execute :systemctl, "--user stop delayed_job.slice"
     end
   end
 
   desc "Restart delayed_job process"
   task :restart do
     on roles(:worker) do
-      find_and_execute_task("delayed_job:stop")
-      find_and_execute_task("delayed_job:start")
+      execute :systemctl, "--user restart delayed_job.slice"
     end
   end
 
-  desc "Kill delayed_job process"
-  task :kill do
+  desc "Show status of delayed_job process"
+  task :status do
     on roles(:worker) do
-      procs = capture("ps -A -o pid,command").split(/\r\n|\r|\n/).grep(/delayed_job/).map(&:to_i)
-
-      if procs.any?
-        execute "for i in #{procs.join(' ')} ; do kill -s TERM $i ; done"
-      end
+      # systemctl exits with status 3 if the service isn't running.
+      execute :systemctl, "--user status delayed_job.slice", raise_on_non_zero_exit: false
     end
   end
 end
 
-after "delayed_job:stop", "delayed_job:kill"
 before "deploy:started", "delayed_job:stop"
 after "deploy:published", "delayed_job:start"