Capistrano自動デプロイ時の502エラー

00:53 deploy:assets:backup_manifest
      01 mkdir -p /var/www/app_name/releases/20210502224248/assets_manifest_backup
    ✔ 01 ec2-user@xx.xxx.xxx.xxx 0.123s
      02 cp /var/www/app_name/releases/20210502224248/public/assets/.sprockets-manifest-d9815ef5061edc1f5133a83421dafb39.json /var/www/app_name/releases/20210502224248/assets_manifest_backup
    ✔ 02 ec2-user@xx.xxx.xxx.xxx 0.129s
00:54 deploy:migrate
      [deploy:migrate] Run `rake db:migrate`
00:54 deploy:migrating
      01 $HOME/.rbenv/bin/rbenv exec bundle exec rake db:migrate
    ✔ 01 ec2-user@xx.xxx.xxx.xxx 1.811s
00:56 deploy:symlink:release
      01 ln -s /var/www/app_name/releases/20210502224248 /var/www/app_name/releases/current
    ✔ 01 ec2-user@xx.xxx.xxx.xxx 0.139s
      02 mv /var/www/app_name/releases/current /var/www/app_name
    ✔ 02 ec2-user@xx.xxx.xxx.xxx 0.128s
00:56 unicorn:start
      01 $HOME/.rbenv/bin/rbenv exec bundle exec unicorn -c /var/www/app_name/current/config/unicorn.rb -E deployment -D 
    ✔ 01 ec2-user@xx.xxx.xxx.xxx 1.628s
      unicorn restarting...
      02 kill -s USR2 `cat /var/www/app_name/shared/tmp/pids/unicorn.pid`
    ✔ 02 ec2-user@xx.xxx.xxx.xxx 0.132s
00:58 deploy:cleanup
      Keeping 5 of 6 deployed releases on xx.xxx.xxx.xxx
      01 rm -rf /var/www/app_name/releases/20210501125235
    ✔ 01 ec2-user@xx.xxx.xxx.xxx 1.367s
01:00 deploy:log_revision
      01 echo "Branch master (at f36ae5f5de6da628e4f4d3f84ba5994fc505539a) deployed as release 20210502224248 by user" >> /var/www/app_name/revisions.log
    ✔ 01 ec2-user@xx.xxx.xxx.xxx 0.126s

app_path = File.expand_path('../../../', __FILE__)

worker_processes 1

working_directory "#{app_path}/current" 

pid "#{app_path}/shared/tmp/pids/unicorn.pid" 

listen "#{app_path}/shared/tmp/sockets/unicorn.sock"

stderr_path "#{app_path}/shared/log/unicorn.stderr.log" 

stdout_path "#{app_path}/shared/log/unicorn.stdout.log"

timeout 60

preload_app true
GC.respond_to?(:copy_on_write_friendly=) && GC.copy_on_write_friendly = true

check_client_connection false

run_once = true

before_fork do |server, worker|
  defined?(ActiveRecord::Base) &&
    ActiveRecord::Base.connection.disconnect!

  if run_once
    run_once = false # prevent from firing again
  end

  old_pid = "#{server.config[:pid]}.oldbin"
  if File.exist?(old_pid) && server.pid != old_pid
    begin
      sig = (worker.nr + 1) >= server.worker_processes ? :QUIT : :TTOU
      Process.kill(sig, File.read(old_pid).to_i)
    rescue Errno::ENOENT, Errno::ESRCH => e
      logger.error e
    end
  end
end

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

upstream app_server {
  server unix:/var/www/app_name/shared/tmp/sockets/unicorn.sock;
}

server {
  listen 80;
  server_name xx.xxx.xxx.xxx;
  client_max_body_size 2g;

  root /var/www/app_name/current/public;

# assetsファイル(CSSやJavaScriptのファイルなど)にアクセスが来た際に適用される設定
  location ^~ /assets/ {
    gzip_static on;
    expires max;
    add_header Cache-Control public;
    root /var/www/app_name/current/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://app_server;
  }

  error_page 500 502 503 504 /500.html;
}