host not found in upstream "app" nginx not serving the app stuck on welcome page

Question

Its my first time setting up nginx and unicorn.

My capistrano deployment went through and everything succeeded.

here is my unicorn.rb

#app_dir = File.expand_path('../../', __FILE__)
#shared_dir = File.expand_path('../../../shared/', __FILE__)

preload_app true 
worker_processes 4
timeout 30
working_directory "home/deploy/appname"
shared_dir = "home/deploy/appname/shared"

# Set up socket location 
# by default unicorn listens on 8080
listen "#{shared_dir}/tmp/sockets/unicorn.sock", :backlog => 64

# Logging
stderr_path "#{shared_dir}/log/unicorn.stderr.log"
stdout_path "#{shared_dir}/log/unicorn.stdout.log"

# Set master PID location
pid "#{shared_dir}/tmp/pids/unicorn.pid"

#must set preload app true to use before/after fork
before_fork do |server, worker|
  defined?(ActiveRecord::Base) and ActiveRecord::Base.connection.disconnect!
  
  #before forking, this is suppose to kill the master process that belongs to the oldbin
  #enables 0 downtime to deploy

  old_pid = "#{shared_dir}/tmp/pids/unicorn.pid.oldbin"
  if File.exists?(old_pid) && server.pid != old_pid
    begin
      Process.kill("QUIT", File.read(old_pid).to_i)
    rescue Errno::ENOENT, Errno::ESRCH
    end
  end
end

after_fork do |server, worker|
  defined?(ActiveRecord::Base) and ActiveRecord::Base.establish_connection
end

# before_exec do |server|
#   ENV['BUNDLE_GEMFILE'] = "#{app_dir}/Gemfile"
# end

my nginx conf at /etc/nginx/nginx.conf

user www-data;
worker_processes 4;
pid /run/nginx.pid;

events {
        worker_connections 768;
        # multi_accept on;
}


http {  
       sendfile on;
       tcp_nopush on;
       tcp_nodelay on;
       keepalive_timeout 65;
       types_hash_max_size 2048;
       
 
       include /etc/nginx/mime.types;
       default_type application/octet-stream;

       access_log /var/log/nginx/access.log;
       error_log /var/log/nginx/error.log;


       gzip on;
       gzip_disable "msie6";

       include /etc/nginx/conf.d/*.conf;
       include /etc/nginx/sites-enabled/*;
} 

my default file at /etc/nginx/sites-enabled/default

upstream app_server {
  #path to unicorn sock file, as defined previously
  server unix:/home/deploy/appname/shared/tmp/sockets/unicorn.sock fail_timeout=0;
}

    server {
        listen 80;
    
        root /home/deploy/appname;
    
     try_files $uri/index.html $uri @app;
    
        #click tracking
        access_log /var/log/nginx/appname_access.log combined;
    
        error_log /var/log/nginx/appname_error.log;
    
        location @app {
          proxy_set_header X-Forwarded-For $remote_addr;
          proxy_set_header Host $http_host;
          proxy_redirect off;
          proxy_pass http://app;
        }
    
        error_page 500 502 503 504 /500.html;
        client_max_body_size 4G;
        keepalive_timeout 10;
    }

when I do this

deploy@localhost:~$ sudo nginx -s reload
nginx: [emerg] host not found in upstream "app" in /etc/nginx/sites-enabled/default:46

When I head into

/shared/tmp/sockets

I don't have a file in there. I don't think I should create it manually. I am using capistrano 3. Am I suppose to generate this file?

I am using

require 'capistrano3/unicorn' #in capfile

in deploy.rb

symbolic files and directories

set :linked_files, %w{config/database.yml config/secrets.yml}
set :linked_dirs, %w{tmp/pids tmp/cache tmp/sockets log bin vendor/bundle public/system}

#just pointing to our unicorn.rb
set :unicorn_config_path, "config/unicorn.rb"

#capistrano tasks and processes

after "deploy", "deploy:cleanup"

namespace :deploy do

  desc 'Restart application'
  task :restart do
    on roles(:app), in: :sequence, wait: 5 do
      invoke 'unicorn:restart'
    end
  end

  after :finishing, "deploy:cleanup"

end

I put my cap file here because I notice no log on unicorn restart in my cap production deploy log. I am not sure if this helps.

I made sure the working_directory matches the root in the default nginx page. I made sure the listen in unicorn matches the upstream app server unix in the default page. I made sure the nginx.conf file included the default config nginx page in sites-enabled.

Answer 1

Well this is 6 months old, but I'm going to answer it anyways. The issue is proxy_pass in @app in sites_enabled/default. It's trying to pass to the upstream server http://app , but you don't have that upstream set, you have it named app_server.

You need to rename: proxy_pass http://app

to: proxy_pass http://app_server