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I have created a web application with Django Channels which I face problems with while trying to set up with Supervisor system.

To start with, the application locally works well.

Remotely (I use an AWS EC2 instance with Ubuntu Server 18.04 LTS), when run with a command daphne -b 0.0.0.0 -p 8000 mysite.asgi:application it also works well.

However, I cannot make it work with Supervisor. I follow instructions from the official Django Channels docs (https://channels.readthedocs.io/en/latest/deploying.html) and therefore I have:

• 
  

  nginx config file:

  
  
  

  upstream channels-backend 
   server localhost:8000;
  
  
  server 
   server_name www.example.com;
  
   keepalive_timeout 5;
   client_max_body_size 1m;
  
   access_log /home/ubuntu/django_app/logs/nginx-access.log;
   error_log /home/ubuntu/django_app/logs/nginx-error.log;
  
   location /static/ 
   alias /home/ubuntu/django_app/mysite/staticfiles/;
   
  
   location / 
   try_files $uri @proxy_to_app;
   
  
   location @proxy_to_app 
   proxy_pass http://channels-backend;
  
   proxy_http_version 1.1;
   proxy_set_header Upgrade $http_upgrade;
   proxy_set_header Connection "upgrade";
  
   proxy_redirect off;
   proxy_set_header Host $host;
   proxy_set_header X-Real-IP $remote_addr;
   proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
   proxy_set_header X-Forwarded-Host $server_name;
   
  
   listen 443 ssl; # managed by Certbot
   ssl_certificate /etc/letsencrypt/live/www.example.com/fullchain.pem; # managed by Certbot
   ssl_certificate_key /etc/letsencrypt/live/www.example.com/privkey.pem; # managed by Certbot
   include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
   ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
  
  
  server 
   listen 80;
   server_name www.example.com;
  
   if ($host = www.example.com) 
   return 301 https://$host$request_uri;
   # managed by Certbot
  
   return 404; # managed by Certbot
  
  

  
  


• 
  

  Supervisor config file:

  
  
  

  [fcgi-program:asgi]
  
  socket=tcp://localhost:8000
  
  directory=/home/ubuntu/django_app/mysite
  
  command=/home/ubuntu/django_app/venv/bin/daphne -u /run/daphne/daphne%(process_num)d.sock --fd 0 --access-log - --proxy-headers mysite.asgi:application
  
  numprocs=4
  
  process_name=asgi%(process_num)d
  
  autostart=true
  autorestart=true
  
  stdout_logfile=/home/ubuntu/django_app/logs/supervisor_log.log
  redirect_stderr=true
  

  
  

When set this way, the webpage does not work (504 Gateway Time-out). In the Supervisor log file I see:

2018-11-14 14:48:21,511 INFO Starting server at fd:fileno=0, unix:/run/daphne/daphne0.sock
2018-11-14 14:48:21,516 INFO HTTP/2 support enabled
2018-11-14 14:48:21,517 INFO Configuring endpoint fd:fileno=0
2018-11-14 14:48:22,015 INFO Listening on TCP address 127.0.0.1:8000
2018-11-14 14:48:22,025 INFO Configuring endpoint unix:/run/daphne/daphne0.sock
2018-11-14 14:48:22,026 CRITICAL Listen failure: [Errno 2] No such file or directory: '1416' -> b'/run/daphne/daphne0.sock.lock'
2018-11-14 14:48:22,091 INFO Starting server at fd:fileno=0, unix:/run/daphne/daphne2.sock
2018-11-14 14:48:22,096 INFO HTTP/2 support enabled
2018-11-14 14:48:22,097 INFO Configuring endpoint fd:fileno=0
2018-11-14 14:48:22,135 INFO Starting server at fd:fileno=0, unix:/run/daphne/daphne3.sock
2018-11-14 14:48:22,152 INFO HTTP/2 support enabled
2018-11-14 14:48:22,153 INFO Configuring endpoint fd:fileno=0
2018-11-14 14:48:22,237 INFO Listening on TCP address 127.0.0.1:8000
2018-11-14 14:48:22,241 INFO Listening on TCP address 127.0.0.1:8000
2018-11-14 14:48:22,242 INFO Configuring endpoint unix:/run/daphne/daphne3.sock
2018-11-14 14:48:22,242 CRITICAL Listen failure: [Errno 2] No such file or directory: '1419' -> b'/run/daphne/daphne3.sock.lock'
2018-11-14 14:48:22,252 INFO Configuring endpoint unix:/run/daphne/daphne2.sock
2018-11-14 14:48:22,252 CRITICAL Listen failure: [Errno 2] No such file or directory: '1420' -> b'/run/daphne/daphne2.sock.lock'

etc.

Please note that in the Supervisor command the Daphne process is invoked in another way (with other set of parameters) than I run it before - instead of parameters for address and port, there are parameters for socket and file descriptor (about which I do not know much at all). I suspect that it is the reason of the encountered error.

Any help or suggestions will be highly appreciated.

The relevant packages versions:

channels==2.1.2
channels-redis==2.2.1
daphne==2.2.1
Django==2.1.2

EDIT:

When I create empty files for socket files (which are present in command for Daphne in the Supervisor config file), ie. /run/daphne/daphne0.sock, /run/daphne/daphne1.sock, etc., then the log file states the following:

2018-11-15 10:24:38,289 INFO Starting server at fd:fileno=0, unix:/run/daphne/daphne0.sock
2018-11-15 10:24:38,290 INFO HTTP/2 support enabled
2018-11-15 10:24:38,280 INFO Configuring endpoint fd:fileno=0
2018-11-15 10:24:38,458 INFO Listening on TCP address 127.0.0.1:8000
2018-11-15 10:24:38,475 INFO Configuring endpoint unix:/run/daphne/daphne0.sock
2018-11-15 10:24:38,476 CRITICAL Listen failure: Couldn't listen on any:b'/run/daphne/daphne0.sock': [Errno 98] Address already in use.

Question: should these files not be empty? What should they include?

In the supervisor ASGI config file, in the following line

command=/home/ubuntu/django_app/venv/bin/daphne -u /run/daphne/daphne%(process_num)d.sock --fd 0 --access-log - --proxy-headers mysite.asgi:application

replace --fd 0 with --endpoint fd:fileno=0.

Issue: https://github.com/django/daphne/issues/234

Fabio's answer, with replacing the file descriptor parameter for the endpoint parameter, presents a quick workaround for this problem (which appeared to be a bug in the Daphne code).

However, the fix in Daphne repository was quickly committed so that the original instructions work well.

As a side note (for people still getting critical listen failures which I wrote about in the original question), please be sure that the physical location for socket files (/run/daphne/ in my case) is accessible - I spent too much time just to discover that simply creating the daphne folder in /run catalog does the job (even though I run everything with sudo)... For precautionary measures one may consider redirecting the socket files to another folder, e.g. /tmp which does let creating a directory without sudo permission.