Question

502 Bad Gateway (nginx/1.18.0 (Ubuntu)) with Django App

Hi DigitalOcean Team and Developers!

I’m currently hosting my Django App in DigitalOcean, i encountered an issue in the process, it’s related to a 502 Bad Gateway error i receive while trying to access my app. I’m actually deploying a Python/Django app with Nginx, Gunicorn and a MySQL database. I followed the tutorial word to word and saw there was a lot of users fighting this issue, i don’t know if there is something missing in the tutorial or if i missed something.

These are the error logs i’m receiving, status and my configurations from both NGINX and Gunicorn

NGINX Configurations: i was listening to port 80 in both server blocks which lead to a bad request 400 error response, once removed the 502 bad gateway error kicked in

server {

      server_name domain.com www.domain.com;

      location /favicon.ico {access_log off; log_not_found off;}

      location / {
         include proxy_params;
         proxy_pass https://unix:/home/lrodri04/project/project/project.sock;
     }


    listen [::]:443 ssl ipv6only=on; # managed by Certbot
    listen 443 ssl; # managed by Certbot
    ssl_certificate /etc/letsencrypt/live/domain.com/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/domain.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 {
    if ($host = www.domain.com) {
        return 301 https://$host$request_uri;
    } # managed by Certbot

    if ($host = domain.com) {
        return 301 https://$host$request_uri;
    } # managed by Certbot

    listen 80;

    listen [::]:80;

    server_name domain.com www.domain.com;
    return 404; # managed by Certbot
}

NGINX Status:

Command:
sudo nginx -t

Output:
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful

NGINX Error Logs:

Command:
sudo tail -f /var/log/nginx/error.log


Output:
2021/09/07 02:02:00 [error] 145950#145950: *1 peer closed connection in SSL handshake while SSL handshaking to upstream, client: 138.94.121.91, server: domain.com, request: "GET / HTTP/1.1", upstream: "https://unix:/home/lrodri04/project/project/project.sock:/", host: "www.domain.com"
2021/09/07 02:05:43 [error] 145950#145950: *5 peer closed connection in SSL handshake while SSL handshaking to upstream, client: 138.94.121.91, server: domain.com, request: "GET / HTTP/1.1", upstream: "https://unix:/home/lrodri04/project/project/project.sock:/", host: "www.domain.com"
2021/09/07 02:10:29 [error] 145950#145950: *8 peer closed connection in SSL handshake while SSL handshaking to upstream, client: 138.94.121.91, server: domain.com, request: "GET / HTTP/1.1", upstream: "https://unix:/home/lrodri04/project/project/rpoject.sock:/", host: "www.domain.com"
2021/09/07 02:14:02 [error] 146423#146423: *2 peer closed connection in SSL handshake while SSL handshaking to upstream, client: 138.94.121.91, server: domain.com, request: "GET / HTTP/1.1", upstream: "https://unix:/home/lrodri04/project/project/project.sock:/", host: "www.domain.com"
2021/09/07 02:18:05 [error] 146571#146571: *2 peer closed connection in SSL handshake while SSL handshaking to upstream, client: 138.94.121.91, server: domain.com, request: "GET / HTTP/1.1", upstream: "https://unix:/home/lrodri04/project/project/project.sock:/", host: "www.domain.com"
2021/09/07 02:19:31 [error] 146571#146571: *2 peer closed connection in SSL handshake while SSL handshaking to upstream, client: 138.94.121.91, server: domain.com, request: "GET / HTTP/1.1", upstream: "https://unix:/home/lrodri04/project/project/project.sock:/", host: "www.domain.com"
2021/09/07 02:23:37 [alert] 146889#146889: *2 open socket #14 left in connection 7
2021/09/07 02:23:37 [alert] 146889#146889: aborting
2021/09/07 02:24:19 [error] 146954#146954: *2 peer closed connection in SSL handshake while SSL handshaking to upstream, client: 138.94.121.91, server: domain.com, request: "GET / HTTP/1.1", upstream: "https://unix:/home/lrodri04/project/project/project.sock:/", host: "www.domain.com"
2021/09/07 02:28:39 [error] 147104#147104: *2 peer closed connection in SSL handshake while SSL handshaking to upstream, client: 138.94.121.91, server: domain.com, request: "GET / HTTP/1.1", upstream: "https://unix:/home/lrodri04/project/project/project.sock:/", host: "www.domain.com"

NGINX Status:

Command:
sudo systemctl status nginx

● nginx.service - A high performance web server and a reverse proxy server
     Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
     Active: active (running) since Tue 2021-09-07 02:27:53 UTC; 16min ago
       Docs: man:nginx(8)
    Process: 147090 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process on; (code=exited, status=0/SUCCESS)
    Process: 147102 ExecStart=/usr/sbin/nginx -g daemon on; master_process on; (code=exited, status=0/SUCCESS)
   Main PID: 147103 (nginx)
      Tasks: 2 (limit: 1136)
     Memory: 6.8M
     CGroup: /system.slice/nginx.service
             ├─147103 nginx: master process /usr/sbin/nginx -g daemon on; master_process on;
             └─147104 nginx: worker process

Sep 07 02:27:53 Sealena systemd[1]: Starting A high performance web server and a reverse proxy server...
Sep 07 02:27:53 Sealena systemd[1]: Started A high performance web server and a reverse proxy server.

Gunicorn Configurations:

[Unit]
Description=gunicorn daemon
After=network.target

[Service]
User=lrodri04
Group=www-data
WorkingDirectory=/home/lrodri04/project/project
ExecStart=/home/lrodri04/environments/project/bin/gunicorn --access-logfile - --workers 3 --bind unix:/home/lrodri04/project/project/project.sock project.wsgi:application

[Install]
WantedBy=multi-user.target

Gunicorn Status:

● gunicorn.service - gunicorn daemon
     Loaded: loaded (/etc/systemd/system/gunicorn.service; enabled; vendor preset: enabled)
     Active: active (running) since Tue 2021-09-07 02:05:08 UTC; 50min ago
   Main PID: 146128 (gunicorn)
      Tasks: 4 (limit: 1136)
     Memory: 221.2M
     CGroup: /system.slice/gunicorn.service
             ├─146128 /home/lrodri04/environments/Sealena/bin/python3 /home/lrodri04/environments/Sealena/bin/gunicorn --access-logfile - --workers 3 --bind unix:/home/lrodri04/Sealena/Sealena/Sealen>
             ├─146458 /home/lrodri04/environments/Sealena/bin/python3 /home/lrodri04/environments/Sealena/bin/gunicorn --access-logfile - --workers 3 --bind unix:/home/lrodri04/Sealena/Sealena/Sealen>
             ├─146977 /home/lrodri04/environments/Sealena/bin/python3 /home/lrodri04/environments/Sealena/bin/gunicorn --access-logfile - --workers 3 --bind unix:/home/lrodri04/Sealena/Sealena/Sealen>
             └─147133 /home/lrodri04/environments/Sealena/bin/python3 /home/lrodri04/environments/Sealena/bin/gunicorn --access-logfile - --workers 3 --bind unix:/home/lrodri04/Sealena/Sealena/Sealen>

Sep 07 02:19:31 Sealena gunicorn[146606]: [2021-09-07 02:19:31 +0000] [146606] [INFO] Worker exiting (pid: 146606)
Sep 07 02:19:31 Sealena gunicorn[146780]: [2021-09-07 02:19:31 +0000] [146780] [INFO] Booting worker with pid: 146780
Sep 07 02:22:55 Sealena gunicorn[146458]:  - - [07/Sep/2021:02:22:55 +0000] "GET / HTTP/1.0" 400 143 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome>
Sep 07 02:23:28 Sealena gunicorn[146780]:  - - [07/Sep/2021:02:23:28 +0000] "GET / HTTP/1.0" 400 143 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome>
Sep 07 02:24:19 Sealena gunicorn[146128]: [2021-09-07 02:24:19 +0000] [146128] [CRITICAL] WORKER TIMEOUT (pid:146141)
Sep 07 02:24:19 Sealena gunicorn[146141]: [2021-09-07 02:24:19 +0000] [146141] [INFO] Worker exiting (pid: 146141)
Sep 07 02:24:20 Sealena gunicorn[146977]: [2021-09-07 02:24:20 +0000] [146977] [INFO] Booting worker with pid: 146977
Sep 07 02:28:39 Sealena gunicorn[146128]: [2021-09-07 02:28:39 +0000] [146128] [CRITICAL] WORKER TIMEOUT (pid:146780)
Sep 07 02:28:39 Sealena gunicorn[146780]: [2021-09-07 02:28:39 +0000] [146780] [INFO] Worker exiting (pid: 146780)
Sep 07 02:28:40 Sealena gunicorn[147133]: [2021-09-07 02:28:40 +0000] [147133] [INFO] Booting worker with pid: 147133


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Accepted Answer

Hi @Lrodri04,

In 99% of the cases, when using such a setup and you get a 502 Bad Gateway, and your Nginx starts without a problem, you can exclude Nginx as the source of the issue.

Most probably it’s a problem with the configuration or code of the Application. I’ll recommend turning your attention to your Python/Django application and a misconfiguration there.

Additionally, I can take a look at the tutorial you’ve used to deploy your app and try to see if there could be some potential issues somewhere.

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