Question

How to fix 502 Bad Gateway error message?

Posted December 31, 2020 205 views
NginxDigitalOceanPythonBig DataDigitalOcean Droplets

I was trying to upload a data file of around 600 MB in my project which is hosted in digital ocean. It tries to upload but 502 Bad Gateway Nginx error is shown.

While the upload completely works fine on my local system.

When I tried:

sudo tail -30 /var/log/nginx/error.log

It shows:

[error] 132235#132235: *239 upstream prematurely closed connection while reading response header from upstream, client: client's ip, server: ip, request: "POST /submit/ HTTP/1.1", upstream: "http://unix:/run/gunicorn.sock:/submit/", host: "ip", referrer: "http://ip"

After,

sudo nano /etc/nginx/sites-available/myproject

the nginx code

server {
    listen 80;
    server_name ip;
    client_max_body_size 999M;

    location = /favicon.ico { access_log off; log_not_found off; }
    location /static/ {
       alias  /root/static/;
    }
    location / {
        include proxy_params;
        proxy_pass http://unix:/run/gunicorn.sock;
    }
}

How to fix this?

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2 answers

Hi there @rikeshk012330,

It looks like that your Gunicorn service has crashed and Nginx is unable to connect to it.

To fix the error you have to start the Gunicorn service.

For more information on how to troubleshoot 502 Nginx errors, I could suggest following the steps from this answer here:

https://www.digitalocean.com/community/questions/502-bad-gateway-nginx-2

Regards,
Bobby

  • The next article didn’t answer my question. Gunicorn gets crashed when trying to convert large files which takes more than 10 minutes and again the server runs itself when I go back to the homepage. Files about 100MB and small files are also processed but with the large files, there exists a issue it takes some time to process. So, this thing works completely file on local server. Please explain more details about this and to solve this.

    • Hello,

      It sounds like that Gunicorn might be crashing, have you Gunicorn error log for more information?

      I could also suggest checking your syslog to see if the service is being killed due to out of memory. If this is the case you could try adding some extra RAM or/and a SWAP file.

      Regards,
      Bobby

Gunicorn is working. My memory logs are:


root@develop-110:~# free -m
              total        used        free      shared  buff/cache   available
Mem:           3936         354        2308          12        1272        3283
Swap:             0           0           0

Only with large file uploads, I have 502 gateway errors

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