Randomly occuring 502 Bad Gateway errors

I keep getting Bad Gateway errors when uploading large files on cloudflare, the error received is the black and white page that just says “502 Bad Gateway” and “cloudflare” which according to https://developers.cloudflare.com/support/troubleshooting/cloudflare-errors/troubleshooting-cloudflare-5xx-errors indicates this is an issue on cloudflares end and not on the origin server.

What I am trying to do is upload files to a web application, the frontend uses Plupload (javascript) to split large files into chunks of 100mb, and then uploads the chunks 1 by 1 to the backend of the application. This application runs behind a reverse proxy using nginx.

When uploading a large file, usually the first few chunks upload succesfully, but at random times uploading one chunk gives the above 502 error.

Both the logs of nginx and the application show no trace of the failing chunk upload request.

We would definitely like to investigate further and sorry that you have been dealing with that.

I have opened a ticket for you, 3045896, and will be sending a message to you from it, so we can get some further information.


Hi @raeven05 ,

I have responded on the ticket with some findings.

Let’s take this up on the ticket to troubleshoot further.

Thank you.

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