Error 520, in backend logs empty request and code 000

What is the name of the domain?

sambot.ru

What is the error number?

520

What is the error message?

Web server is returning an unknnown error

What is the issue you’re encountering

nginx can’t get request from what goes from Cloudflare. It gets browser etc, but empty request. And it answers with code 000

What steps have you taken to resolve the issue?

It happens only sometimes. With the same clients. There can be 1000-2000 such reqeusts per day or about 20.
I can’t figure out why the same client makes the same response and usually it’s ok. But sometimes it gets 520 and nginx in the backend sees empty request.

What are the steps to reproduce the issue?

It happens from time to time. The same request from the same client can go tens thousand times per day successfully and suddenly I see empty request.
Clients can be:Android, iPhone, Mac OS X. I see nothing in common.

Error 520 occurs when the origin server returns an empty, unknown, or unexpected response to Cloudflare.

Does disable the http2 to origin fix your issue ?

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