client sent header field with too long length value while processing HTTP/2 connection

[Sergey Kandaurov]

> On 24 Jan 2020, at 21:02, andreios <nginx-forum at forum.nginx.org> wrote:
> 
> "client sent header field with too long length value while processing HTTP/2
> connection"

This means that a header field name or value was detected as if it
was represented as a string literal with length encoded as an integer
using of more than 4 bytes (allows to represent values above 2097278).
Although the integer representation used by HPACK allows for values
of indefinite size, this is not supported by nginx.

See RFC 7541, section 5.2 for some details.

You could try to see what's actually gets sent, for debugging purpose
(you might want to decrypt it first).

-- 
Sergey Kandaurov