Request headers size limit

[Javier Vazquez]

Hello,

I'm trying to hit an endpoint with a very long url (query parameters can accept thousands of ids). After some investigation, I see in Envoy's code a hard limit set to 60K (https://github.com/envoyproxy/envoy/blob/f3b110091c0a0e1ae3abd4ce245d57296e1e868d/source/common/http/conn_manager_impl.cc#L543).  

This is inline with my tests, if I go beyond 60Kb I get back a HTTP 431.

 

Are there any plans to make this configurable or is a hard limit based on the libraries used Envoy?

Thanks,

Javier Vazquez

[Matt Klein]

HTTP/1.1 has a hard limit imposed by http_parser which might be configurable with a compile define (not sure) but would definitely require an Envoy recompile. HTTP/2 we could easily make configurable. I would open an issue to track.

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Matt Klein

Software Engineer

mkl...@lyft.com

https://calendly.com/mattklein123

[Javier Vazquez]

Matt, thanks for the info.

Sorry for this n00b question but I haven't coded C++ in a very long time. I tried a quick test to increase HTTP/1.1 limit by overriding the max value with a define macro but it didn't pickup the change.

Steps:

1) Override http_parser library max header size by adding "#define HTTP_MAX_HEADER_SIZE (128*1024)" @ https://github.com/envoyproxy/envoy/blob/f3b110091c0a0e1ae3abd4ce245d57296e1e868d/source/common/http/http1/codec_impl.h#L2

2) Bump EnvoyProxy's limit to 100KB @ https://github.com/envoyproxy/envoy/blob/f3b110091c0a0e1ae3abd4ce245d57296e1e868d/source/common/http/conn_manager_impl.cc#L550

3) Recompile

Result:

EnvoyProxy's limit is 80KB (http_parser library default), not the 100KB limit expected.  

Additional Info:

http_parser.h -> https://github.com/nodejs/http-parser/blob/77310eeb839c4251c07184a5db8885a572a08352/http_parser.h#L63

Any ideas?

Thanks,

Javier

[Matt Klein]

That define change won't change the value when http_parser itself is compiled. Try the following:

1) Fork http_parser

2) Change the value

3) Repoint Envoy build to your fork: https://github.com/envoyproxy/envoy/blob/master/bazel/repository_locations.bzl#L75

4) Recompile

And that should work.

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[Javier Vazquez]

Thanks, it worked like a charm!