Nginx - Access Http custom headers v2

Question

Similar to this question and this question, I have a client (bazel) that is sending requests to nginx.

The client is adding a custom header called build_id as HTTP_BUILD_ID to each request.

I just want to log this header from nginx.

I wrote a small python flask application and printed all the headers and it showed that HTTP_BUILD_ID is indeed part of the request.

Unfortunately, nginx can't find it. This is what my log_format looks like with the addition of $http_build_id.

log_format main '$remote_addr - $upstream_cache_status [$time_local]
                '"$request" $status $body_bytes_sent '
                '[$http_build_id]'
                '"$http_referer" "$http_user_agent"';

Raul · Accepted Answer · 2019-10-11 17:38:38Z

1

If you are sending it as HTTP_BUILD_ID, then you should use "$http_http_build_id" in your log_format

Also, do check your virtual host (server) definition to make sure it's using the main format. Some default installs look like: access_log FILE combined, where combined is a predefined format. Read more about that here

As pointed by the OP, installing the nginx-echo-headers package pointed out to some invalid headers. Adding underscores_in_headers on; fixed the issue.

edited Oct 11, 2019 at 17:38

answered Oct 11, 2019 at 5:01

Raul

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4 Comments

GGhe Over a year ago

The header HTTP_USER_AGENT is shown as $http_user_agent. While HTTP_REFERER is seen as $http_referer. I assumed that HTTP_BUILD_ID would be seen as $http_build_id.

Raul Over a year ago

Look at x-forwarded-for. To log it, it's http_x_forwarded_for. User-Agent, Referrer, these are not prefixed by HTTP when sent by the browser. In nginx, to get a header, you do http_HEADER. And in your case, because your header is HTTP_BUILD_ID, you have the double http

GGhe Over a year ago

Your answer is semi correct. I used $http_build_id but I needed to fix some configuration. Please update your answer. I used github.com/brndnmtthws/nginx-echo-headers to echo out what my requests were and then realized that it was saying that my header was invalid. I then added underscores_in_headers on; to fix the issue.

Raul Over a year ago

@GGhe, thanks, updated. I will do a re-test on my end with that. Thanks for digging in more about this!

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