feature request: Allow user-supplied request_id as HTTP header

[stevenscg]

The request_id added with #1650 is great for tracing vault requests and responses.

It would be a great to be able to trace a request among and across services including vault (and consul and nomad - hopefully).

With my internal services, I have some HTTP middleware that checks for the HTTP header X-Request-ID (the specific header is actually configurable) on each incoming request.

If the header is found and meets some arbitrary length constraints, each service uses the provided value as the request_id internally. This value is written to the request and system logs and we use it to lookup a complete request chain in our centralized logging systems.

If the header is not found on the request, a UUID is generated just like vault does today.

At least for my own services, this was a very simple but very powerful way to support distributed tracing and help in debugging issues.

I can't think of any security issues with a feature like this, but if there were concerns, it might be reasonable to allow a vault administrator to specify the name of the HTTP header as part of their listener configuration to enable this feature.

[jefferai]

You can already do this; in 0.6.5 you can set a list of headers that you want to appear in audit logs, including whether you want those values HMAC'd or not.

[stevenscg]

Works for me! Thanks Jeff.

Found it in the changelog and #2321. Excellent!