CFP: Expose URL Path in HTTP metrics

[zhilingc]

Cilium Feature Proposal

Thanks for taking time to make a feature request for Cilium! If you have usage questions, please try the slack channel and see the FAQ first.

Is your feature request related to a problem?

Hubble L7 metrics currently does not export the http URL path, even though its available in Hubble flows; Not having access to this information is a huge bummer and a large part of why we want L7 visibility in the first place.

The only way to access this information outside of hubble currently is to export the file using --hubble-export-file-path and then parse that information, which isn't ideal...

Describe the feature you'd like

Expose the URL path as labels for the hubble http metrics http_requests_total, http_responses_total and http_request_duration_seconds.

(Optional) Describe your proposed solution

I'm happy to give this a shot if acceptable :)

[Joffref]

Take my contribution with caution, I'm new to Cilium

As far as I understand it L7 observability with Hubble monitor each HTTP request sent to your services, meaning that cardinality of such a thing might be infinite.

I'm letting you check out this comment: prometheus/client_golang#491 (comment)

[rolinh]

Thanks for the CFP @zhilingc. @Joffref is absolutely right: the cardinality of the metrics could literally explose which means we unfortunately cannot expose URL path in HTTP metrics.

[zhilingc]

@rolinh @Joffref That's regrettable, since it nerfs the out of the box metrics significantly for a large swath of applications, but i see where the decision is coming from. Thanks for the replies :)

[dbazhal]

This feature is available in istio service mesh, it uses same envoy as cilium does, and it does not contain such metrics out of the box too. So one nice solution would be to let user decide turning these dimensions on.
Could we /reopen?

[Joffref]

I understand such metric, in case of a low cardinality in url path, but I'm not sure about implementing this directly inside cilium. Is there any workaround we can think about to enable this dimension without modifying the code base ?

[michi-covalent]

ok reopen and have some more discussion 🚀

[chancez]

I think if we can consider supporting this, but it would need to support a few things to keep cardinality reasonable:

• Needs to be opt in.
• The URLs should be "allow listed" with a regex to match, and then remove any parameters from the URL and replace them with placeholders.

Example:
URLs might be:

/user/chance/details
/user/michi/details

And the config/regex would need to support transforming the URL into /user/USERNAME/details within the metrics labels.

[github-actions]

This issue has been automatically marked as stale because it has not
had recent activity. It will be closed if no further activity occurs.

[github-actions]

This issue has not seen any activity since it was marked stale.
Closing.

[dbazhal]

/reopen