federation endpoint should include HELP/TYPE metadata

[fche]

What did you do?

Started consuming /federate?match[]= data by other tools, as though it were a normal prometheus-exporter format.

What did you expect to see?

HELP and TYPE metadata passed through from the upstream exporters.

What did you see instead? Under which circumstances?

Always
# TYPE .... untyped

This makes the federation facility lossy in terms of information, especially with respect to summary/histogram types.

This was with prometheus 2.0.0

[brian-brazil]

This is as expected, and has always worked this way.

It makes more sense to ask questions like this on the prometheus-users mailing list rather than in a GitHub issue. On the mailing list, more people are available to potentially respond to your question, and the whole community can benefit from the answers provided.

[fche]

Sorry - it did not seem like a "how to use" question but a problem. I understand it's always worked this way. Is the opinion that this is good and should stay that way?

[brian-brazil]

That is a complicated question. This is not what federation is for in any case, if you need this use the text format parser directly on the targets.

[fche]

Federation could be useful if it federates (centralizes/abstracts) the targets. Often one does not even have access to the individual targets (because they're on an isolated network vlan as in kubernetes). To what extent would a higher-tier prometheus server be able to do all the same calculations on a federated data stream (sans metadata) as it could if it did reach the targets directly?

[brian-brazil]

https://www.robustperception.io/federation-what-is-it-good-for/

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.