Termination marker for scrapes

[brian-brazil]

prometheus/docs#546

[brian-brazil]

I'm for # END\n at the end of the format (maybe not the \n if there's an EOF, that's a common mistake).

[RichiH]

# END\n makes sense. Short IETF speak suggestion: MUST be sent, MUST be accepted without it being sent, SHOULD be exposed to the user.if missing.

[brian-brazil]

MUST be accepted without it being sent,

The whole point of this is to prevent incomplete scrapes, it MUST be rejected if it isn't sent.

[RichiH]

Isn't partial information better than no information at all?

I don't feel strongly either way, as things not being up (or whatever other implementations call it) is a strong incentive to dig at what's wrong.

[brian-brazil]

Isn't partial information better than no information at all?

It's worse than no information, as queries tend to be written presuming that a whole scrape comes at once.

Correctly dealing with a model where an arbitrary subset of the data can be returned at each scrape would be close to impossible, even for an expert.

[RichiH]

Specific to text format (and maybe some others).