[krajorama]

TL;DR; better late than never (tm). Turns out we never documented the 1.0.0 text format, even though it's been there since 3.0.0 and selectable in negotiated formats. Direct link to preview: https://deploy-preview-3183--prometheus-docs.netlify.app/docs/instrumenting/exposition_formats/

Summary

Prometheus has requested text/plain;version=1.0.0 (the PrometheusText1.0.0 scrape protocol) since 3.0, and prometheus/common now negotiates, encodes and decodes it, but the exposition formats page only described version 0.0.4.

• Add a Versions section to the Prometheus text format page:
  • 0.0.4: the original version, legacy names only. A missing version is treated as 0.0.4.
  • 1.0.0: the same format with quoted UTF-8 metric and label names, plus the escaping parameter. Links to the escaping schemes and content negotiation pages.
• Say when targets should respond with 1.0.0, and that they must otherwise escape names with the requested scheme.
• Note that Prometheus's text parser ignores the version parameter, so it also ingests quoted UTF-8 names sent as 0.0.4. That is not part of the 0.0.4 format and other consumers may reject it.
• Update the Basic info table: "Supported in", "HTTP Content-Type" and "Supported advanced features" now cover both versions.
• Replace "a missing version falls back to the most recent text format version" with "is treated as 0.0.4", since "most recent" is now ambiguous and prometheus/common treats a missing version as 0.0.4.

Context

• Relates to Clarify accepted content types in the docs prometheus#15830, where users report they cannot find any documentation of PrometheusText1.0.0.
• Raised again in expfmt: support Prometheus text format 1.0.0 common#1035 ("There's a Prometheus 1.0.0 text format? I don't see it documented").
• Version/behavior claims checked against config/config.go, scrape/scrape.go and model/textparse at v0.300.0 and main of prometheus/prometheus, and expfmt in prometheus/common main.

Test plan

• In-page anchor and cross-file links point to existing headings and files.
• Rendered page not checked locally (table cells use the same inline HTML pattern as before); please check the preview.