prometheus / prometheus/docs

exposition format: How to deal with duplicate metric families

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exposition format
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Description

The current spec is crystal clear that duplicate metric families (and, correspondingly, multiple TYPE and HELP lines for the same metric name in the text format) are not allowed in a single exposition.

However, the federation endopint of the prometheus server is currently in breach of that, see. https://github.com/prometheus/prometheus/issues/1963 .

This issue is about whether we should allow duplicate metric families, and if yes, how to deal with them.
(Problematic right now is that the Prometheus server tolerates them if ingesting protobuf, and just ingests them one after another, while it rejects any text format exposition with multiple TYPE or HELP lines for the same metric name.)

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reading the exposition-format specification and the linked Prometheus issue about federation output. The issue names no files or tests; determine whether duplicate metric families should be permitted and, if so, document the intended handling and update the relevant specification.

Written by the indexing model from the issue text.

Assessment

Domain
documentation
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
20/100

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