prometheus / prometheus/exporter-toolkit

Automatically enable `--web.systemd-socket` when `$LISTEN_FDS` is set

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Dominant language
Go
Stars
311
Forks
109
Avg merge
3d 59m
Merged PRs (30d)
6

Description

Almost two years ago (#95) exporter-toolkit added the --web.systemd-socket flag to listen on a pre-opened socket passed as a file descriptor. We have used this feature with success since then. However, having to manually set the flag when using a socket is quite cumbersome and error prone. Additionally, when the flag is set, exporters fail to start unless a socket is passed. This is a reasonable behavior as one explicitly told the exporter to use an existing socket.

However, it would be better to check the $LISTEN_FDS environment variable and automatically use a socket if that variable is set. If that variable is not set, the exporter would fall back to opening a port on its own.

Contributor guide

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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

Locate the existing --web.systemd-socket handling and the exporter startup path, then inspect how $LISTEN_FDS is currently treated. Done means a set $LISTEN_FDS value selects the pre-opened socket automatically, while its absence preserves normal port opening, with coverage for both cases.

Written by the indexing model from the issue text.

Assessment

Tech stack
go
Domain
observability-sre
Issue type
Feature
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
48/100

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