0009. Counts only, from the status endpoints

• Status: accepted
• Date: 2026-10-21

Context

The pack needs the player count and a few facts about the server (slots, version, OneSync). The game server serves them as JSON on the game port: dynamic.json has the number of connected clients and the slots, info.json the version string and the server variables, and players.json one entry per player, which holds names and identifiers when the request carries the players token. Whatever reaches Prometheus is kept for weeks and shown on dashboards that people share, so data about single players must never get there, also not by a mistake in a later change.

Considered options

1. Read the count from dynamic.json clients with json_exporter; never request players.json.
2. Count the entries of players.json (json_exporter cannot count array entries, so this needs a small exporter of its own).
3. A resource inside the game server that exports metrics itself.

Decision

Chosen option 1, because dynamic.json already has the count and needs no per-player data at all, and json_exporter is a maintained exporter that runs outside the server process. Option 2 would fetch player data only to throw it away, and option 3 would run code inside the server that it is supposed to watch. The rule is enforced, not only documented: scripts/check_pack.py fails when any scrape config or exporter module names players.json or adds a label such as name, player, identifier, license, ip, endpoint, ping or id, and scripts/smoke_exporters.py checks in CI that the fake server never receives a players.json request and that no such label arrives in Prometheus. The modules read four fields and nothing else (metrics reference).

Consequences

• Good: no player data can reach Prometheus through this pack, and a change that would add some fails CI.
• Good: one series for the count instead of one per player keeps the cardinality budget small.
• Bad: if dynamic.json is ever unavailable while players.json works, there is no player count; the up series of the job shows it.