feat(metrics): fixed-cardinality active_users gauge + restored dashboard panel - #180
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…ard panel
Brings back "Active users (last 1 h)" without the per-user series that
blew the Grafana free tier: the middleware stamps user-id -> last-seen
in memory and _ActiveUsersCollector emits active_users{window="1h"|"24h"}
at scrape time - 2 series total regardless of user count, and no user
identifiers ever become metric labels.
Trade-offs vs the removed user_page_views_total: count resets on deploy
(in-memory) and there is no per-user breakdown.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Summary
Restores the "Active users (last 1 h)" dashboard panel removed in #179 — at a cost of 2 series instead of the 12,905 the old
user_page_views_totalapproach consumed.user_id → last-seenin process memory on authenticated GETs; user identifiers never become metric labels (privacy bonus)._ActiveUsersCollectoremitsactive_users{window="1h"}/{window="24h"}gauges at scrape time — cardinality fixed regardless of user count.frontend.jsonpanel restored in its old grid slot, querying the new gauge (re-import after deploy).Trade-offs vs the old metric: count resets on deploy (in-memory), no per-user breakdown (explicitly not wanted anymore).
Test plan
tests/server/test_metrics.py: window counting (1h vs 24h boundaries, repeat visits dedupe), stale-entry pruning.🤖 Generated with Claude Code