Files
buzz/docs/usage-metrics.md
Luke Tornquist 506a588f88 refactor(relay): remove database usage-metric queries (#9040)
## Summary

The relay no longer runs database aggregate queries to emit usage
gauges. Fleet and per-community counts of users, channels, relay
members, workflows, git repos, communities, messages, and active
users/channels are no longer relay metrics, and neither are the snapshot
health gauges that came with them.

### Removed

- **Gauges:** `buzz_total_users`, `buzz_total_channels`,
`buzz_total_relay_members`, `buzz_total_workflows`,
`buzz_total_git_repos`, `buzz_total_active_users`,
`buzz_total_messages`, `buzz_total_active_channels`,
`buzz_communities_estimated` / `buzz_communities_total`, and every
DB-derived `buzz_community_*` series (users, channels, messages, relay
members, workflows, git repos, active users, active channels).
- **Per-community mode:** `BUZZ_USAGE_METRICS_PER_COMMUNITY=all` and
everything it fed: the per-community in-memory gauges,
`buzz_community_storage_bytes` / `buzz_community_storage_objects`,
`buzz_storage_unmapped_community_bytes`, the community → host map query,
and the emission-scope bookkeeping that cleared series for renamed or
removed communities. No deployment set it. If one still does, the relay
ignores it.
- **Health signals:** `buzz_usage_snapshot_available`,
`buzz_usage_snapshot_age_seconds`, `buzz_usage_query_skipped_total`, and
the `usage_fleet_*` paths of `buzz_db_route_decision`.
- **Code and config:**
  - `buzz-db/src/store/usage.rs`, including its aggregate queries.
- The relay's `FleetUsageSchedule` and its cadence/deadline/retry
machinery.
  - The replica-only telemetry route (`Db::route_usage_read`).
- `BUZZ_USAGE_METRICS_REPLICA_MAX_AGE_MS` and
`DbConfig::usage_metrics_replica_max_age_ms`. If a deployment still sets
the env var, the relay now ignores it; startup doesn't fail.
- **Reader maintenance pool operation:** `ReaderOperation::Maintenance`
and its `close_on_drop` release path existed only for those telemetry
reads, so they're removed too. The pool-acquire contract drops from
twelve to eleven valid pairs, which lowers the per-pod series ceiling
from 216 to 198.
- **Dead code:** `Db::active_community_hosts` had no callers.

### Kept

- **Leader:** the usage poller's leader lock, plus the leader's invite
reaping and fleet storage-snapshot gauges. The session advisory lock
(`SessionLeader`, `Db::try_lock_session_leader`) moves to
`buzz-db/src/store/leader_lock.rs`, since storage-usage delivery uses it
too and it has nothing to do with usage queries.
- **In-memory gauges:** pod-local connection, subscription, and
online-user gauges. They read process state, not the database.
- **Writer maintenance pool operation:** `WriterOperation::Maintenance`
stays. Dozens of writer-side maintenance paths across `buzz-db` use it
(reapers, retention, the leader lock). The reader variant only ever
served the telemetry reads.
- **Storage-usage delivery:** unchanged. It reads the storage snapshot
for billing, not for metrics.

`docs/usage-metrics.md`, `docs/storage-accounting.md`, `.env.example`,
and the Helm chart README are updated to match.

## What got simpler

This is net deletion (~3.6k lines). One telemetry subsystem is gone: two
collection families with independent cadences, availability and age
semantics, relay-side deadlines, a dedicated replica routing policy, two
config knobs, a per-community emission mode, and a pool-operation
variant. Leader election now does only leader work, and it lives in its
own module.

## Operational note

Dashboards and monitors that read the removed series will go to no data
once this rolls out.

## Testing

- `cargo fmt --check`, workspace `cargo clippy --all-targets -D
warnings`.
- `buzz-db` lib, `observability_source`, and doc tests.
- `buzz-relay` lib tests.
- The Postgres lane for `buzz-db` (lib + tests) and `buzz-relay` (lib).

All of these run on a remote workstation at the PR head.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Signed-off-by: Luke Tornquist <tornquist@squareup.com>
Co-authored-by: Elrond <28d6302a099e5225b02c4155ac4236e4912603df2ab08dbfc2f4fef08ce598c8@buzz.block.builderlab.xyz>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
2026-11-04 22:00:30 -05:00

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Markdown

# Usage metrics operations
The relay runs no database aggregate queries for usage telemetry, and it emits
no per-community usage series. Its usage poller emits pod-local in-memory
gauges and republishes fleet totals from the stored storage snapshot. Fleet
counts of users, channels, members, workflows, repositories, and active users
are not relay metrics.
## In-memory gauges
Every pod exports its own `buzz_total_ws_connections`,
`buzz_total_users_online_pod`, and `buzz_total_subscriptions`. They come from
live process state, so dashboards aggregate them with `sum()` across pods.
## Storage gauges
Storage totals come from the `buzz-admin` worker snapshot and carry their own
`buzz_storage_snapshot_load_ok` and `buzz_storage_snapshot_age_seconds` health
gauges; see [storage-accounting.md](storage-accounting.md). Storage gauges are
leader-only: in a multi-pod deployment, first filter them to the pod where
`buzz_usage_poller_is_leader == 1`; do not take an unfiltered maximum across
pods.
## Leader election
Every relay process attempts the same PostgreSQL session advisory lock. Exactly
one live database session owns it. The leader reaps expired relay invites and
publishes the storage gauges. If that process or session exits, PostgreSQL
releases the lock and another relay acquires it.