Overhaul stats: Emit events from the torrent-repository package and collect metrics

[josecelano]

Emit events from the torrent-repository package and collect metrics. In this PR, I'm only planning to include four metrics. The ones we have in the current stats endpoint:

{
  "torrents": 387044,
  "seeders": 183887,
  "completed": 1260584,
  "leechers": 249136,
}

However, I will rename them to:

{
  "torrent_repository_per_session_all_instances_all_torrents_total": 387044,
  "torrent_repository_per_session_all_instances_all_seeders_total": 183887,
  "torrent_repository_per_session_all_instances_all_torrents_downloads_total": 1260584,
  "torrent_repository_per_session_all_instances_all_leechers_total": 249136,
}

UPDATE: I will not use those long names but "labels". It's only to explain what they represent.

• per session: since the main tracker process started.
• all instances: all tracker servers (UDP or HTTP) running on different ports.
• all torrents: all swarms.

Becuase the current names are too ambiguous. See #1502 (comment).

How to test

1. Run the tracker.
2. Use the tracker client to make an announce request.

cargo run -p torrust-tracker-client --bin udp_tracker_client announce udp://127.0.0.1:6969 443c7602b4fde83d1154d6d9da48808418b181b6 | jq

3. Use the REST API to get the metric value.

curl -s "http://localhost:1212/api/v1/metrics?token=MyAccessToken&format=prometheus" | grep torrent_repository_peers_total

Subtasks

• Add basic event scaffolding in the torrent-respository package.
• Run the event listener for the torrent-repository package when the tracker starts.
  • Add the TorrentRepositoryContainer and run the listener when the tracker starts.
  • In production code: use the Swarms service provided by the TorrentRepositoryContainer in the TrackerCoreContainer (otherwise they will be unrelated).
  • In testing code: use the Swarms service provided by the TorrentRepositoryContainer in the TrackerCoreContainer (otherwise they will be unrelated).
• Expose the new metrics via the metrics API endpoint (even if it will have no value yet).
• Inject the event sender in Swarms and Swarm type to be able to send events from them.
  • In Swarms type.
  • In Swarm type.
• Allow incrementing/decrementing gauge metrics. #1516
• Star triggering events and process them to update the metrics in the metrics collection. One event and the corresponding affected metrics at the time.
  • TorrentAdded -> Increase torrents counter (all instances, all torrents)
  • Torrentremoved -> Decrease torrents counter (all instances, all torrents)
  • PeerAdded -> Increase peers counter (total, seeders, leechers)
  • PeerRemoved -> Decrease peers counter (total, seeders, leechers)
  • PeerUdpated -> Decrease peers counter (total, seeders, leechers)
  • PeerDownloadCompleted -> Increase torrent downloads counter (all instances, all torrents)
• Add tests to check that events have been sent.
• Add tests to check that metrics are updated after receiving the event.

[codecov]

Codecov Report

Attention: Patch coverage is 93.00380% with 92 lines in your changes missing coverage. Please review.

Project coverage is 84.35%. Comparing base (93fdf31) to head (d154b2a).
Report is 27 commits behind head on develop.

Files with missing lines	Patch %	Lines
packages/primitives/src/peer.rs	32.72%	37 Missing ⚠️
...orrent-repository/src/statistics/event/listener.rs	52.00%	11 Missing and 1 partial ⚠️
...kages/torrent-repository/src/statistics/metrics.rs	72.72%	9 Missing ⚠️
...torrent-repository/src/statistics/event/handler.rs	94.80%	0 Missing and 8 partials ⚠️
packages/events/src/bus.rs	68.42%	6 Missing ⚠️
...es/torrent-repository/src/statistics/repository.rs	88.46%	6 Missing ⚠️
...s/rest-tracker-api-core/src/statistics/services.rs	28.57%	5 Missing ⚠️
packages/udp-tracker-server/src/environment.rs	62.50%	3 Missing ⚠️
...racker-api-server/src/v1/context/stats/handlers.rs	0.00%	2 Missing ⚠️
src/bootstrap/jobs/torrent_repository.rs	77.77%	2 Missing ⚠️
... and 2 more

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1513      +/-   ##
===========================================
+ Coverage    83.75%   84.35%   +0.59%     
===========================================
  Files          257      265       +8     
  Lines        18049    18933     +884     
  Branches     18049    18933     +884     
===========================================
+ Hits         15117    15970     +853     
- Misses        2654     2682      +28     
- Partials       278      281       +3     

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[josecelano]

ACK d154b2a