Add metrics tracking time to restore a database from disk #3285
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Add 5 new metrics: - `replay_total_time_seconds(db: Identity)`, total time to read and restore snapshot and replay commitlog. - `replay_snapshot_read_time_seconds(db: Identity)`, time to read snapshot from disk. - `replay_snapshot_restore_time_seconds(db: Identity)`, time to restore snapshot once it's already in memory. - `replay_commitlog_time_seconds(db: Identity)`, time to replay commitlog once snapshot is restored. - `replay_commitlog_num_commits(db: Identity)`, number of commits visited during commitlog replay, i.e. the length of the suffix after the most recent usable snapshot. All of these are `Gauge`s (or `IntGauge` for the `num_commits` metric), as we expect observations to be very infrequent (approx. once per label value per SpacetimeDB process).
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Description of Changes
Inspired by a question @Shubham8287 asked me: how long does it take to replay real production databases, e.g. a BitCraft region module? I did not have a good answer, and didn't know how I could get an answer.
Add 5 new metrics:
replay_total_time_seconds(db: Identity), total time to read and restore snapshot and replay commitlog.replay_snapshot_read_time_seconds(db: Identity), time to read snapshot from disk.replay_snapshot_restore_time_seconds(db: Identity), time to restore snapshot once it's already in memory.replay_commitlog_time_seconds(db: Identity), time to replay commitlog once snapshot is restored.replay_commitlog_num_commits(db: Identity), number of commits visited during commitlog replay, i.e. the length of the suffix after the most recent usable snapshot.All of these are
Gauges (orIntGaugefor thenum_commitsmetric), as we expect observations to be very infrequent(approx. once per label value per SpacetimeDB process).
API and ABI breaking changes
N/a
Expected complexity level and risk
1
Testing
I remain unsure how to test metrics. This won't break anything, though, so I'm not worried.