Minor Description
Currently, snapshot operations of excessive duration aren't necessarily obvious in e.g. the scheduler logs or dashboards. Since this is a potentially critical/dangerous operation (in some cases leading to zookeeper timeouts + scheduler suicide), it would be prudent to expose relevant information more readily (e.g. when the operations commence/complete, timing, etc)
From Zameer:
The doSnapshot method of LogStorage is timed with the key "scheduler_log_snapshot". These are the stats it produces:
scheduler_log_snapshot_events 19
scheduler_log_snapshot_events_per_sec 0.0
scheduler_log_snapshot_nanos_per_event 0.0
scheduler_log_snapshot_nanos_total 373115257383
scheduler_log_snapshot_nanos_total_per_sec 0.0
scheduler_log_snapshot_persist_events 19
scheduler_log_snapshot_persist_events_per_sec 0.0
scheduler_log_snapshot_persist_nanos_per_event 0.0
scheduler_log_snapshot_persist_nanos_total 339151517713
scheduler_log_snapshot_persist_nanos_total_per_sec 0.0
scheduler_log_snapshots 19Which metric should be tracked in our dashboard?
From Bill F:
a very long snapshot might never be reflected there if a suicide happens mid-way through. The minimal fix would be to just LOG when a snapshot is about to commence.