Map scheduler metrics

What the maps record about their ticks, who sees whom and the movement relay, on the meter NexusTomorrow.Maps. How maps are ticked is on Map scheduler.

The metrics

Metric	Kind	Unit	Tagged by	Records
nexustomorrow.map.ticks	counter		world	Each tick a map completes
nexustomorrow.map.tick.duration	histogram	ms	world	How long each tick took
nexustomorrow.map.tick.allocated	histogram	bytes	world	What each tick allocated
nexustomorrow.map.ticks_skipped	counter			Deadlines passed over because a tick ran long
nexustomorrow.map.faults	counter		world, inside a map	A tick that threw, and a handler or timer that threw inside a map
nexustomorrow.map.dropped	counter		world	Client messages a map read but didn't act on
nexustomorrow.map.units_admitted	counter		world	Players created for a viewer that came into range
nexustomorrow.map.units_dropped	counter		world	Players destroyed for a viewer: out of range, hidden or gone
nexustomorrow.map.batches_relayed	counter		world	Movement batches relayed to the players who see the mover
nexustomorrow.map.batches_dropped	counter		world, reason	Movement batches dropped: older, too_long, ring_full or refused (Owners map)

The world tag is the world's id, and the reason tag says why a batch was dropped. Recording allocates nothing while nothing listens.

What healthy looks like

At the default 25 ms tick, each map completes 40 ticks a second, ticks_skipped stays at or near 0, and a steady tick allocates 0 bytes, with players moving. batches_dropped stays low: a climb in ring_full means batches arrive faster than the map flushes them, and any refused is a declaration defect. Running a server has how to watch them.

Known edges

• A fault counted by the scheduler, a whole tick that threw, carries no world tag; faults inside a map do.

Where the code lives

Piece	Path
The meter and its instruments	Source/NexusTomorrow.Maps/MapMetrics.cs
Where a tick is measured	Source/NexusTomorrow.Maps/MapOwner.cs
Where units and batches are counted	Source/NexusTomorrow.Maps/Visibility/AreaOfInterest.cs, Source/NexusTomorrow.Maps/Movement/MovementRelay.cs