Struct MetricsSnapshot 

#[non_exhaustive]
pub struct MetricsSnapshot {
    pub turns: u64,
    pub depth_samples: u64,
    pub high_depth_mean: f64,
    pub high_depth_max: u64,
    pub low_depth_mean: f64,
    pub low_depth_max: u64,
    pub longest: Option<(CommandKind, Duration)>,
    pub low_starved_turns: u64,
    pub low_starved_run_max: u64,
    pub kinds: Vec<KindSnapshot>,
}

What the actor has done since the database was opened.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

turns: u64

Commands executed, i.e. the sum of KindSnapshot::turns. The two agree by construction rather than by coincidence.

depth_samples: u64

Loop iterations that took a queue-depth reading. Always at least turns + 1 on a live actor, because the reading is taken on the way in to a select! that has not resolved yet. This is the denominator of the two means below, and it is exposed so the difference is visible rather than looking like drift.

high_depth_mean: f64

high_depth_max: u64

low_depth_mean: f64

low_depth_max: u64

longest: Option<(CommandKind, Duration)>

The longest hold since open and what caused it. None before the first turn, and — honestly — also when every turn so far took under a microsecond, which on this path does not happen.

low_starved_turns: u64

Turns spent on high-priority work while low-priority work was already queued (0.12.10, W4.4, D-153).

The actor’s select! is biased and has no floor, so this is the measurement of a bound the design has always had and never observed. On its own it is not alarming: a busy database should prefer interactive writes, and this counter rising is that working. Read it beside Self::low_starved_run_max, which is the number with teeth.

low_starved_run_max: u64

The longest unbroken run of the above — i.e. the most turns any single low-priority command has waited (0.12.10, W4.4, D-153).

This is the one that answers “can low-priority work be starved”. A large low_starved_turns spread over a long session says the tiers are doing their job; a large run says one specific chunk, rebuild or archive sat behind that many interactive writes in a row.

There is deliberately no forced-yield policy attached to this. Adding one now would be fixing a bound nobody has observed being hit, and the counter exists precisely to find out whether it is. See D-153.

kinds: Vec<KindSnapshot>

Implementations

impl MetricsSnapshot

pub fn budget_violations(&self) -> Vec<&KindSnapshot>

Kinds that broke the budget, worst first. The one-line answer to “is the 3 ms bound holding?”.

Trait Implementations

impl Clone for MetricsSnapshot

fn clone(&self) -> MetricsSnapshot

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for MetricsSnapshot

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for MetricsSnapshot

fn eq(&self, other: &MetricsSnapshot) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for MetricsSnapshot