Struct HistoryWindow 

pub struct HistoryWindow<'a> { /* private fields */ }

A ring plus the cursor into it that a rule evaluates against.

Implementations

impl<'a> HistoryWindow<'a>

pub const fn new(ring: &'a HistoryRing, view: HistoryView) -> Self

Pairs a ring with an explicit cursor.

pub const fn live(ring: &'a HistoryRing) -> Self

Pairs a ring with a cursor following the newest sample.

pub const fn view(&self) -> HistoryView

The cursor, which is the HistoryView §11.1’s sketch passes.

pub const fn ring(&self) -> &'a HistoryRing

The ring being read.

pub fn expected_interval(&self) -> Duration

The interval history is configured to retain samples at (§8.5).

Rules that need a reference interval use this rather than assuming one second (§8.1).

pub fn selected(&self) -> Option<&'a HistoricalSample>

The sample the cursor selects, or the newest one when live.

pub fn len(&self) -> usize

How many samples are retained in total.

pub fn is_empty(&self) -> bool

Whether no sample has been recorded yet.

pub fn recent( &self, count: usize, ) -> impl DoubleEndedIterator<Item = &'a HistoricalSample>

The count samples ending at the cursor, oldest first.

Resolved by absolute index, so it costs one deque lookup per sample and never scans the ring (§21 M4).

pub fn previous_sample(&self, sequence: u64) -> Option<&'a HistoricalSample>

The newest retained sample strictly older than sequence.

Rules that compare “now” against “the previous sample” use this so they work whether or not the snapshot under evaluation has already been recorded into the ring.

pub fn count_where( &self, metric: HistoryMetric, count: usize, predicate: impl Fn(f64) -> bool, ) -> Counted

Counts how many of the count most recent samples satisfy predicate.

predicate sees only freshly measured values: a sample whose metric was unavailable is tallied in Counted::unavailable and never passed to the predicate, so no rule can accidentally treat a missing reading as a zero (§26).

pub fn count_at_least( &self, metric: HistoryMetric, count: usize, threshold: f64, ) -> Counted

Counts how many of the count most recent samples are at or above threshold.

pub fn trend( &self, metric: HistoryMetric, count: usize, ) -> Option<(f64, f64, Duration)>

The oldest and newest freshly measured values of metric in the window.

Returns None unless both ends were measured, because a trend computed against a missing endpoint is a fabrication (§26). The returned duration is the real span between the two samples, never an assumed one (§8.1).

Trait Implementations

impl<'a> Clone for HistoryWindow<'a>

fn clone(&self) -> HistoryWindow<'a>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<'a> Copy for HistoryWindow<'a>

impl<'a> Debug for HistoryWindow<'a>

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

Formats the value using the given formatter.