SnapshotStore <T>

A time-pruning, time-windowed store for LoadSnapshot values. All four built-in signals compose with one of these, and so can yours — it is the only part of their machinery worth reusing.

Index

Constructors

• constructor

Methods

• clear
• getAll
• getSample
• push
• useSampleWindow

Constructors

constructor

• new SnapshotStore<T>(): SnapshotStore<T>

• Returns SnapshotStore<T>

Methods

clear

• clear(): void

• Discards every retained snapshot. The built-in signals do this when they start, so that a session neither samples nor diffs against measurements from before the preceding downtime — pruning is relative to the newest snapshot rather than the wall clock, so stale entries would otherwise survive indefinitely. Clearing on start rather than on stop leaves a finished session readable.

  ---

  Returns void

getAll

• getAll(): T[]

• Direct, unwindowed access to the underlying array — used by signals whose handler needs the previous snapshot to compute a delta (e.g. the event loop and storage backend signals read the last entry to measure change since it).

  ---

  Returns T[]

getSample

• getSample(sampleDurationMillis): T[]

• Return all snapshots, or only those within the given time window.

  ---

  Parameters

  • optionalsampleDurationMillis: number

  Returns T[]

push

• push(snapshot, now): void

• Add a snapshot and prune entries older than the history window.

  ---

  Parameters

  • snapshot: T

  • now: Date = snapshot.createdAt

  Returns void

useSampleWindow

• useSampleWindow(maxSampleWindowMillis): void

• Sizes retention to the window the signal will be sampled over, as handed to it in start(). Until this is called nothing is pruned at all, so a signal that ignores its start context grows unboundedly.

  ---

  Parameters

  • maxSampleWindowMillis: number

  Returns void