unleash-server/dist/lib/util/metrics/createGauge.d.ts

Unleash is an enterprise ready feature flag service. It provides different strategies for handling feature flags.

import { Gauge as PromGauge, type GaugeConfiguration } from 'prom-client';
/**
 * A wrapped instance of prom-client's Gauge, overriding some of its methods for enhanced functionality and type-safety.
 */
export type Gauge<T extends string = string> = {
    gauge: PromGauge<T>;
    labels: (labels: Record<T, string | number>) => PromGauge.Internal<T>;
    reset: () => void;
    set: (value: number) => void;
};
/**
 * Additional options for createGauge that allow registering a lazy collect function
 * which caches values for a given TTL.
 */
export type CreateGaugeOptions<T extends string> = GaugeConfiguration<T> & {
    /**
     * Time to live for cached values in milliseconds. Used together with `fetchValue`.
     */
    ttlMs?: number;
    /**
     * Optional fetcher used to populate the gauge value lazily on scrape.
     * If provided together with `ttlMs`, a `collect` function will be installed that
     * caches the value for the TTL. Return null to indicate unknown (we'll set NaN).
     */
    fetchValue?: () => Promise<number | null>;
};
/**
 * Creates a wrapped instance of prom-client's Gauge, overriding some of its methods for enhanced functionality and type-safety.
 *
 * @param options - The configuration options for the Gauge, as defined in prom-client's GaugeConfiguration.
 *               See prom-client documentation for detailed options: https://github.com/siimon/prom-client#gauge
 * @returns An object containing the wrapped Gauge instance and custom methods.
 */
export declare const createGauge: <T extends string>(options: CreateGaugeOptions<T>) => Gauge<T>;
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