perf_hooks.d.ts

/**
 * This module provides an implementation of a subset of the W3C[Web Performance APIs](https://w3c.github.io/perf-timing-primer/) as well as additional APIs for
 * Node.js-specific performance measurements.
 *
 * Node.js supports the following [Web Performance APIs](https://w3c.github.io/perf-timing-primer/):
 *
 * * [High Resolution Time](https://www.w3.org/TR/hr-time-2)
 * * [Performance Timeline](https://w3c.github.io/performance-timeline/)
 * * [User Timing](https://www.w3.org/TR/user-timing/)
 *
 * ```js
 * const { PerformanceObserver, performance } = require('perf_hooks');
 *
 * const obs = new PerformanceObserver((items) => {
 *   console.log(items.getEntries()[0].duration);
 *   performance.clearMarks();
 * });
 * obs.observe({ type: 'measure' });
 * performance.measure('Start to Now');
 *
 * performance.mark('A');
 * doSomeLongRunningProcess(() => {
 *   performance.measure('A to Now', 'A');
 *
 *   performance.mark('B');
 *   performance.measure('A to B', 'A', 'B');
 * });
 * ```
 * @see [source](https://github.com/nodejs/node/blob/v16.7.0/lib/perf_hooks.js)
 */
declare module 'perf_hooks' {
    import { AsyncResource } from 'node:async_hooks';
    type EntryType = 'node' | 'mark' | 'measure' | 'gc' | 'function' | 'http2' | 'http';
    interface NodeGCPerformanceDetail {
        /**
         * When `performanceEntry.entryType` is equal to 'gc', `the performance.kind` property identifies
         * the type of garbage collection operation that occurred.
         * See perf_hooks.constants for valid values.
         */
        readonly kind?: number | undefined;
        /**
         * When `performanceEntry.entryType` is equal to 'gc', the `performance.flags`
         * property contains additional information about garbage collection operation.
         * See perf_hooks.constants for valid values.
         */
        readonly flags?: number | undefined;
    }
    /**
     * @since v8.5.0
     */
    class PerformanceEntry {
        protected constructor();
        /**
         * The total number of milliseconds elapsed for this entry. This value will not
         * be meaningful for all Performance Entry types.
         * @since v8.5.0
         */
        readonly duration: number;
        /**
         * The name of the performance entry.
         * @since v8.5.0
         */
        readonly name: string;
        /**
         * The high resolution millisecond timestamp marking the starting time of the
         * Performance Entry.
         * @since v8.5.0
         */
        readonly startTime: number;
        /**
         * The type of the performance entry. It may be one of:
         *
         * * `'node'` (Node.js only)
         * * `'mark'` (available on the Web)
         * * `'measure'` (available on the Web)
         * * `'gc'` (Node.js only)
         * * `'function'` (Node.js only)
         * * `'http2'` (Node.js only)
         * * `'http'` (Node.js only)
         * @since v8.5.0
         */
        readonly entryType: EntryType;
        /**
         * Additional detail specific to the `entryType`.
         * @since v16.0.0
         */
        readonly detail?: NodeGCPerformanceDetail | unknown | undefined; // TODO: Narrow this based on entry type.
    }
    /**
     * _This property is an extension by Node.js. It is not available in Web browsers._
     *
     * Provides timing details for Node.js itself. The constructor of this class
     * is not exposed to users.
     * @since v8.5.0
     */
    class PerformanceNodeTiming extends PerformanceEntry {
        /**
         * The high resolution millisecond timestamp at which the Node.js process
         * completed bootstrapping. If bootstrapping has not yet finished, the property
         * has the value of -1.
         * @since v8.5.0
         */
        readonly bootstrapComplete: number;
        /**
         * The high resolution millisecond timestamp at which the Node.js environment was
         * initialized.
         * @since v8.5.0
         */
        readonly environment: number;
        /**
         * The high resolution millisecond timestamp of the amount of time the event loop
         * has been idle within the event loop's event provider (e.g. `epoll_wait`). This
         * does not take CPU usage into consideration. If the event loop has not yet
         * started (e.g., in the first tick of the main script), the property has the
         * value of 0.
         * @since v14.10.0, v12.19.0
         */
        readonly idleTime: number;
        /**
         * The high resolution millisecond timestamp at which the Node.js event loop
         * exited. If the event loop has not yet exited, the property has the value of -1\.
         * It can only have a value of not -1 in a handler of the `'exit'` event.
         * @since v8.5.0
         */
        readonly loopExit: number;
        /**
         * The high resolution millisecond timestamp at which the Node.js event loop
         * started. If the event loop has not yet started (e.g., in the first tick of the
         * main script), the property has the value of -1.
         * @since v8.5.0
         */
        readonly loopStart: number;
        /**
         * The high resolution millisecond timestamp at which the V8 platform was
         * initialized.
         * @since v8.5.0
         */
        readonly v8Start: number;
    }
    interface EventLoopUtilization {
        idle: number;
        active: number;
        utilization: number;
    }
    /**
     * @param util1 The result of a previous call to eventLoopUtilization()
     * @param util2 The result of a previous call to eventLoopUtilization() prior to util1
     */
    type EventLoopUtilityFunction = (util1?: EventLoopUtilization, util2?: EventLoopUtilization) => EventLoopUtilization;
    interface MarkOptions {
        /**
         * Additional optional detail to include with the mark.
         */
        detail?: unknown | undefined;
        /**
         * An optional timestamp to be used as the mark time.
         * @default `performance.now()`.
         */
        startTime?: number | undefined;
    }
    interface MeasureOptions {
        /**
         * Additional optional detail to include with the mark.
         */
        detail?: unknown | undefined;
        /**
         * Duration between start and end times.
         */
        duration?: number | undefined;
        /**
         * Timestamp to be used as the end time, or a string identifying a previously recorded mark.
         */
        end?: number | string | undefined;
        /**
         * Timestamp to be used as the start time, or a string identifying a previously recorded mark.
         */
        start?: number | string | undefined;
    }
    interface TimerifyOptions {
        /**
         * A histogram object created using
         * `perf_hooks.createHistogram()` that will record runtime durations in
         * nanoseconds.
         */
        histogram?: RecordableHistogram | undefined;
    }
    interface Performance {
        /**
         * If name is not provided, removes all PerformanceMark objects from the Performance Timeline.
         * If name is provided, removes only the named mark.
         * @param name
         */
        clearMarks(name?: string): void;
        /**
         * Creates a new PerformanceMark entry in the Performance Timeline.
         * A PerformanceMark is a subclass of PerformanceEntry whose performanceEntry.entryType is always 'mark',
         * and whose performanceEntry.duration is always 0.
         * Performance marks are used to mark specific significant moments in the Performance Timeline.
         * @param name
         */
        mark(name?: string, options?: MarkOptions): void;
        /**
         * Creates a new PerformanceMeasure entry in the Performance Timeline.
         * A PerformanceMeasure is a subclass of PerformanceEntry whose performanceEntry.entryType is always 'measure',
         * and whose performanceEntry.duration measures the number of milliseconds elapsed since startMark and endMark.
         *
         * The startMark argument may identify any existing PerformanceMark in the the Performance Timeline, or may identify
         * any of the timestamp properties provided by the PerformanceNodeTiming class. If the named startMark does not exist,
         * then startMark is set to timeOrigin by default.
         *
         * The endMark argument must identify any existing PerformanceMark in the the Performance Timeline or any of the timestamp
         * properties provided by the PerformanceNodeTiming class. If the named endMark does not exist, an error will be thrown.
         * @param name
         * @param startMark
         * @param endMark
         */
        measure(name: string, startMark?: string, endMark?: string): void;
        measure(name: string, options: MeasureOptions): void;
        /**
         * An instance of the PerformanceNodeTiming class that provides performance metrics for specific Node.js operational milestones.
         */
        readonly nodeTiming: PerformanceNodeTiming;
        /**
         * @return the current high resolution millisecond timestamp
         */
        now(): number;
        /**
         * The timeOrigin specifies the high resolution millisecond timestamp from which all performance metric durations are measured.
         */
        readonly timeOrigin: number;
        /**
         * Wraps a function within a new function that measures the running time of the wrapped function.
         * A PerformanceObserver must be subscribed to the 'function' event type in order for the timing details to be accessed.
         * @param fn
         */
        timerify<T extends (...params: any[]) => any>(fn: T, options?: TimerifyOptions): T;
        /**
         * eventLoopUtilization is similar to CPU utilization except that it is calculated using high precision wall-clock time.
         * It represents the percentage of time the event loop has spent outside the event loop's event provider (e.g. epoll_wait).
         * No other CPU idle time is taken into consideration.
         */
        eventLoopUtilization: EventLoopUtilityFunction;
    }
    interface PerformanceObserverEntryList {
        /**
         * Returns a list of `PerformanceEntry` objects in chronological order
         * with respect to `performanceEntry.startTime`.
         *
         * ```js
         * const {
         *   performance,
         *   PerformanceObserver
         * } = require('perf_hooks');
         *
         * const obs = new PerformanceObserver((perfObserverList, observer) => {
         *   console.log(perfObserverList.getEntries());
         *
         *    * [
         *    *   PerformanceEntry {
         *    *     name: 'test',
         *    *     entryType: 'mark',
         *    *     startTime: 81.465639,
         *    *     duration: 0
         *    *   },
         *    *   PerformanceEntry {
         *    *     name: 'meow',
         *    *     entryType: 'mark',
         *    *     startTime: 81.860064,
         *    *     duration: 0
         *    *   }
         *    * ]
         *
         *   observer.disconnect();
         * });
         * obs.observe({ type: 'mark' });
         *
         * performance.mark('test');
         * performance.mark('meow');
         * ```
         * @since v8.5.0
         */
        getEntries(): PerformanceEntry[];
        /**
         * Returns a list of `PerformanceEntry` objects in chronological order
         * with respect to `performanceEntry.startTime` whose `performanceEntry.name` is
         * equal to `name`, and optionally, whose `performanceEntry.entryType` is equal to`type`.
         *
         * ```js
         * const {
         *   performance,
         *   PerformanceObserver
         * } = require('perf_hooks');
         *
         * const obs = new PerformanceObserver((perfObserverList, observer) => {
         *   console.log(perfObserverList.getEntriesByName('meow'));
         *
         *    * [
         *    *   PerformanceEntry {
         *    *     name: 'meow',
         *    *     entryType: 'mark',
         *    *     startTime: 98.545991,
         *    *     duration: 0
         *    *   }
         *    * ]
         *
         *   console.log(perfObserverList.getEntriesByName('nope')); // []
         *
         *   console.log(perfObserverList.getEntriesByName('test', 'mark'));
         *
         *    * [
         *    *   PerformanceEntry {
         *    *     name: 'test',
         *    *     entryType: 'mark',
         *    *     startTime: 63.518931,
         *    *     duration: 0
         *    *   }
         *    * ]
         *
         *   console.log(perfObserverList.getEntriesByName('test', 'measure')); // []
         *   observer.disconnect();
         * });
         * obs.observe({ entryTypes: ['mark', 'measure'] });
         *
         * performance.mark('test');
         * performance.mark('meow');
         * ```
         * @since v8.5.0
         */
        getEntriesByName(name: string, type?: EntryType): PerformanceEntry[];
        /**
         * Returns a list of `PerformanceEntry` objects in chronological order
         * with respect to `performanceEntry.startTime` whose `performanceEntry.entryType`is equal to `type`.
         *
         * ```js
         * const {
         *   performance,
         *   PerformanceObserver
         * } = require('perf_hooks');
         *
         * const obs = new PerformanceObserver((perfObserverList, observer) => {
         *   console.log(perfObserverList.getEntriesByType('mark'));
         *
         *    * [
         *    *   PerformanceEntry {
         *    *     name: 'test',
         *    *     entryType: 'mark',
         *    *     startTime: 55.897834,
         *    *     duration: 0
         *    *   },
         *    *   PerformanceEntry {
         *    *     name: 'meow',
         *    *     entryType: 'mark',
         *    *     startTime: 56.350146,
         *    *     duration: 0
         *    *   }
         *    * ]
         *
         *   observer.disconnect();
         * });
         * obs.observe({ type: 'mark' });
         *
         * performance.mark('test');
         * performance.mark('meow');
         * ```
         * @since v8.5.0
         */
        getEntriesByType(type: EntryType): PerformanceEntry[];
    }
    type PerformanceObserverCallback = (list: PerformanceObserverEntryList, observer: PerformanceObserver) => void;
    class PerformanceObserver extends AsyncResource {
        constructor(callback: PerformanceObserverCallback);
        /**
         * Disconnects the `PerformanceObserver` instance from all notifications.
         * @since v8.5.0
         */
        disconnect(): void;
        /**
         * Subscribes the `PerformanceObserver` instance to notifications of new `PerformanceEntry` instances identified either by `options.entryTypes`or `options.type`:
         *
         * ```js
         * const {
         *   performance,
         *   PerformanceObserver
         * } = require('perf_hooks');
         *
         * const obs = new PerformanceObserver((list, observer) => {
         *   // Called three times synchronously. `list` contains one item.
         * });
         * obs.observe({ type: 'mark' });
         *
         * for (let n = 0; n < 3; n++)
         *   performance.mark(`test${n}`);
         * ```
         * @since v8.5.0
         */
        observe(
            options:
                | {
                      entryTypes: ReadonlyArray<EntryType>;
                  }
                | {
                      type: EntryType;
                  }
        ): void;
    }
    namespace constants {
        const NODE_PERFORMANCE_GC_MAJOR: number;
        const NODE_PERFORMANCE_GC_MINOR: number;
        const NODE_PERFORMANCE_GC_INCREMENTAL: number;
        const NODE_PERFORMANCE_GC_WEAKCB: number;
        const NODE_PERFORMANCE_GC_FLAGS_NO: number;
        const NODE_PERFORMANCE_GC_FLAGS_CONSTRUCT_RETAINED: number;
        const NODE_PERFORMANCE_GC_FLAGS_FORCED: number;
        const NODE_PERFORMANCE_GC_FLAGS_SYNCHRONOUS_PHANTOM_PROCESSING: number;
        const NODE_PERFORMANCE_GC_FLAGS_ALL_AVAILABLE_GARBAGE: number;
        const NODE_PERFORMANCE_GC_FLAGS_ALL_EXTERNAL_MEMORY: number;
        const NODE_PERFORMANCE_GC_FLAGS_SCHEDULE_IDLE: number;
    }
    const performance: Performance;
    interface EventLoopMonitorOptions {
        /**
         * The sampling rate in milliseconds.
         * Must be greater than zero.
         * @default 10
         */
        resolution?: number | undefined;
    }
    interface Histogram {
        /**
         * Returns a `Map` object detailing the accumulated percentile distribution.
         * @since v11.10.0
         */
        readonly percentiles: Map<number, number>;
        /**
         * The number of times the event loop delay exceeded the maximum 1 hour event
         * loop delay threshold.
         * @since v11.10.0
         */
        readonly exceeds: number;
        /**
         * The minimum recorded event loop delay.
         * @since v11.10.0
         */
        readonly min: number;
        /**
         * The maximum recorded event loop delay.
         * @since v11.10.0
         */
        readonly max: number;
        /**
         * The mean of the recorded event loop delays.
         * @since v11.10.0
         */
        readonly mean: number;
        /**
         * The standard deviation of the recorded event loop delays.
         * @since v11.10.0
         */
        readonly stddev: number;
        /**
         * Resets the collected histogram data.
         * @since v11.10.0
         */
        reset(): void;
        /**
         * Returns the value at the given percentile.
         * @since v11.10.0
         * @param percentile A percentile value in the range (0, 100].
         */
        percentile(percentile: number): number;
    }
    interface IntervalHistogram extends Histogram {
        /**
         * Enables the update interval timer. Returns `true` if the timer was
         * started, `false` if it was already started.
         * @since v11.10.0
         */
        enable(): boolean;
        /**
         * Disables the update interval timer. Returns `true` if the timer was
         * stopped, `false` if it was already stopped.
         * @since v11.10.0
         */
        disable(): boolean;
    }
    interface RecordableHistogram extends Histogram {
        /**
         * @since v15.9.0
         * @param val The amount to record in the histogram.
         */
        record(val: number | bigint): void;
        /**
         * Calculates the amount of time (in nanoseconds) that has passed since the
         * previous call to `recordDelta()` and records that amount in the histogram.
         *
         * ## Examples
         * @since v15.9.0
         */
        recordDelta(): void;
    }
    /**
     * _This property is an extension by Node.js. It is not available in Web browsers._
     *
     * Creates an `IntervalHistogram` object that samples and reports the event loop
     * delay over time. The delays will be reported in nanoseconds.
     *
     * Using a timer to detect approximate event loop delay works because the
     * execution of timers is tied specifically to the lifecycle of the libuv
     * event loop. That is, a delay in the loop will cause a delay in the execution
     * of the timer, and those delays are specifically what this API is intended to
     * detect.
     *
     * ```js
     * const { monitorEventLoopDelay } = require('perf_hooks');
     * const h = monitorEventLoopDelay({ resolution: 20 });
     * h.enable();
     * // Do something.
     * h.disable();
     * console.log(h.min);
     * console.log(h.max);
     * console.log(h.mean);
     * console.log(h.stddev);
     * console.log(h.percentiles);
     * console.log(h.percentile(50));
     * console.log(h.percentile(99));
     * ```
     * @since v11.10.0
     */
    function monitorEventLoopDelay(options?: EventLoopMonitorOptions): IntervalHistogram;
    interface CreateHistogramOptions {
        /**
         * The minimum recordable value. Must be an integer value greater than 0.
         * @default 1
         */
        min?: number | bigint | undefined;
        /**
         * The maximum recordable value. Must be an integer value greater than min.
         * @default Number.MAX_SAFE_INTEGER
         */
        max?: number | bigint | undefined;
        /**
         * The number of accuracy digits. Must be a number between 1 and 5.
         * @default 3
         */
        figures?: number | undefined;
    }
    /**
     * Returns a `RecordableHistogram`.
     * @since v15.9.0
     */
    function createHistogram(options?: CreateHistogramOptions): RecordableHistogram;
}
declare module 'node:perf_hooks' {
    export * from 'perf_hooks';
}