@mdf.js/service-registry/dist/observability/registries/metrics/MetricsFacade.d.ts

MMS - API - Service Registry

/**
 * Copyright 2024 Mytra Control S.L. All rights reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be found in the LICENSE file
 * or at https://opensource.org/licenses/MIT.
 */
import { Health, Layer } from '@mdf.js/core';
import EventEmitter from 'events';
import express from 'express';
import { Metric, MetricObjectWithValues, MetricValue, Registry } from 'prom-client';
import * as Metrics from './types';
import { MetricsRegistryOptions } from './types';
/**
 * MetricsFacade class serves as a facade to simplify metrics management across all services
 * in an application. It leverages the prom-client library for metrics management and the express
 * library to expose these metrics via an HTTP endpoint.
 *
 * It accommodates working in cluster environments by optionally creating a new AggregatorRegistry
 * to hold metrics from all worker nodes, in addition to a separate registry for
 * application-specific metrics and the default prom-client registry. Thus, it can manage up to
 * three different registries:
 *
 * 1. Default prom-client registry for default metrics.
 * 2. Application-specific metrics registry.
 * 3. Cluster-wide metrics registry for environments running in a cluster.
 *
 * Depending on the environment and the node type (primary or worker), it responds to metric
 * requests by merging and presenting metrics from appropriate registries.
 */
export declare class MetricsFacade extends EventEmitter implements Layer.App.Service {
    private readonly options;
    /** Debug logger for development and deep troubleshooting */
    private readonly logger;
    /** Metrics aggregator */
    private readonly aggregator;
    /** Metrics aggregator registry */
    private readonly port;
    /** Metrics router */
    private readonly _router;
    /**
     * Create an instance of metrics manager
     * @param options - Configuration options for the metrics manager
     */
    constructor(options: MetricsRegistryOptions);
    /**
     * Conditionally creates an AggregatorRegistry if the service is running in a cluster.
     * @param isCluster - Boolean indicating if the service is running in cluster mode.
     * @returns An AggregatorRegistry instance or undefined if not in cluster mode.
     */
    private getPort;
    /** @returns The application name */
    get name(): string;
    /** @returns The application identifier */
    get componentId(): string;
    /** @returns An Express router with access to metrics information */
    get router(): express.Router;
    /** @returns Links offered by this service */
    get links(): {
        [link: string]: string;
    };
    /** @returns The health status of the component */
    get status(): Health.Status;
    /** @returns Health checks for this service */
    get checks(): Health.Checks;
    /**
     * Registers one or multiple services to be monitored.
     * @param services - A single service or an array of services to be registered.
     */
    register(services: Layer.App.Service | Layer.App.Service[]): void;
    /** @returns The registry used by the aggregator */
    get registry(): Registry;
    /** @returns Metrics in text/plain format */
    metricsText(): Promise<Metrics.Response>;
    /** @returns Metrics in JSON format */
    metricsJSON(): Promise<Metrics.Response>;
    /**
     * Retrieves a single metric by name.
     * @param name - The name of the metric.
     * @returns The metric or undefined if not found.
     */
    getMetric(name: string): Metric | undefined;
    /**
     * Retrieves a single metric value in Prometheus format.
     * @param name - The name of the metric.
     * @returns A promise resolved with the metric value as a string.
     */
    getMetricAsString(name: string): Promise<string>;
    /**
     * Retrieves a single metric value in JSON format.
     * @param name - The name of the metric.
     * @returns A promise resolved with the metric object or undefined if not found.
     */
    getMetricAsJSON(name: string): Promise<MetricObjectWithValues<MetricValue<string>> | undefined>;
    /** Placeholder for starting the metrics service. */
    start(): Promise<void>;
    /** Placeholder for stopping the metrics service. */
    stop(): Promise<void>;
    /** Clears all metrics from the registry. */
    close(): Promise<void>;
}
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