metrics-client-whats-the-trouble.ts

import { ClientConfig } from '../Core/types';
import Http from '../utils/Http';
import Url from '../utils/Url';
import { ResourceResult, AutofiServices } from './types';
import Resource from './AbstractResource';

export interface MetricOpts extends ClientConfig {
	autofiService: string;
	metadata: any;
	processInterval: number;
}

interface TimeEvent {
	readonly key: string;
	readonly duration: number;
	readonly metadata: object;
}

export default class Metric extends Resource {
	public metadata: any;
	private autofiService: AutofiServices | string;
	private processing = false;
	private processInterval: number;
	private queue: TimeEvent[] = [];
	private statsMap: Map<string, number> = new Map();

	public constructor(opts: MetricOpts) {
		super('metric');

		this.autofiService = opts.autofiService;
		this.baseUri = opts.uris.METRIC_SERVICE_URI;
		this.metadata = opts.metadata;
		this.processInterval = opts.processInterval || 5000;
	}

	private formatKey(key: string): string {
		return `${this.autofiService}:${key}`;
	}

	private initializeQueue(): void {
		setInterval(this.processQueue.bind(this), this.processInterval);
		this.processing = true;
	}

	private processQueue(): void {
		if (this.queue.length === 0) {
			return;
		}

		Http.fetch(Url.stringify(this.baseUri, `/metrics/stats`), {
			method: 'POST',
			body: JSON.stringify({ data: this.queue }),
			headers: { 'Content-Type': 'application/json' },
		});

		this.queue = [];
	}

	/**
	 * Mark the start of a performance timer
	 *
	 * @param {string} key <scope:event> e.g., scraper:ui-handoff
	 * @returns {void}
	 * @memberof Metric
	 */
	public mark(key: string): void {
		this.statsMap.set(this.formatKey(key), Date.now());
	}

	/**
	 * Time a performance event
	 *
	 * @param {string} key <scope:event> e.g., scraper:ui-handoff
	 * @param {object?} metadata
	 * @returns {void}
	 * @memberof Metric
	 */
	public timing(key: string, metadata?: object): void {
		const now = Date.now();
		const formattedKey = this.formatKey(key);
		const startTime = this.statsMap.get(formattedKey);
		if (!startTime) {
			return;
		}
		const duration = now - startTime;

		if (!this.processing) {
			this.initializeQueue();
		}

		const combinedMetadata = { ...this.metadata, ...metadata };
		this.queue.push({ key: formattedKey, duration, metadata: combinedMetadata });
		this.statsMap.delete(formattedKey);
	}

	/**
	 * Create a heartbeat
	 *
	 * @param {AutofiServices} [key]
	 * @param {any} data
	 * @returns {Promise<ResourceResult>}
	 * @memberof Metric
	 */
	public async heartbeat(
		key: AutofiServices | string = AutofiServices.None,
		data?: any
	): Promise<ResourceResult> {
		return Http.fetch(Url.stringify(this.baseUri, `/metrics/heartbeat`), {
			method: 'POST',
			body: JSON.stringify({
				data,
				key,
			}),
			headers: {
				'Content-Type': 'application/json',
			},
		});
	}

	/**
	 * Returns metric data
	 *
	 * @param {any} data
	 * @returns {Promise<ResourceResult>}
	 * @memberof Metric
	 */
	public async data(): Promise<ResourceResult> {
		return Http.fetch(Url.stringify(this.baseUri, `/metrics/data`));
	}
}
		
/*************************************************************************/
// express endpoint
const Metric = require('...');
...
app.get('/', () => {
  metricsClient = Metric.create({	
		autofiService: 'Service Name',
		... other config options
	});
};