Implementation of async NodeJS request tracing

requestTracker.js

/**
 * Robust implementation of request tracing. 
 * Just add getRequestTracker().withRequest(req) at the first instance of incoming http request and
 * it will persist request details during the whole request processing chain, async or not.
 * 
 * Similar how AWS X-Ray works, or how NextJS 13+ cookies() method were implemented.
 * 
 * Licensed under: MIT License
 *
 * Copyright (c) 2024 Ruslan Gainutdinov
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
const { AsyncLocalStorage } = require("async_hooks");
const { randomUUID } = require("crypto");

const asyncLocalStorage = new AsyncLocalStorage();

class RequestTracker {
  constructor() {}

  toString() {
    return " " + getRequest().requestId;
  }

  /**
   * Enters async chain with specific request.
   *
   * @param {import('http').IncomingMessage} req
   * @param {string|undefined|null} [requestId]
   **/
  withRequest(req, requestId) {
    return asyncLocalStorage.enterWith({
      requestId: requestId ?? randomUUID(),
      url: req.url
    });
  }

  /**
   * Returns current request details, if any.
   *
   * @returns {{requestId: string, url: string}|undefined}
   */
  getRequest() {
    const v = {
      requestId: asyncLocalStorage.getStore()?.requestId,
      url: asyncLocalStorage.getStore()?.url
    };
    if (v.url) {
      return v;
    } else {
      return undefined;
    }
  }

  [Symbol.toPrimitive](hint) {
    if (hint === "string") {
      return " " + this.getRequest().requestId;
    }
    return null;
  }
}

if (
  !global.__requestTrace &&
  (process.env.NODE_ENV === "production" || process.env.LOG_REQUEST_TRACE === "1")
) {
  // eslint-disable-next-line no-console
  console.info("Installing async request tracker...");
  global.__requestTrace = new RequestTracker();
}

/**
 * @returns {RequestTracker|undefined}
 */
const getRequestTracker = () => {
  return global.__requestTrace;
};

module.exports = {
  getRequestTracker
};