使用 Node.js 的 Async Hooks 模块追踪异步资源

const asyncHooks = require('async_hooks');
const fs = require('fs');
const asyncId = () => asyncHooks.executionAsyncId();
const triggerAsyncId = () => asyncHooks.triggerAsyncId();

console.log(`Global asyncId: ${asyncHooks.executionAsyncId()}, Global triggerAsyncId: ${triggerAsyncId()}`);

fs.open('hello.txt', (err, res) => {
  console.log(`fs.open asyncId: ${asyncId()}, fs.open triggerAsyncId: ${triggerAsyncId()}`);
});

Global asyncId: 1, Global triggerAsyncId: 0
fs.open asyncId: 5, fs.open triggerAsyncId: 1

Promise.resolve().then(() => {
  // Promise asyncId: 0. Promise triggerAsyncId: 0
  console.log(`Promise asyncId: ${asyncId()}. Promise triggerAsyncId: ${triggerAsyncId()}`);
})

const hooks = asyncHooks.createHook({});
hooks.enable();

Promise.resolve().then(() => {
  // Promise asyncId: 7. Promise triggerAsyncId: 6
  console.log(`Promise asyncId: ${asyncId()}. Promise triggerAsyncId: ${triggerAsyncId()}`);
})

/**
 * Called when a class is constructed that has the possibility to emit an asynchronous event.
 * @param asyncId a unique ID for the async resource
 * @param type the type of the async resource
 * @param triggerAsyncId the unique ID of the async resource in whose execution context this async resource was created
 * @param resource reference to the resource representing the async operation, needs to be released during destroy
 */
init?(asyncId: number, type: string, triggerAsyncId: number, resource: object): void;

/**
 * When an asynchronous operation is initiated or completes a callback is called to notify the user.
 * The before callback is called just before said callback is executed.
 * @param asyncId the unique identifier assigned to the resource about to execute the callback.
 */
before?(asyncId: number): void;

/**
 * Called immediately after the callback specified in before is completed.
 * @param asyncId the unique identifier assigned to the resource which has executed the callback.
 */
after?(asyncId: number): void;

/**
 * Called after the resource corresponding to asyncId is destroyed
 * @param asyncId a unique ID for the async resource
 */
destroy?(asyncId: number): void;

/**
  * Called when a promise has resolve() called. This may not be in the same execution id
  * as the promise itself.
  * @param asyncId the unique id for the promise that was resolve()d.
  */
promiseResolve?(asyncId: number): void;

const hooks = asyncHooks.createHook({
  promiseResolve(asyncId) {
    syncLog('promiseResolve: ', asyncId);
  }
});
new Promise((resolve) => resolve(true)).then((a) => {});

// 输出结果
promiseResolve:  2
promiseResolve:  3

const syncLog = (...args) => fs.writeFileSync('log.txt', `${util.format(...args)}\n`, { flag: 'a' });
const hooks = asyncHooks.createHook({
  init(asyncId, type, triggerAsyncId, resource) {
    syncLog('init: ', asyncId, type, triggerAsyncId)
  }
});
hooks.enable();

fs.open('hello.txt', (err, res) => {
  syncLog(`fs.open asyncId: ${asyncId()}, fs.open triggerAsyncId: ${triggerAsyncId()}`);
});

init:  2 FSREQCALLBACK 1
fs.open asyncId: 2, fs.open triggerAsyncId: 1

const { AsyncLocalStorage } = require('async_hooks');
const asyncLocalStorage = new AsyncLocalStorage();
asyncLocalStorage.run({ traceId: 1 }, test1);
async function test1() {
  setTimeout(() => test2(), 2000);
}
async function test2() {
  console.log(asyncLocalStorage.getStore().traceId);
}

const http = require('http');
const { AsyncLocalStorage } = require('async_hooks');
const asyncLocalStorage = new AsyncLocalStorage();
function logWithId(msg) {
  const id = asyncLocalStorage.getStore();
  console.log(`${id !== undefined ? id : '-'}:`, msg);
}
let idSeq = 0;
http.createServer((req, res) => {
  asyncLocalStorage.run(idSeq++, () => {
    logWithId('start');
    setImmediate(() => {
      logWithId('processing...');
      setTimeout(() => {
        logWithId('finish');
        res.end();
      }, 2000)
    });
  });
}).listen(8080);