async_hooks.executionAsyncResource()

• 返回：<Object> 表示当前执行的资源。可用于在资源中存储数据。

executionAsyncResource() 返回的资源对象大多是内部的 Node.js 句柄对象，具有未记录的 API。在这些对象上使用任何函数或属性很可能会导致应用崩溃，应避免这样做。

【Resource objects returned by executionAsyncResource() are most often internal Node.js handle objects with undocumented APIs. Using any functions or properties on the object is likely to crash your application and should be avoided.】

在顶层执行上下文中使用 executionAsyncResource() 将返回一个空对象，因为没有可用的句柄或请求对象，但拥有一个表示顶层的对象可能是有用的。

【Using executionAsyncResource() in the top-level execution context will return an empty object as there is no handle or request object to use, but having an object representing the top-level can be helpful.】

import { open } from 'node:fs';
import { executionAsyncId, executionAsyncResource } from 'node:async_hooks';

console.log(executionAsyncId(), executionAsyncResource());  // 1 {}
open(new URL(import.meta.url), 'r', (err, fd) => {
  console.log(executionAsyncId(), executionAsyncResource());  // 7 FSReqWrap
});const { open } = require('node:fs');
const { executionAsyncId, executionAsyncResource } = require('node:async_hooks');

console.log(executionAsyncId(), executionAsyncResource());  // 1 {}
open(__filename, 'r', (err, fd) => {
  console.log(executionAsyncId(), executionAsyncResource());  // 7 FSReqWrap
});拷贝

这可以用来实现连续本地存储，而无需使用跟踪 Map 来存储元数据：

【This can be used to implement continuation local storage without the use of a tracking Map to store the metadata:】

import { createServer } from 'node:http';
import {
  executionAsyncId,
  executionAsyncResource,
  createHook,
} from 'node:async_hooks';
const sym = Symbol('state'); // Private symbol to avoid pollution

createHook({
  init(asyncId, type, triggerAsyncId, resource) {
    const cr = executionAsyncResource();
    if (cr) {
      resource[sym] = cr[sym];
    }
  },
}).enable();

const server = createServer((req, res) => {
  executionAsyncResource()[sym] = { state: req.url };
  setTimeout(function() {
    res.end(JSON.stringify(executionAsyncResource()[sym]));
  }, 100);
}).listen(3000);const { createServer } = require('node:http');
const {
  executionAsyncId,
  executionAsyncResource,
  createHook,
} = require('node:async_hooks');
const sym = Symbol('state'); // Private symbol to avoid pollution

createHook({
  init(asyncId, type, triggerAsyncId, resource) {
    const cr = executionAsyncResource();
    if (cr) {
      resource[sym] = cr[sym];
    }
  },
}).enable();

const server = createServer((req, res) => {
  executionAsyncResource()[sym] = { state: req.url };
  setTimeout(function() {
    res.end(JSON.stringify(executionAsyncResource()[sym]));
  }, 100);
}).listen(3000);拷贝