async_hooks.executionAsyncResource()

• 返回: <Object> 代表当前执行的资源。 用于在资源中存储数据。

executionAsyncResource() 返回的资源对象通常是带有未记录 API 的内部 Node.js 句柄对象。 在对象上使用任何函数或属性都可能使您的应用程序崩溃，应该避免。

在顶层执行上下文中使用 executionAsyncResource() 将返回空的对象，因为没有要使用的句柄或请求对象，但是有一个代表顶层的对象可能会有所帮助。

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
});

这可用于实现连续本地存储，无需使用跟踪 Map 来存储元数据：

import { createServer } from 'node:http';
import {
  executionAsyncId,
  executionAsyncResource,
  createHook
} from 'async_hooks';
const sym = Symbol('state'); // 避免污染的私有符号

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'); // 避免污染的私有符号

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);

• Returns: <Object> The resource representing the current execution. Useful to store data within the resource.

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.

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
});

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 '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);