Exports

import http from 'node:http';
import { AsyncLocalStorage } from 'node: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');
// Imagine any chain of async operations here
setImmediate(() => {
logWithId('finish');
res.end();
});
});
}).listen(8080);

http.get('http://localhost:8080');
http.get('http://localhost:8080');
// Prints:
//   0: start
//   0: finish
//   1: start
//   1: finish

import { AsyncResource, executionAsyncId } from 'node:async_hooks';

// AsyncResource() is meant to be extended. Instantiating a
// new AsyncResource() also triggers init. If triggerAsyncId is omitted then
// async_hook.executionAsyncId() is used.
const asyncResource = new AsyncResource(
type, { triggerAsyncId: executionAsyncId(), requireManualDestroy: false },
);

// Run a function in the execution context of the resource. This will
// * establish the context of the resource
// * trigger the AsyncHooks before callbacks
// * call the provided function `fn` with the supplied arguments
// * trigger the AsyncHooks after callbacks
// * restore the original execution context
asyncResource.runInAsyncScope(fn, thisArg, ...args);

// Call AsyncHooks destroy callbacks.
asyncResource.emitDestroy();

// Return the unique ID assigned to the AsyncResource instance.
asyncResource.asyncId();

// Return the trigger ID for the AsyncResource instance.
asyncResource.triggerAsyncId();

import { createHook } from 'node:async_hooks';

const asyncHook = createHook({
init(asyncId, type, triggerAsyncId, resource) { },
destroy(asyncId) { },
});

class MyAsyncCallbacks {
init(asyncId, type, triggerAsyncId, resource) { }
destroy(asyncId) {}
}

class MyAddedCallbacks extends MyAsyncCallbacks {
before(asyncId) { }
after(asyncId) { }
}

const asyncHook = async_hooks.createHook(new MyAddedCallbacks());

import { executionAsyncId } from 'node:async_hooks';
import fs from 'node:fs';

console.log(executionAsyncId());  // 1 - bootstrap
const path = '.';
fs.open(path, 'r', (err, fd) => {
console.log(executionAsyncId());  // 6 - open()
});

const server = net.createServer((conn) => {
// Returns the ID of the server, not of the new connection, because the
// callback runs in the execution scope of the server's MakeCallback().
async_hooks.executionAsyncId();

}).listen(port, () => {
// Returns the ID of a TickObject (process.nextTick()) because all
// callbacks passed to .listen() are wrapped in a nextTick().
async_hooks.executionAsyncId();
});

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
});

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 server = net.createServer((conn) => {
// The resource that caused (or triggered) this callback to be called
// was that of the new connection. Thus the return value of triggerAsyncId()
// is the asyncId of "conn".
async_hooks.triggerAsyncId();

}).listen(port, () => {
// Even though all callbacks passed to .listen() are wrapped in a nextTick()
// the callback itself exists because the call to the server's .listen()
// was made. So the return value would be the ID of the server.
async_hooks.triggerAsyncId();
});