@dishuostec/llrt-types
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Type definitions for LLRT, Low Latency Runtime
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TypeScript
/**
* We strongly discourage the use of the `async_hooks` API.
* Other APIs that can cover most of its use cases include:
*
* * [`AsyncLocalStorage`](https://nodejs.org/docs/latest-v22.x/api/async_context.html#class-asynclocalstorage) tracks async context
* * [`process.getActiveResourcesInfo()`](https://nodejs.org/docs/latest-v22.x/api/process.html#processgetactiveresourcesinfo) tracks active resources
*
* The `async_hooks` module provides an API to track asynchronous resources.
* It can be accessed using:
*
* ```js
* import async_hooks from 'async_hooks';
* ```
* @experimental
* @see [source](https://github.com/nodejs/node/blob/v22.x/lib/async_hooks.js)
*/
declare module "async_hooks" {
/**
* ```js
* import { executionAsyncId } from 'async_hooks';
* import fs from 'fs';
*
* console.log(executionAsyncId()); // 1 - bootstrap
* const path = '.';
* fs.open(path, 'r', (err, fd) => {
* console.log(executionAsyncId()); // 6 - open()
* });
* ```
*
* The ID returned from `executionAsyncId()` is related to execution timing, not
* causality (which is covered by `triggerAsyncId()`):
*
* ```js
* 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();
* });
* ```
*
* Promise contexts may not get precise `executionAsyncIds` by default.
* See the section on [promise execution tracking](https://nodejs.org/docs/latest-v22.x/api/async_hooks.html#promise-execution-tracking).
* @return The `asyncId` of the current execution context. Useful to track when something calls.
*/
function executionAsyncId(): number;
/**
* Resource objects returned by `executionAsyncResource()` are most often internal
* LLRT 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.
*
* ```js
* import { open } from 'fs';
* import { executionAsyncId, executionAsyncResource } from 'async_hooks';
*
* console.log(executionAsyncId(), executionAsyncResource()); // 1 {}
* open(new URL(import.meta.url), '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:
*
* ```js
* import { createServer } from '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);
* ```
* @return The resource representing the current execution. Useful to store data within the resource.
*/
function executionAsyncResource(): object;
/**
* ```js
* 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();
* });
* ```
*
* Promise contexts may not get valid `triggerAsyncId`s by default. See
* the section on [promise execution tracking](https://nodejs.org/docs/latest-v22.x/api/async_hooks.html#promise-execution-tracking).
* @return The ID of the resource responsible for calling the callback that is currently being executed.
*/
function triggerAsyncId(): number;
interface HookCallbacks {
/**
* 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
*/
init?(asyncId: number, type: string, triggerAsyncId: number): 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.
*
* If an uncaught exception occurs during execution of the callback, then `after` will run after the `'uncaughtException'` event is emitted or a `domain`'s handler runs.
* @param asyncId the unique identifier assigned to the resource which has executed the callback.
*/
after?(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;
/**
* Called after the resource corresponding to asyncId is destroyed
* @param asyncId a unique ID for the async resource
*/
destroy?(asyncId: number): void;
}
interface AsyncHook {
/**
* Enable the callbacks for a given AsyncHook instance. If no callbacks are provided enabling is a noop.
*/
enable(): this;
/**
* Disable the callbacks for a given AsyncHook instance from the global pool of AsyncHook callbacks to be executed. Once a hook has been disabled it will not be called again until enabled.
*/
disable(): this;
}
/**
* Registers functions to be called for different lifetime events of each async
* operation.
*
* The callbacks `init()`/`before()`/`after()`/`destroy()` are called for the
* respective asynchronous event during a resource's lifetime.
*
* All callbacks are optional. For example, if only resource cleanup needs to
* be tracked, then only the `destroy` callback needs to be passed. The
* specifics of all functions that can be passed to `callbacks` is in the `Hook Callbacks` section.
*
* ```js
* import { createHook } from 'async_hooks';
*
* const asyncHook = createHook({
* init(asyncId, type, triggerAsyncId, resource) { },
* destroy(asyncId) { },
* });
* ```
*
* The callbacks will be inherited via the prototype chain:
*
* ```js
* class MyAsyncCallbacks {
* init(asyncId, type, triggerAsyncId, resource) { }
* destroy(asyncId) {}
* }
*
* class MyAddedCallbacks extends MyAsyncCallbacks {
* before(asyncId) { }
* after(asyncId) { }
* }
*
* const asyncHook = async_hooks.createHook(new MyAddedCallbacks());
* ```
*
* Because promises are asynchronous resources whose lifecycle is tracked
* via the async hooks mechanism, the `init()`, `before()`, `after()`, and`destroy()` callbacks _must not_ be async functions that return promises.
* @param callbacks The `Hook Callbacks` to register
* @return Instance used for disabling and enabling hooks
*/
function createHook(callbacks: HookCallbacks): AsyncHook;
}
declare module "async_hooks" {
export * from "async_hooks";
}