@types/node/async_hooks.d.ts

/**
 * The `async_hooks` module provides an API to track asynchronous resources. It
 * can be accessed using:
 *
 * ```js
 * const async_hooks = require('async_hooks');
 * ```
 * @experimental
 * @see [source](https://github.com/nodejs/node/blob/v16.4.2/lib/async_hooks.js)
 */
declare module 'async_hooks' {
    /**
     * ```js
     * const async_hooks = require('async_hooks');
     *
     * console.log(async_hooks.executionAsyncId());  // 1 - bootstrap
     * fs.open(path, 'r', (err, fd) => {
     *   console.log(async_hooks.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`.
     * @since v8.1.0
     * @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
     * 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.
     *
     * ```js
     * const { open } = require('fs');
     * const { executionAsyncId, executionAsyncResource } = require('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:
     *
     * ```js
     * const { createServer } = require('http');
     * const {
     *   executionAsyncId,
     *   executionAsyncResource,
     *   createHook
     * } = require('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);
     * ```
     * @since v13.9.0, v12.17.0
     * @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`.
     * @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
         * @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 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
     * const async_hooks = require('async_hooks');
     *
     * const asyncHook = async_hooks.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.
     * @since v8.1.0
     * @param callbacks The `Hook Callbacks` to register
     * @return Instance used for disabling and enabling hooks
     */
    function createHook(callbacks: HookCallbacks): AsyncHook;
    interface AsyncResourceOptions {
        /**
         * The ID of the execution context that created this async event.
         * @default executionAsyncId()
         */
        triggerAsyncId?: number | undefined;
        /**
         * Disables automatic `emitDestroy` when the object is garbage collected.
         * This usually does not need to be set (even if `emitDestroy` is called
         * manually), unless the resource's `asyncId` is retrieved and the
         * sensitive API's `emitDestroy` is called with it.
         * @default false
         */
        requireManualDestroy?: boolean | undefined;
    }
    /**
     * The class `AsyncResource` is designed to be extended by the embedder's async
     * resources. Using this, users can easily trigger the lifetime events of their
     * own resources.
     *
     * The `init` hook will trigger when an `AsyncResource` is instantiated.
     *
     * The following is an overview of the `AsyncResource` API.
     *
     * ```js
     * const { AsyncResource, executionAsyncId } = require('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();
     * ```
     */
    class AsyncResource {
        /**
         * AsyncResource() is meant to be extended. Instantiating a
         * new AsyncResource() also triggers init. If triggerAsyncId is omitted then
         * async_hook.executionAsyncId() is used.
         * @param type The type of async event.
         * @param triggerAsyncId The ID of the execution context that created
         *   this async event (default: `executionAsyncId()`), or an
         *   AsyncResourceOptions object (since 9.3)
         */
        constructor(type: string, triggerAsyncId?: number | AsyncResourceOptions);
        /**
         * Binds the given function to the current execution context.
         *
         * The returned function will have an `asyncResource` property referencing
         * the `AsyncResource` to which the function is bound.
         * @since v14.8.0, v12.19.0
         * @param fn The function to bind to the current execution context.
         * @param type An optional name to associate with the underlying `AsyncResource`.
         */
        static bind<Func extends (this: ThisArg, ...args: any[]) => any, ThisArg>(
            fn: Func,
            type?: string,
            thisArg?: ThisArg
        ): Func & {
            asyncResource: AsyncResource;
        };
        /**
         * Binds the given function to execute to this `AsyncResource`'s scope.
         *
         * The returned function will have an `asyncResource` property referencing
         * the `AsyncResource` to which the function is bound.
         * @since v14.8.0, v12.19.0
         * @param fn The function to bind to the current `AsyncResource`.
         */
        bind<Func extends (...args: any[]) => any>(
            fn: Func
        ): Func & {
            asyncResource: AsyncResource;
        };
        /**
         * Call the provided function with the provided arguments in the execution context
         * of the async resource. This will establish the context, trigger the AsyncHooks
         * before callbacks, call the function, trigger the AsyncHooks after callbacks, and
         * then restore the original execution context.
         * @since v9.6.0
         * @param fn The function to call in the execution context of this async resource.
         * @param thisArg The receiver to be used for the function call.
         * @param args Optional arguments to pass to the function.
         */
        runInAsyncScope<This, Result>(fn: (this: This, ...args: any[]) => Result, thisArg?: This, ...args: any[]): Result;
        /**
         * Call all `destroy` hooks. This should only ever be called once. An error will
         * be thrown if it is called more than once. This **must** be manually called. If
         * the resource is left to be collected by the GC then the `destroy` hooks will
         * never be called.
         * @return A reference to `asyncResource`.
         */
        emitDestroy(): this;
        /**
         * @return The unique `asyncId` assigned to the resource.
         */
        asyncId(): number;
        /**
         *
         * @return The same `triggerAsyncId` that is passed to the `AsyncResource` constructor.
         */
        triggerAsyncId(): number;
    }
    /**
     * This class creates stores that stay coherent through asynchronous operations.
     *
     * While you can create your own implementation on top of the `async_hooks` module,`AsyncLocalStorage` should be preferred as it is a performant and memory safe
     * implementation that involves significant optimizations that are non-obvious to
     * implement.
     *
     * The following example uses `AsyncLocalStorage` to build a simple logger
     * that assigns IDs to incoming HTTP requests and includes them in messages
     * logged within each request.
     *
     * ```js
     * 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');
     *     // 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
     * //   1: start
     * //   0: finish
     * //   1: finish
     * ```
     *
     * Each instance of `AsyncLocalStorage` maintains an independent storage context.
     * Multiple instances can safely exist simultaneously without risk of interfering
     * with each other data.
     * @since v13.10.0, v12.17.0
     */
    class AsyncLocalStorage<T> {
        /**
         * Disables the instance of `AsyncLocalStorage`. All subsequent calls
         * to `asyncLocalStorage.getStore()` will return `undefined` until`asyncLocalStorage.run()` or `asyncLocalStorage.enterWith()` is called again.
         *
         * When calling `asyncLocalStorage.disable()`, all current contexts linked to the
         * instance will be exited.
         *
         * Calling `asyncLocalStorage.disable()` is required before the`asyncLocalStorage` can be garbage collected. This does not apply to stores
         * provided by the `asyncLocalStorage`, as those objects are garbage collected
         * along with the corresponding async resources.
         *
         * Use this method when the `asyncLocalStorage` is not in use anymore
         * in the current process.
         * @since v13.10.0, v12.17.0
         * @experimental
         */
        disable(): void;
        /**
         * Returns the current store.
         * If called outside of an asynchronous context initialized by
         * calling `asyncLocalStorage.run()` or `asyncLocalStorage.enterWith()`, it
         * returns `undefined`.
         * @since v13.10.0, v12.17.0
         */
        getStore(): T | undefined;
        /**
         * Runs a function synchronously within a context and returns its
         * return value. The store is not accessible outside of the callback function or
         * the asynchronous operations created within the callback.
         *
         * The optional `args` are passed to the callback function.
         *
         * If the callback function throws an error, the error is thrown by `run()` too.
         * The stacktrace is not impacted by this call and the context is exited.
         *
         * Example:
         *
         * ```js
         * const store = { id: 2 };
         * try {
         *   asyncLocalStorage.run(store, () => {
         *     asyncLocalStorage.getStore(); // Returns the store object
         *     throw new Error();
         *   });
         * } catch (e) {
         *   asyncLocalStorage.getStore(); // Returns undefined
         *   // The error will be caught here
         * }
         * ```
         * @since v13.10.0, v12.17.0
         */
        run<R, TArgs extends any[]>(store: T, callback: (...args: TArgs) => R, ...args: TArgs): R;
        /**
         * Runs a function synchronously outside of a context and returns its
         * return value. The store is not accessible within the callback function or
         * the asynchronous operations created within the callback. Any `getStore()`call done within the callback function will always return `undefined`.
         *
         * The optional `args` are passed to the callback function.
         *
         * If the callback function throws an error, the error is thrown by `exit()` too.
         * The stacktrace is not impacted by this call and the context is re-entered.
         *
         * Example:
         *
         * ```js
         * // Within a call to run
         * try {
         *   asyncLocalStorage.getStore(); // Returns the store object or value
         *   asyncLocalStorage.exit(() => {
         *     asyncLocalStorage.getStore(); // Returns undefined
         *     throw new Error();
         *   });
         * } catch (e) {
         *   asyncLocalStorage.getStore(); // Returns the same object or value
         *   // The error will be caught here
         * }
         * ```
         * @since v13.10.0, v12.17.0
         * @experimental
         */
        exit<R, TArgs extends any[]>(callback: (...args: TArgs) => R, ...args: TArgs): R;
        /**
         * Transitions into the context for the remainder of the current
         * synchronous execution and then persists the store through any following
         * asynchronous calls.
         *
         * Example:
         *
         * ```js
         * const store = { id: 1 };
         * // Replaces previous store with the given store object
         * asyncLocalStorage.enterWith(store);
         * asyncLocalStorage.getStore(); // Returns the store object
         * someAsyncOperation(() => {
         *   asyncLocalStorage.getStore(); // Returns the same object
         * });
         * ```
         *
         * This transition will continue for the _entire_ synchronous execution.
         * This means that if, for example, the context is entered within an event
         * handler subsequent event handlers will also run within that context unless
         * specifically bound to another context with an `AsyncResource`. That is why`run()` should be preferred over `enterWith()` unless there are strong reasons
         * to use the latter method.
         *
         * ```js
         * const store = { id: 1 };
         *
         * emitter.on('my-event', () => {
         *   asyncLocalStorage.enterWith(store);
         * });
         * emitter.on('my-event', () => {
         *   asyncLocalStorage.getStore(); // Returns the same object
         * });
         *
         * asyncLocalStorage.getStore(); // Returns undefined
         * emitter.emit('my-event');
         * asyncLocalStorage.getStore(); // Returns the same object
         * ```
         * @since v13.11.0, v12.17.0
         * @experimental
         */
        enterWith(store: T): void;
    }
}
declare module 'node:async_hooks' {
    export * from 'async_hooks';
}