성능 최적화를 위해 Node.js의 비동기 후크 활용Korean version of this document is available
Node.js で非同期フックを活用してパフォーマンスを最適化するJapanese version of this document is available
利用 Node.js 中的异步挂钩进行性能优化Chinese Simplified version of this document is available
Async functions are a powerful way to perform operations asynchronously. Node.js provides several ways to work with async functions, including the async/await keywords and the Promise API.
Async functions are non-blocking, meaning they don't block the main thread. This is important because blocking the main thread can cause the entire program to pause. Async functions allow you to write code that is more responsive and can handle more concurrent requests.
There are a few things to keep in mind when working with async functions. First, async functions return a Promise. A Promise is an object that represents the result of an async operation. Promises can be in one of three states: pending, fulfilled, or rejected.
Second, async functions can throw errors just like regular functions. It's important to catch these errors, or the program will crash.
Third, async functions can be used with the await keyword. The await keyword can only be used inside an async function. It causes the program to pause until the async operation is complete.
Async functions are a great way to improve the performance of Node.js programs. In this article, we'll discuss how to use async functions and some of the benefits they offer.
Async hooks are a way to track async operations. They can be used to instrument code, collect data, and improve performance.
Async hooks were introduced in Node.js 8. As of Node.js 10, there are seven different async hooks:
async_hooks.createHook
: Used to create a new async hook instance.async_hooks.executionAsyncId
: Used to get the async ID of the current execution context.async_hooks.triggerAsyncId
: Used to get the async ID of the trigger of the current async operation.async_hooks.currentId
: Used to get the async ID of the current async operation.async_hooks.emitInit
: Used to emit an 'init' event.async_hooks.emitBefore
: Used to emit a 'before' event.async_hooks.emitAfter
: Used to emit an 'after' event.async_hooks.emitDestroy
: Used to emit a 'destroy' event.Async hooks can be used to track the life cycle of an async operation. The 'init', 'before', 'after', and 'destroy' events are emitted at different points in the life cycle.
The 'init' event is emitted when an async operation is created. The 'before' event is emitted before the async operation is executed. The 'after' event is emitted after the async operation is executed. The 'destroy' event is emitted when the async operation is destroyed.
Async hooks can be used to collect data about async operations. This data can be used to improve performance.
Async hooks can be used in two ways: with callbacks or with Promises.
Using callbacks is the most common way to use async hooks. To use async hooks with callbacks, you must first create a hook instance. This is done with the async_hooks.createHook
function.
const asyncHooks = require('async_hooks');
const hook = asyncHooks.createHook({
init,
before,
after,
destroy
});
The createHook
function takes an object with four properties: init
, before
, after
, and destroy
. These properties are functions that are called when the corresponding event is emitted.
The init
function is called when the 'init' event is emitted. The before
function is called when the 'before' event is emitted. The after
function is called when the 'after' event is emitted. The destroy
function is called when the 'destroy' event is emitted.
The functions are passed an asyncId
argument. This argument is the async ID of the async operation.
function init(asyncId) {
// do something
}
function before(asyncId) {
// do something
}
function after(asyncId) {
// do something
}
function destroy(asyncId) {
// do something
}
After the hook instance is created, you must enable it. This is done with the enable
function.
hook.enable();
Once the hook is enabled, it will start tracking async operations. The functions that were passed to the createHook
function will be called at the appropriate times.
To disable the hook, you can use the disable
function.
hook.disable();
Async hooks can also be used with Promises. To use async hooks with Promises, you must first create a hook instance. This is done with the async_hooks.createHook
function.
const asyncHooks = require('async_hooks');
const hook = asyncHooks.createHook({
init,
before,
after,
destroy
});
The createHook
function takes an object with four properties: init
, before
, after
, and destroy
. These properties are functions that are called when the corresponding event is emitted.
The init
function is called when the 'init' event is emitted. The before
function is called when the 'before' event is emitted. The after
function is called when the 'after' event is emitted. The destroy
function is called when the 'destroy' event is emitted.
The functions are passed an asyncId
argument. This argument is the async ID of the async operation.
function init(asyncId) {
// do something
}
function before(asyncId) {
// do something
}
function after(asyncId) {
// do something
}
function destroy(asyncId) {
// do something
}
After the hook instance is created, you must enable it. This is done with the enable
function.
hook.enable();
Once the hook is enabled, it will start tracking async operations. The functions that were passed to the createHook
function will be called at the appropriate times.
To disable the hook, you can use the disable
function.
hook.disable();
Async hooks can be used to collect data about async operations. This data can be used to improve performance.
Async hooks can be used to collect data about async operations. This data can be used to improve performance.
Async hooks can help you understand what's happening in your program. They can be used to find bottlenecks and optimize code.
Async hooks can also be used to instrument code. Instrumentation is the process of adding code to a program to collect data. Async hooks can be used to instrument code and collect data about async operations. This data can be used to improve performance.
Instrumentation can be used to collect data about async operations. This data can be used to improve performance.
Async hooks are a powerful way to collect data about async operations. This data can be used to improve performance. Async hooks can be used to instrument code, collect data, and improve performance.