WebAssembly (WASM) for High Performance Apps · 강의

WASM을 활용한 비동기 작업

프로미스와 async/await를 사용하여 메인 스레드를 차단하지 않고 WASM에서 장시간 실행되는 작업을 처리하는 비동기 패턴을 구현합니다.

WASM을 활용한 비동기 작업은(는) CoddyKit의 무료 WebAssembly (WASM) for High Performance Apps 강의입니다. 이것은 4개 중 1번째 강의입니다. 아래에서 전체 강의를 무료로 읽을 수 있으며, 내장 코드 에디터와 24/7 AI 튜터와 함께 브라우저에서 직접 실습할 수 있습니다. 이 강의는 WebAssembly (WASM) for High Performance Apps 학습 경로의 일부이며, 진행 상황이 웹과 CoddyKit 앱에 동기화됩니다. WebAssembly (WASM) for High Performance Apps 강의에는 총 4개의 강의가 포함되어 있습니다.

이 강의의 일부는 아직 번역되지 않았으며 영어로 표시됩니다.

Why Asynchronous WASM?

When a WebAssembly module performs a complex calculation or a long task, it can freeze your web page. This is because JavaScript is single-threaded, and most direct WASM calls are synchronous.

Asynchronous WASM patterns allow these tasks to run without completely blocking the main browser thread, keeping your UI responsive.

WASM's Synchronous Nature

When JavaScript calls an exported WASM function, that function executes entirely before JavaScript regains control. If the WASM function takes a long time, the browser's main thread will be blocked.

This means no UI updates, no user input processing, making the page appear frozen. True parallel execution for WASM often involves Web Workers, which is covered in another lesson.

Strategy: Breaking into Chunks

To prevent blocking the main thread, we can break a long-running WASM task into smaller, manageable chunks. Instead of one huge, blocking WASM call, we make many small ones.

Between each small WASM call, JavaScript can yield control back to the browser's event loop. This allows the UI to update and remain responsive.

WASM Function for a Chunk

Here's a Rust function that represents one "chunk" of work. It takes a starting value and performs a small number of calculations. In a real application, this could process a part of an image or a segment of data.

pub extern "C" fn process_chunk(start_val: u32, iterations: u32) -> u32 {
    let mut sum = start_val;
    for i in 0..iterations {
        sum = sum.wrapping_add(i); // Simulate work, prevent overflow
    }
    sum
}

Promises in JavaScript

To handle asynchronous operations, JavaScript uses Promises. A Promise represents the eventual completion (or failure) of an asynchronous operation and its resulting value.

Pending: Initial state, neither fulfilled nor rejected.
Fulfilled: Operation completed successfully.
Rejected: Operation failed.

We use .then() for success and .catch() for errors.

Simplifying with async/await

async/await is syntactic sugar built on Promises, making asynchronous code look and behave more like synchronous code, improving readability. It's built on Promises.

An async function always returns a Promise.
The await keyword can only be used inside an async function. It pauses the execution until the Promise settles, allowing other tasks to run.

This is crucial for orchestrating our WASM chunks.

Making WASM Calls Yield

We can create a JavaScript utility function that wraps a synchronous WASM call in a Promise. By using setTimeout(..., 0), we tell the browser to execute the WASM call after the current event loop cycle finishes.

This effectively "yields" control back to the browser, allowing it to update the UI before the next WASM chunk runs.

function callWasmAsync(wasmExports, funcName, ...args) {
  return new Promise(resolve => {
    setTimeout(() => {
      const result = wasmExports[funcName](...args);
      resolve(result);
    }, 0); // Yield control to the event loop
  });
}

Full Async WASM Example

Here's a complete, runnable example demonstrating how to manage a long-running WASM task asynchronously using chunking and JavaScript's async/await.

Notice how `setTimeout(0)` around the WASM call allows the browser to breathe between chunks.

// main.js
// Assume wasm_module.wasm (containing process_chunk) is loaded.
// For this runnable example, we'll simulate the WASM function.

// This simulates our WASM module's process_chunk function
function simulateWasmProcessChunk(start_val, iterations) {
    let sum = start_val;
    for (let i = 0; i < iterations; i++) {
        sum = (sum + i) % 10000; // Simplified calculation
    }
    return sum;
}

// Utility to call a synchronous task asynchronously
function callSyncTaskAsync(taskFunc, ...args) {
  return new Promise(resolve => {
    setTimeout(() => {
      const result = taskFunc(...args);
      resolve(result);
    }, 0); // Yield control to the event loop
  });
}

async function performLongTask() {
  console.log("Starting async task...");
  let currentSum = 0;
  const totalChunks = 5;
  const iterationsPerChunk = 10_000_000; // Simulate heavy work

  for (let i = 0; i < totalChunks; i++) {
    // Call the simulated WASM chunk asynchronously
    currentSum = await callSyncTaskAsync(
      simulateWasmProcessChunk,
      currentSum,
      iterationsPerChunk
    );
    console.log(`Chunk ${i + 1} done. Current sum: ${currentSum}`);
  }
  console.log("Async task finished. Final sum:", currentSum);
  return currentSum;
}

performLongTask();

Handling Errors Asynchronously

Just like any asynchronous operation, you should handle potential errors. If a WASM chunk call fails (e.g., due to invalid input or memory issues), the Promise will reject.

You can use try...catch with async/await or .catch() with Promises to gracefully handle these situations in your JavaScript code.

Async WASM Check

Consider a WebAssembly function heavy_calc() that takes 5 seconds to run. If you call it directly from JavaScript's main thread, what is the primary consequence?

Recap: Async WASM Patterns

We've learned how to handle long-running WASM tasks asynchronously on the main thread without using Web Workers. Key takeaways:

WASM functions are synchronous when called from JavaScript.
Break long tasks into smaller "chunks."
Use JavaScript Promises and async/await to orchestrate these chunks.
Yield control to the browser's event loop (e.g., with setTimeout(0)) between chunk calls to keep the UI responsive.

This pattern is crucial for maintaining a smooth user experience in complex web applications.

자주 묻는 질문

“WASM을 활용한 비동기 작업” 강의는 무료인가요?

네 — “WASM을 활용한 비동기 작업” 전체 내용을 이 웹사이트에서 무료로 읽을 수 있습니다. 인터랙티브하게 실습하려면(내장 코드 에디터와 24/7 AI 튜터), CoddyKit PRO로 업그레이드하면 WebAssembly (WASM) for High Performance Apps 강의 전체를 잠금 해제할 수 있습니다. WebAssembly (WASM) for High Performance Apps 강의에는 총 4개의 강의가 포함되어 있습니다.

“WASM을 활용한 비동기 작업”에서 뭘 배우나요?

프로미스와 async/await를 사용하여 메인 스레드를 차단하지 않고 WASM에서 장시간 실행되는 작업을 처리하는 비동기 패턴을 구현합니다. 브라우저에서 직접 실행하는 실습 코드로 WebAssembly (WASM) for High Performance Apps을(를) 배우며, 24/7 AI 튜터가 강의를 진행하면서 질문에 답변해줍니다.

WebAssembly (WASM) for High Performance Apps을(를) 시작하는 데 경험이 필요한가요?

사전 경험은 필요하지 않습니다. CoddyKit의 WebAssembly (WASM) for High Performance Apps은(는) 초급자부터 고급 학습자까지를 위해 구성되어 있으므로, 여기서 시작하거나 처음부터 시작할 수 있으며 자신의 속도대로 진행할 수 있습니다. 이것은 4개 중 1번째 강의입니다.

“WASM을 활용한 비동기 작업” 강의는 얼마나 걸리나요?

대부분의 CoddyKit 강의는 약 5~10분이 소요됩니다. 각 강의는 간결하고 인터랙티브하여 꾸준한 진행이 가능하며, 웹과 앱에서 중단한 부분부터 바로 시작할 수 있습니다.

이 WebAssembly (WASM) for High Performance Apps 강의에서 코드를 작성하고 실행할 수 있나요?

네. 모든 WebAssembly (WASM) for High Performance Apps 강의에는 내장 코드 에디터가 포함되어 있으므로, 브라우저에서 바로 실제 코드를 작성하고 실행한 후 즉시 AI 피드백을 받을 수 있습니다 — 로컬 설정이 필요 없습니다.

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