How Can I Achieve Truly Non-Blocking Code in Node.js?

Correct Way to Achieve Non-Blocking Code in Node.js

In asynchronous programming, non-blocking functions allow other code to execute concurrently without waiting for their completion. However, simply wrapping code in a Promise, as in the example below, does not make it truly non-blocking.

function longRunningFunc(val, mod) {
    return new Promise((resolve, reject) => {
        sum = 0;
        for (var i = 0; i < 100000; i++) {
            for (var j = 0; j < val; j++) {
                sum += i + j % mod
            }
        }
        resolve(sum)
    })
}

Despite wrapping the code in a Promise, the program waits before printing, indicating that the code is blocking.

Understanding Non-Blocking Code

In Node.js, plain JavaScript code is inherently blocking and runs in a single thread. No amount of wrapping in Promises or asynchronous APIs can make it non-blocking. To achieve non-blocking behavior, one must utilize techniques that shift code execution to external threads or adopt experimental Node.js APIs for threads.

Achieving Non-Blocking Code

Here are some ways to create genuine non-blocking code in Node.js:

• Child Processes: Run code in a separate child process and access results asynchronously.
• Worker Threads (Node.js v11 ): Utilize the experimental Worker Threads feature to create separate worker threads parallel to the main thread.
• Native Code Add-ons: Write native code extensions using Node.js's add-on mechanism and employ libuv threads or operating system-level threads.
• Asynchronous APIs: Build upon existing asynchronous APIs without prolonging code execution in the main thread.

By implementing non-blocking techniques, Node.js applications can effectively handle long-running operations without hindering other code executions, resulting in enhanced responsiveness and concurrency.

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