Book Image

JavaScript Concurrency

By : Adam Boduch
Book Image

JavaScript Concurrency

By: Adam Boduch

Overview of this book

Concurrent programming may sound abstract and complex, but it helps to deliver a better user experience. With single threaded JavaScript, applications lack dynamism. This means that when JavaScript code is running, nothing else can happen. The DOM can’t update, which means the UI freezes. In a world where users expect speed and responsiveness – in all senses of the word – this is something no developer can afford. Fortunately, JavaScript has evolved to adopt concurrent capabilities – one of the reasons why it is still at the forefront of modern web development. This book helps you dive into concurrent JavaScript, and demonstrates how to apply its core principles and key techniques and tools to a range of complex development challenges. Built around the three core principles of concurrency – parallelism, synchronization, and conservation – you’ll learn everything you need to unlock a more efficient and dynamic JavaScript, to lay the foundations of even better user experiences. Throughout the book you’ll learn how to put these principles into action by using a range of development approaches. Covering everything from JavaScript promises, web workers, generators and functional programming techniques, everything you learn will have a real impact on the performance of your applications. You’ll also learn how to move between client and server, for a more frictionless and fully realized approach to development. With further guidance on concurrent programming with Node.js, JavaScript Concurrency is committed to making you a better web developer. The best developers know that great design is about more than the UI – with concurrency, you can be confident every your project will be expertly designed to guarantee its dynamism and power.
Table of Contents (17 chapters)
JavaScript Concurrency
About the Author
About the Reviewer

Worker pools

The final section of this chapter covers the concept of worker pools. In the preceding section on Parallel.js, we ran up against an issue where workers were frequently created and terminated. This is a lot of overhead. If we know the level of concurrency we're capable of operating at, then why not allocate a statically-sized pool of workers that can take on work?

The first design task for creating a worker pool is to allocate the workers. The next step is to schedule the jobs as they come in by distributing them to available workers in the pool. Lastly, we'll need to account for busy states when all the workers are busy. Let's do this.

Allocating pools

Before we think about allocating pools of worker threads, we need to look at the overarching worker pool abstraction. How do we want it to look and behave? Ideally, we want the pool abstraction to look and behave like a plain dedicated worker. We can post a message to the pool and get a promise in response. So while we can't directly...