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

Child Processes

We know that NodeJS uses an evented IO loop as its main concurrency mechanism. This is based on the assumption that our application does a lot of IO and very little CPU-intensive work. This is probably true for the majority of handlers in our code. However, there's always a particular edge case that requires more CPU time than usual.

In this section, we'll discuss how handlers can block the IO loop, and why all it takes is one bad handler to ruin the experience for everyone else. Then, we'll look at ways to get around this limitation by forking new Node child processes. We'll also look at how to spawn other non-Node processes in order to get the data that we need.

Blocking the event loop

In Chapter 8, Evented IO with NodeJS, we saw an example that demonstrated how one handler can block the entire IO event loop while performing expensive CPU operations. We're going to reiterate this point here to highlight the full scope of the problem. It's not just one handler that we're blocking...