Foreword by Ryan Dahl

Ryan Dahl, creator of Node.js

In 2008 I was searching for a new programming platform for making websites. This was more than wanting a new language; indeed, the details of the language mattered very little to me. Rather, I was concerned about the ability to program advanced push features into the website like I had seen in Gmail—the ability for the server to push data to the user instead of having to constantly poll. The existing platforms were tightly coupled to the idea of the server as something that receives a request and issues a response sequentially. To push events to the browser, the platform needed to be able to constantly handle a number of open and mostly idle connections.

I knew how to make this work at the system call layer, in C. If I used only nonblocking sockets, the overhead per connection was very small. In small tests, I could demonstrate a server that could handle thousands of idle connections or pretty massive throughput. I knew that this was the optimal way for a user-space Unix server to be implemented. However, I didn’t want to work in C; I wanted the beautiful fluidness of a dynamic language. Although it was possible to issue the exact system calls I wanted in every programming language, it was very ugly and was always the “alternative” method of socket programming. My theory was that nonblocking sockets were not actually difficult at all, as long as everything was nonblocking.

Google announced Chrome and its new JavaScript engine V8 in late 2008. A faster JavaScript engine made for a faster Web—and V8 made the Web a lot faster. Suddenly there was this idea of a JavaScript arms race between Google, Apple, Mozilla, and Microsoft. This, combined with Doug Crockford’s book JavaScript: The Good Parts (O’Reilly), shifted JavaScript from the language everyone despised to an important language.

I had an idea: nonblocking sockets in JavaScript! Because JavaScript has no existing socket libraries, I could be the first to introduce this new and hopefully better interface. Just take V8 and glue it to my nonblocking C code, and I should be done. I quit my contracting job and began working on this idea full time. Once I made the very first version available, I immediately had users who reported bugs; I started fixing those bugs, and then three years passed.

It turns out that JavaScript jibes extremely well with nonblocking sockets. This was not clear from the start. The closures made everything possible. People were able to build very complex nonblocking servers in just a couple of lines of JavaScript. My initial fear that the system would be unusably niche was quickly alleviated as hackers from all over the world began to build libraries for it. The single event loop and pure nonblocking interface allowed libraries to add more and more complexity without introducing expensive threads.

In Node, users find a system that scales well by default. Because of the choices made in the core system, nothing in the system is allowed to do anything too terrible (such as block the current thread), and thus performance never degrades horribly. It is an order of magnitude better than the traditional blocking approach, where “better” is defined as the amount of traffic it can handle.

These days, Node is being used by a large number of startups and established companies around the world, from Voxer and Uber to Walmart and Microsoft. It’s safe to say that billions of requests are passing through Node every day. As more and more people come to the project, the available third-party modules and extensions grow and increase in quality. Although I was once reserved about recommending it for mission-critical applications, I now heartily recommend Node for even the most demanding server systems.

This book gracefully takes the reader through a discussion of and guided exercises for Node and many third-party modules. By learning the material covered here, you go from basic familiarity with JavaScript to building complex, interactive websites. If you’ve used other server-side web frameworks in the past, you’ll be shocked at how easy it is to build a server in Node.