Node.js and its Single-Threaded World

If you are a web developer or a Computer Science student you must have heard of Node.js. Today I shall discuss with you the factors that make Node.js impressively faster than its counterparts.

Just a brief introduction for the first-time listeners before we come to the point.

Node.js is an open-source, cross-platform JavaScript run-time environment that executes JavaScript code out of a web-browser. With Node.js developers can use JavaScript to write command-line tools and for server-side scripting to produce dynamic web content even before the webpage is forwarded to the user's browser.

Node.js has given JavaScript the power to do things that languages like Java and Python can do, and in an even efficient and faster way. The original documentation defines Node.js as a platform built on Google's V8 engine, which is Chrome’s JavaScript runtime.

Since its initial release in 2010, Node.js has become the go-to option for various organizations. Companies such as IBM, LinkedIn, Microsoft, Netflix, PayPal, Walmart, Yahoo! among others have switched (partially if not wholly) to Node.js.   

Before we proceed further, we must know what an asynchronous pattern is.

Asynchronous method invocation is a model in which the program is not blocked while waiting for a called piece of code to terminate. Instead, the calling part of the code is informed when the response comes. Until then, the subsequent part of the code is run.

Now, let’s come to the point.

Node.js teams up the Google V8, a message dispatcher (also known as event loop), and an input/output (I/O) application programming interface (API) which handles hardware events by making a request, to a central event provider.

Generally, the I/O takes time and blocks other functions. But Node.js takes care that such blockages don’t happen. Node.js’ message dispatcher functions asynchronously with the message creator (also termed as thread pool) which has a queue of events and sends the message (event call) for a specific event when its request is granted. This ensures that the server does not wait for an API to send back any data and moves on to the next API. The message dispatcher’s event handling mechanism assists the server to obtain a reply from the preceding API call later on. This imparts Node.js a non-blocking nature which increases the server’s request handling efficiency.

Unlike other server-side technologies like ASP.NET, Java Servers, PHP, and Ruby, Node.js is single-threaded which gives it first-rate speed. Traditionally, multi-threading is considered superior to single-threading and has been employed to enhance the utilization of the CPU by allowing parallel execution of two or more requests. In multithreading servers, instead of processing the inward requests in the same thread that receives the client connection, the connection is dispensed off to another thread.

In Node.js, all the requests with a set of shared resources are run by the main event loop, which is single-threaded which makes Node.js a single-threaded language. All the requests are handled by this one thread only.

But, as the kernel doesn’t provide for performing everything asynchronously, most of the I/O works are run on separate threads. Node.js has a collection of threads. It locks a thread for the period of a process so it may carry on implementing the event loop without blocking. This helps in providing services to a greater number of requests than other servers, like Apache.

Node.js’ single-threaded architecture along with its event-driven design supports concurrency via the concept of events and callbacks. Callbacks are functions that support asynchronous method calls. An asynchronous function accepts a callback as its last parameter and the callback method accepts an error as its first parameter. A callback function is basically the event handler. This lack of need for multiple threads saves a lot of resources and memory and makes Node.js fast.

The above features make Node.js efficient, effective, lightweight, and extremely fast which qualifies it as the best option for data-intensive real-time applications that run across distributed devices and require to handle a large number of requests at a time. It should be noted that Node.js is itself not a server but a platform over which a server is built.