Getting started with Node.js
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Taking a hot shower after a tiring day is very relaxing. So I turn on the water heater and stand there waiting for water to be warm enough. Wait, ridiculous. Why am I waiting there. Can’t I do other things while heater does it’s job? If this is how I live my life then it’s pretty inefficient. I need to start living asynchronously. What do I mean? Lets say I’m chatting with my busy friend who replies really slow. If I sit idly doing nothing while waiting for his messages you would think I’m dumb and waste a lot of time doing absolutely nothing. A better thing to do is keep doing you job and every time you receive a message reply back quickly. This is of living asynchronously. Keeping this in mind lets talk about node.
Node.js is a JavaScript run-time built on chrome’s V8 JavaScript engine. Node.js uses a event-driven non-blocking IO model that makes it lightweight and efficient.
When I first heard about Node.js buzz I was curious why people say its fast and scale-able? I decided to play with node’s API but I had no idea what non-blocking IO meant and how does that make node lightweight and efficient. So I started with their ‘hello world’ server example and ended up loving Node.js and JavaScript.
What is Node.js?
Generally, web browser is where most programmers learn basic JavaScript. We never actually give a thought to JavaScript engine, the part of the browser that makes JavaScript tick. Google chrome’s JavaScript engine named V8 is really fast and it’s open source. V8 is responsible for turning your code into machine instructions. Ryan Dahl, the creator of Node.js, took this engine, added features around it and gave JavaScript all kinds of superpowers. We can write JavaScript code that can do all sort stuff from networking to concatenating bunch of CSS files and node will run it for us. What makes Node fast and efficient is its event driven non-blocking input output way of doing things and single threaded approach makes it lightweight. Let’s elaborate on it.
Take example of a typical website. Generally there are three pillars to it.You application code that manipulates the data, database of the application and the environment in which your code resides. When a request for content hits your application, your code will fire a query on database. Now if your database if slow for some reason,your code waits there wasting CPU cycles. Why should your app wait for database to finish its operations instead of serving other requests. When database is ready to provide data it should notify your code, hey I’m ready with the data. Node does this.
Following code is example of blocking code
result = query(‘select * from mytable’);
console.log(result);And this is the asynchronous form.
query_finished=function(result){
console.log(result);
}
query('select * from mytable',query_finished);//next line of code runs
In send example we are telling JavaScript to call the database and proceed to next line of code. We are also telling it tot call query finished function once the database is ready. This is possible because of event driven nature of JavaScript. That means every time database is finished with the query, an event is fired. The query_finished function is listening for that event and logging result.
Multi-threaded Vs Single-threaded
If you wanna serve a lot of requests at a time then why not do multi-threading? Servers like Apache use multi-threading. That means it spawns a new thread for every new client. Each thread requires certain amount of RAM. Lets do some Math. Suppose your server machine has 2GB RAM and this RAM is shared between your database server,your code and other processes running on your server machine. Now consider high traffic situation. A lot of threads are created.They eat up considerable part of RAM and after a limit your whole machine just slows down because it runs out of memory. Now imagine your application is data-intensive like an ecommerce store, there will be lot of database input-output or file input-output or both. That means a lot waiting. It can not handle a lot of requests if your machine has less resources. Hence not scalable. Node.js uses single threaded event-driven approach which makes it light weight on resources and efficient. I’ll elaborate on that when we discuss event loop.
I’m super excited to share these little adventures with you. We will begin with ‘Hello World’ program and then move towards building a fully functional web server. Hence we will need to pay attention to details like building a form parser, templating engine, HTTP headers.
Wait a minute. Why do we need to build a web server ourselves? Node has one of the best community and the largest eco-system of ‘ready-to-go’ libraries. I agree but building stuff from scratch gives you a robust understanding of concepts like network protocols,object oriented design, character encoding and lots of other stuff that makes programming super cool. Besides you get better at debugging code and hey, who knows you might need to build your own library. One of the reason to approach Node from scratch is to learn JavaScript. Yes I said that. Don’t worry if you are not a JavaScript Pro. I’m assuming only three things.
- You know basic JavaScript.
- You have Node.js installed
- You won’t copy paste code snippets.
Happy coding.
