Graphing Node.js Memory Usage with D3.js and Rickshaw

2 min read Michael Carroll on Feb 5, 2015
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How to use Rickshaw, d3.js, and PubNub Pub/Sub Messaging to stream data and publish updates to a real-time chart. In this tutorial, we'll graph Node.js usage.

real-time chart rickshaw d3jsIn our last blog post in our series on using data streaming functionality to create Rickshaw real-time charts, we gave an introduction of Rickshaw, d3.js, and PubNub, and built a basic real-time chart. We strongly recommend checking out that tutorial to learn more about real-time DIY visualizations.

In this blog post (and the video below), we’re going to dig a little deeper and build another real-time chart. We’ll be monitoring Node.js memory usage using Rickshaw, d3.js, and a handy npm module.

The npm module plugs right into our Rickshaw-PubNub library, and contains everything you need to get started right away. It’ll automatically log your memory usage and spawns an express static server.

In the end, you’ll have a real-time chart that looks something like this:

real-time chart rickshaw d3js

How It Works

NodeJS memory usage is exposed through process.memoryUsage().

Every interval_timeout the module publishes the current output of process.memoryUsage() to the suppliedpublish_key and channel on the PubNub network.


There are a lot of moving parts, but a full working chart example is include out of the box.

First, install the module with npm.

Include in your app with {dev: true}. This will spawn an express server on localhost using the supplied port. This is a simple static server that already includes the contents of pubnub-rickshaw.

That’s it! Now when you run your node app, you should see the following:

Visit the url to see a real-time graph of your NodeJS memory profile over time. You can copy this javascript code, modify it, and embed it anywhere. Make sure to set your own channel!

real-time chart rickshaw d3js-1

Read more about pubnub-rickshaw-memory in the full documentation.

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