node.js Archives - Dots and Brackets: Code Blog

Creating collectd data source in JavaScript

Builds graph with data collected by JavaScript app

Exec Plugin

In the variety of collectd plugins there’s one ‘to rule them all’. If due to some course of events all collectd plugins except for Exec would be taken from you, you’d still be able to restore all its functionality with Exec.

As the name suggests, Exec starts external program or script and interprets its output as source of data. To be specific, it looks for lines that follow this scheme:

PUTVAL hostname/source-instance/datatype-instance [Interval=seconds] timestamp:value[:value..]

1	PUTVAL hostname/source-instance/datatype-instance [Interval=seconds] timestamp:value[:value..]

To be even more specific, these lines would work:

PUTVAL myhost/cpu-0/cpu-system interval=10 N:51
PUTVAL hostname/vm_count/gauge 1484012951:U

1 2	PUTVAL myhost/cpu-0/cpu-system interval=10 N:51 PUTVAL hostname/vm_count/gauge 1484012951:U

What’s interesting, Exec doesn’t specify in what language script should be written, so anything, including JavaScript, might work. In fact, using JavaScript would be beneficial in some scenarios, e.g. when dealing with RESTful services returning JSON.

Before we try JavaScript app as data source for collectd, let’s talk about PUTVAL lines a little bit more. Continue reading “Creating collectd data source in JavaScript”

Using ZeroMQ with Docker

ZeroMQ, Node.js and Docker

Last time we built three client-server Node.js apps that were talking to each other using ZeroMQ. However, running both client and server on localhost is a little bit lame. Let’s put them into containers! They’ll still be lame, but now with Docker around.

So, here’s the plan: let’s see what we need to do to last week’s fire-and-forget ZeroMQ app, so its client and server can work and communicate from within Docker containers. Continue reading “Using ZeroMQ with Docker”

Inter-service messaging with ZeroMQ and Node.js

ZeroMQ is small, fast and very easy to use messaging library, which works equally well both within the same process and over the network. Despite being written in C++, it has bindings for most of the languages you can come up with. And it’s free. Hurrah!

Working with ZeroMQ resembles working with TCP/UDP sockets. In fact, ZeroMQ endpoints are called sockets. You create one, bind it or connect to certain address, and then magic begins… But let’s see some code first and dive into the details as we go. Continue reading “Inter-service messaging with ZeroMQ and Node.js”

3 ways to dockerize existing Node.js app

Dockerize all the things Imagine you have Node.js app you would like to run from within Docker container. Maybe you want to check if it still works on ‘another’ machine, or it’s a test run before adopting containers as the way of software delivery. Reasons may vary.

In order to have something tangible, let’s pick hello.js app which prints out ubiquitous ‘Hello World’:

var http = require('http');
	
http.createServer(function (_, response) {
		response.writeHead(200, {"Content-Type": "text/plain"});
		response.end("Hello World\n");
	})
	.listen(8080);

var http = require('http');

http.createServer(function (_, response) {

response.writeHead(200, {"Content-Type": "text/plain"});

response.end("Hello World\n");

})

.listen(8080);

localhost-hello
How do we put it into container? Continue reading “3 ways to dockerize existing Node.js app”

Playing with microservices

Recently I was asked to build a small internal app: dynamic dashboard for one of our projectors, which are hanging all over the office and display some company info onto the walls: customer statistics, server-to-server latency, what tasks are in development, etc. My particular goal was to add release and builds statistics: build duration, failed/unreliable tests and anything else that could motivate us to produce more stable builds.

We store all relevant data in Google BigQuery and the whole task is basically to extract build results from the storage and present it in clear and simple way. Quite trivial. Continue reading “Playing with microservices”