Design

A couple incomplete thoughts and questions for those that need to automatically log end users out of web applications. ...

Have you ever considered a service or suite of services and thought, “that looks like a ball of yarn.” There is a tendency amongst those of us who write software for a living to consider systems that are not understood as garbage. Often, this suspicion of poorly understood systems turns out to be unwarranted. What look like obtuse decisions made for no apparent reason turn out to have solid foundation in rationality. Software that looks strange with weird functionality sometimes is that way because strange and weird things were asked of it. ...

We often think about best practices while developing software. Sometimes it is also instructive to contemplate what not to do when writing software. Today’s post covers some logic in AngularJS services which should be avoided save for rare exceptions. ...

It is a good practice to add logging capabilities to applications as they are built. There are a lot of good tutorials on how to setup logging within various applications and software frameworks. It is also instructive to discuss why something is a good practice since understanding why can lead to new insight in how, when, and where to apply said ’thing.’ The point of today’s post is to discuss some scenarios for why application logging is important. This post will be mostly non-technical because the how of logging can be learned with some decent web searches and there is already a wealth of information on logging software on the web. ...

Round robin DNS records are a technique for distributing load across public facing web servers. As an experiment we tried using them in order to distribute load inside of a cluster. We found this approach didn’t work. In this post I’ll discuss round robin load balancing, how it works at a high level, what we did with DNS, why it didn’t work, and what can be done instead. ...

For the love of all that is dear to software development avoid parallel but separate class hierarchies. Today we’re going to talk a little bit about type hierarchy design and why composition is useful to consider in certain scenarios. ...

A 1st generation software product will likely miss the mark. It might have missed being that best that it could be by costing too much, being too complex, or just not targeting the right market. In any case, a 1st product may lead to another, 2nd, product that is cheaper, simpler, or just hits the right notes with the intended customer. Today’s post is about building the wrong product (the 1st one) in the right way so that the 2nd product can be built better, faster. ...

Note I didn’t say always should export objects, but for the sanity of everyone involved, in many cases a required module should return a constructor and not a fully instantiated object. Today’s post is about why your NodeJS modules should look like this: /** * @constructor */ function myConstructor(someDependency) { /* setup my object here */ } module.exports = myConstructor; and not this: var myObj = { myService: new MyService() }; myObj.myFunction = function(foo) { /* do stuff with foo here */ }; module.exports = myObj; ...

Martin Folwer’s blog and website is a common reference for modern design pattern so we will start with his glossary definition for the repository pattern. The linked article contains more detail, but in short a ‘repository’ acts as an data store layer on top of the storage system and provides (more) object oriented methods for accessing said system. Unfortunately, something I have also seen is the over application of this pattern in combination with RDBMS ORMs leading to contorted code with unnecessary interfaces and classes. This post covers what I have seen in some projects in order to provide some of the code smells to avoid. ...

How to represent a blank user input is a reasonably innocent design question. On a couple occasions though I have been bitten by systems that have been designed without considering that question seriously. Maybe it’s a clear choice to some, but today’s post makes an argument that in representing an empty input as a null is better than using a empty or blank string. ...