Having recently finished reading the Building Evolutionary Architectures: Support Constant Change book, I got to thinking about a system which was fairly representative of an architecture which was fine for it’s initial version, but it’s usage had outgrown the architecture. Example System: Document Storage The system in question was a file store for a multi user, internal, desktop based CRM system. The number of users was very small, and the first implementation was just a network file share....

It’s no secret I am a fan of strong typing - not only do I talk and blog about it a lot, but I also have a library called Stronk which provides strong typed configuration for non dotnet core projects. The problem I come across often is large configurations. For example, given the following project structure (3 applications, all reference the Domain project): DemoService `-- src |-- Domain | |-- Domain....

I’ve been on-call for work over the last week for the first time, and while it wasn’t as alarming (heh) as I thought it might be, I have had a few thoughts on it. Non-action Alarms We have an alarm periodically about an MVC View not getting passed the right kind of model. The resolution is to mark the bug as completed/ignored in YouTrack. Reading the stack trace, I can see that the page is expecting a particular model, but is being given a HandleErrorInfo model, which is an in built type....

I gave a little talk at work recently on my use of Vagrant, what it is, and why it is still useful in a world full of Docker containers. So, What is Vagrant? Vagrant is a product by Hashicorp, and is for scripting the creation of (temporary) virtual machines. It’s pretty fast to create a virtual machine with too, as it creates them from a base image (known as a “box”....

We have a service which consumes messages from a RabbitMQ queue - for each message, it makes a few http calls, collates the results, does a little processing, and then pushes the results to a 3rd party api. One of the main benefits to having this behind a queue is our usage pattern - the queue usually only has a few messages in it per second, but periodically it will get a million or so messages within 30 minutes (so from ~5 messages/second to ~560 messages/second....

While I was developing my Crispin project, I ended up needing to create a bunch of implementations of a single interface, and then use all those implementations at once (for metrics logging). The interface looks like so: public interface IStatisticsWriter { Task WriteCount(string format, params object[] parameters); } And we have a few implementations already: LoggingStatisticsWriter - writes to an ILogger instance StatsdStatisticsWriter - pushes metrics to StatsD InternalStatisticsWriter - aggregates metrics for exposing via Crispin’s api To make all of these be used together, I created a fourth implementation, called CompositeStatisticsWriter (a name I made up, but apparently matches the Gang of Four definition of a composite!...

When building libraries, not only is it a good idea to have a large suite of Unit Tests, but also a suite of Integration Tests. For one of my libraries (RabbitHarness) I have a set of tests which check it behaves as expected against a real instance of RabbitMQ. Ideally these tests will always be run, but sometimes RabbitMQ just isn’t available such as when running on AppVeyor builds, or if I haven’t started my local RabbitMQ Docker container....

This post is a summary of a stream I did last night where I implemented all of this. If you want to watch me grumble my way through it, it’s available on YouTube here. In my Crispin project, I wanted the ability to support loading Toggles by both name and ID, for all operations. As I use mediator to send messages from my controllers to the handlers in the domain, this means that I had to either:...

The trouble with testing containers is that usually the test ends up very tightly coupled to the implementation. Let’s see an example. If we start off with an interface and implementation of a “cache”, which in this case is just going to store a single string value. public interface ICache { string Value { get; set; } } public class Cache { public string Value { get; set; } } We then setup our container (StructureMap in this case) to return the same instance of the cache whenever an ICache is requested:...

TLDR: I still don’t like Repositories! Recently I had a discussion with a commenter on my The problems with, and solutions to Repositories post, and felt it was worth expanding on how I don’t use repositories. My applications tend to use the mediator pattern to keep things decoupled (using the Mediatr library), and this means that I end up with “handler” classes which process messages; they load something from storage, call domain methods, and then write it back to storage, possibly returning some or all the data....