Update If you want a secure version of this cluster, see Running a Secure RabbitMQ Cluster in Nomad. RabbitMQ is the centre of a lot of micros service architectures, and while you can cluster it manually, it is a lot easier to use some of the auto clustering plugins, such as AWS (EC2), Consul, Etcd, or Kubernetes. As I like to use Nomad for container orchestration, I thought it would be a good idea to show how to cluster RabbitMQ when it is running in a Docker container, on an unknown host (i....

In my previous post, I glossed over one of the most important and useful parts of Immutable Infrastructure: Testability. There are many kinds of tests we can write for our infrastructure, but they should all be focused on the machine/service and maybe it’s nearest dependencies, not the entire system. While this post focuses on testing a full machine (both locally in a VM, and remotely as an Amazon EC2 instance), it is also possible to do most of the same kind of tests against a Docker container....

I wanted to show request charts (similar to the network tab in firefox) for requests across our microservices but wanted to do so in the least invasive way possible. We already use LogStash to collect logs from multiple hosts (via FileBeat) and forward them on to ElasticSearch, so perhaps I can do something to also output from LogStash to a tracing service. There are a number of tracing services available (AppDash, Jaeger, Zipkin), but unfortunately LogStash doesn’t have plugins for any of them or for OpenTracing....

Well, for Applications & Services at least. For libraries, SemVer is the way to go, assuming you can agree on what a breaking change is defined as. But when it comes to Applications (or SaaS products, websites, etc.) SemVer starts to break down. The problem starts with the most obvious: What is a breaking change? How about a minor change? What’s in a change? For example, if we were to change the UI of a web application, which caused no backend changes, from the user perspective it is probably a breaking change, but not from the developers perspective....

…about GitHub open source commit streak. This is, I think, partially triggered by Marc Gravell’s post. I currently have had a GitHub commit streak going on 1878 days. The other night I realised, that I don’t care about it any more, and more so, I’m not sure why I did to start with. I didn’t even mean to start doing it. I just noticed one day that I had done something every day for a couple of weeks, and vaguely wondered how long I could keep that up for....

One of the reasons people list for using MicroServices is that it helps enforce separation of concerns. This is usually achieved by adding a network boundary between the services. While this is useful, it’s not without costs; namely that you’ve added a set of new failure modes: the network. We can achieve the same separation of concerns within the same codebase if we put our minds to it. In fact, this is what Simon Brown calls a Modular Monolith, and DHH calls the Majestic Monolith....

At NDC Oslo this year, I attended Adam Ralph’s talk on Finding Your Service Boundaries. I enjoyed it a lot, and once the video came out, I rewatched it, and decided to have a go at doing a “sketchnotes”, which I shared on Twitter, which people liked! I’ve never done one before, but it was pretty fun. I made it in OneNote, zoomed out a lot, and took a screenshot....

After my previous post on Validating Your Configuration, one of my colleagues made an interesting point, paraphrasing: I want to know if the configuration is valid earlier than that. At build time preferably. I don’t want my service to not start if part of it is invalid. There are two points here, namely when to validate, and what to do with the results of validation. Handling Validation Results If your configuration is invalid, you’d think the service should fail to start, as it might be configured in a dangerous manner....

Feature Toggles are a great way of helping to deliver working software, although there are a few things which could go wrong. See my talk Feature Toggles: The Good, The Bad and The Ugly for some interesting stories and insights on it! I was talking with a colleague the other day about how you could go about implementing Feature Toggles in a centralised manner into an existing system, preferably with a little overhead as possible....

As I have written many times before, your application’s configuration should be strongly typed and validated that it loads correctly at startup. This means not only that the source values (typically all represented as strings) can be converted to the target types (int, Uri, TimeSpan etc) but that the values are semantically valid too. For example, if you have a web.config file with the following AppSetting, and a configuration class to go with it:...