Recently, I was asked if I could provide an example of Branch By Abstraction when dealing with feature toggles. As this has come up a few times, I thought a blog post would be a good idea so I can refer others to it later too. The Context As usual, this is some kind of backend (micro)service, and it will send email messages somehow. We will start with two implementations of message sending: the “current” version; which is synchronous, and a “new” version; which is async....

DEPRECATED - This has a race condition! Please see this post for an updated version which works! Following on from the post the other day on setting up DNS forwarding to Consul with SystemD, I wanted also to show how to get Consul up and running under Alpine Linux, as it’s a little more awkward in some respects. To start with, I am going to setup Consul as a service - I didn’t do this in the Ubuntu version, as there are plenty of useful articles about that already, but that is not the case with Alpine....

DEPRECATED - This doesn’t work properly Please see this post for an updated version which works! One of the advantages of using Consul for service discovery is that besides an HTTP API, you can also query it by DNS. The DNS server is listening on port 8600 by default, and you can query both A records or SRV records from it. SRV records are useful as they contain additional properties (priority, weight and port), and you can get multiple records back from a single query, letting you do load balancing client side:...

Last time I wrote about running a RabbitMQ cluster in Nomad, one of the main pieces of feedback I received was about the (lack) of security of the setup, so I decided to revisit this, and write about how to launch as secure RabbitMQ node in Nomad. The things I want to cover are: Username and Password for the management UI Secure value for the Erlang Cookie SSL for Management and AMQP As usual, the demo repository with all the code is available if you’d rather just jump into that....

I had a major problem a few hours before giving my Nomad: Kubernetes Without the Complexity talk this morning: the demo stopped working. Now, the first thing to note is the entire setup of the demo is scripted, and the scripts hadn’t changed. The only thing I had done was restart the machine, and now things were breaking. The Symptoms A docker container started inside the guest VMs with a port mapped to the machine’s public IP wasn’t resolvable outside the host....

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....