Sharing Docker Layers Between Build Agents

Recently, I noticed that when we pull a new version of our application’s docker container, it fetches all layers, not just the ones that change. The problem is that we use ephemeral build agents, which means that each version of the application is built using a different agent, so Docker doesn’t know how to share the layers used. While we can pull the published container before we run the build, this only helps with the final stage of the build....

May 14, 2020 · 4 min

Service Mesh with Consul Connect (and Nomad)

When it comes to implementing a new feature in an application’s ecosystem, I don’t like spending my innovation tokens unless I have to, so I try not to add new tools to my infrastructure unless I really need them. This same approach comes when I either want, need, or have been told, to implement a Service Mesh. This means I don’t instantly setup Istio. Not because it’s bad - far from it - but because it’s extra complexity I would rather avoid, unless I need it....

May 4, 2020 · 6 min

Observability Without Honeycomb

Before I start on this, I want to make it clear that if you can buy Honeycomb, you should. Outlined below is how I started to add observability to an existing codebase which already had the ELK stack available, and was unable to use Honeycomb. My hope, in this case, is that I can demonstrate how much value observability gives, and also show how much more value you would get with an excellent tool, such as Honeycomb....

March 15, 2020 · 7 min

Nomad Isolated Exec

One of the many features of Nomad that I like is the ability to run things other than Docker containers. It has built-in support for Java, QEMU, and Rkt, although the latter is deprecated. Besides these inbuilt “Task Drivers” there are community maintained ones too, covering Podman, LXC, Firecraker and BSD Jails, amongst others. The one I want to talk about today, however, is called exec. This Task Driver runs any given executable, so if you have an application which you don’t want (or can’t) put into a container, you can still schedule it with Nomad....

February 29, 2020 · 4 min

Consul DNS Fowarding in Alpine, revisited

I noticed when running an Alpine based virtual machine with Consul DNS forwarding set up, that sometimes the machine couldn’t resolve *.consul domains, but not in a consistent manner. Inspecting the logs looked like the request was being made and responded to successfully, but the result was being ignored. After a lot of googling and frustration, I was able to track down that it’s down to a difference (or optimisation) in musl libc, which glibc doesn’t do....

December 30, 2019 · 4 min

Libvirt Hostname Resolution

I use Vagrant when testing new machines and experimenting locally with clusters, and since moving (mostly) to Linux, I have been using the LibVirt Plugin to create the virtual machines. Not only is it significantly faster than Hyper-V was on windows, but it also means I don’t need to use Oracle products, so it’s win-win really. The only configuration challenge I have had with it is setting up VM hostname resolution, and as I forget how to do it each time, I figured I should write about it....

December 22, 2019 · 3 min

Nomad Good, Kubernetes Bad

I will update this post as I learn more (both positive and negative), and is here to be linked to when people ask me why I don’t like Kubernetes, and why I would pick Nomad in most situations if I chose to use an orchestrator at all. TLDR: I don’t like complexity, and Kubernetes has more complexity than benefits. Operational Complexity Operating Nomad is very straight forward. There are very few moving parts, so the number of things which can go wrong is significantly reduced....

November 21, 2019 · 6 min

Creating a Vault instance with a TLS Consul Cluster

So we want to set up a Vault instance, and have it’s storage be a TLS based Consul cluster. The problem is that the Consul cluster needs Vault to create the certificates for TLS, which is quite the catch-22. Luckily for us, quite easy to solve: Start a temporary Vault instance as an intermediate ca Launch Consul cluster, using Vault to generate certificates Destroy temporary Vault instance Start a permanent Vault instance, with Consul as the store Reprovision the Consul cluster with certificates from the new Vault instance There is a repository on Github with all the scripts used, and a few more details on some options....

October 6, 2019 · 3 min

Consul DNS Fowarding in Ubuntu, revisited

I was recently using my Hashibox for a test, and I noticed the DNS resolution didn’t seem to work. This was a bit worrying, as I have written about how to do DNS resolution with Consul forwarding in Ubuntu, and apparently something is wrong with how I do it. Interestingly, the Alpine version works fine, so it appears there is something not quite working with how I am configuring Systemd-resolved....

September 24, 2019 · 7 min

Creating a TLS enabled Consul cluster

This post is going to go through how to set up a Consul cluster to communicate over TLS. I will be using Vagrant to create three machines locally, which will form my cluster, and in the provisioning step will use Vault to generate the certificates needed. How to securely communicate with Vault to get the TLS certificates is out of scope for this post. Host Configuration Unless you already have Vault running somewhere on your network, or have another mechanism to generate TLS certificates for each machine, you’ll need to start and configure Vault on the Host machine....

September 14, 2019 · 6 min