One of the many reasons given for using microservices rather than a mono repository is that it enforces boundaries between services/modules. However, there are ways to achieve strong boundaries between modules/services in one repository, using tools which are already available: test runners. Given a repository with the following structure: . ├── libraries │ ├── core │ ├── events │ └── ui ├── services │ ├── catalogue │ ├── billing │ └── shipping └── tools └── admin-cli There are a few rules we should enforce:...

Tracking where the time goes in your CI pipeline is an important step towards being able to make it go even faster. Up until somewhat recently, the only way of tracking how long tasks took in CI was either hoping people had wrapped all their commands in time ..., or by reading a timestamped build log and calculating the difference between numbers. Which isn’t great or fun, if we’re being honest....

I haven’t seen Expand-Contract written about in some years, and I think it is a great way of performing database schema migrations without the need for application downtime. I also realised that it also applies to microservices and service-to-service communication in general. The Easy Example One of the two examples given is wanting to change how an address is stored in a database. The schema starts off looking like this:...

Feature flags are a great tool for helping software development; they provide controlled feature rollouts, facilitate A/B testing, and help decouple deployment from release. So when it comes to building our software, why do we treat the CI pipeline without the same level of engineering as the production code? So, why not use feature flags in your CI pipeline? TLDR Reduce the risk of breaking a CI pipeline for all of a project’s developers by using the flagon CLI to query Feature Flags, opting developers into and out of new CI features and processes by targeting groups of developers or branch naming patterns....

Versioning is one of the many hard problems when it comes to writing software. There is no one correct way to do it, and all have various tradeoffs. After reading keep a changelog, I was inspired to implement this into a couple of CLI tools that I am working on at the moment: Flagon (feature flags on the CLI, for CI usage), and Cas (Content Addressable Storage for Make), but I also wanted to solve my versioning and release process....

When migrating to a continuous delivery process, it is often the case that a QA team are worried about what their role is going to be, and how the changes will affect the quality of the software in question. While doing continuous delivery does change the QA process, when done well, it improves everyone’s lives and makes the software better quality. Are silver bullets incoming? Not quite, but we don’t have to make someone’s life worse to improve other people’s lives....

Recently we were having a debate about release processes, and I wrote that deployments are not always equal to releases. also deploy != release —Andy, baiting discussion in Slack This turned out to be somewhat controversial until we discussed what I specifically meant by deploy and release. As with all things, agreeing on definitions or understanding what someone means when they use a specific term is essential, so I thought I would write down a short blog post on it....

On several occasions when building complex projects, I have been tempted to set up Bazel to help speed up the build process; after all, it has a lot to offer: only building what has changed, caching built artifacts, and sharing that cache between machines for even more speed. TLDR We can use Make and a couple of short shell scripts to implement file content-based caching and read/write that cache to remote storage, such as S3....

I write a lot of blog posts which contain code snippets. Like most people, I have done this using a fenced codeblock in markdown which is fine for short blocks of code. The problem occours when I am embedding code from another repository; often there will be tweaks or bug fixes, and keeping the code in the blog post in sync with the code in the other repo is annoying and manual....

This is in response to the recent posts about the death of UML; while I think some parts of UML have fallen ill, the remaining parts are still alive, and useful to this day. TLDR Out of 14 types of diagram there are 3 that I use on a regular basis: Activity Diagram, State Machine Diagram, and Sequence Diagram. I think the Timing Diagram is borderline, but I can only think of a couple of occasions when it has been useful....