Interaction with source control is a daily task for most developers, the idea of not managing source code in this way would seem unthinkable. The advantages that effective source control can give have lead many to look to include more of the material and information required to write, deploy and run software to be part of the same standard development practices.
This idea has gone by many names, at WeaveWorks they have coined the term GitOps. Although in their description of the process they assume a container based deployment using Kubernetes, the principles they define for an effective GitOps strategy could be applied too many different deployment scenarios.
The Entire System Described In The Repository
No matter the nature of the software you are writing it will need to be built and deployed. To achieve this most teams will have defined CI/CD pipelines to build and deploy the code to various deployment environments.
A GitOps strategy ensures that these pipelines, and the infrastructure they serve, are declared alongside the source code. By cloning the repo you should have access to all the information required to understand the system.
The Canonical Desired System State Versioned in Git
Once your entire system is under source control then you have a single source of truth for its current state and also for any previous state in the past. Changes to CI\CD and infrastructure are tracked alongside the code of the application allowing you to move back and forth in time and maintain a working system.
The most obvious advantage this gives is in dealing with an unintended breaking change to the application related to CI\CD or infrastructure changes. Without these things being under source control you have to follow a painful process of trying to understand the changes that have been made and defining a plan for undoing these changes or trying to fix forward. A GitOps strategy reduced this task to something as simple as a Git Revert command or redeploying from a previous release branch.
Approved Changes That Can Be Automatically Applied To The System
When applying changes to an applications source code developers are used to going through a review process before changes are applied. This may involve a peer review by another developer and\or by following a shift left strategy it may involve a series of automated tests to ensure correctness.
By following a GitOps strategy these process can be applied to changes to CI\CD and infrastructure as well as code. As with any shift left strategy this reduces the chances of the team being impacted by changes that may inadvertently break pipelines, result in a non-working application after deployment, or unintentionally increase costs due to a misconfigured infrastructure change.
Software Agents to Ensure Correctness and Alert on Divergence
Your ability to follow this principle will vary based in your deployment model, but in essence by having source control be the source of truth for your system it enables software to automatically detect when this doesn't match the reality of your deployment and make the appropriate changes.
Not only do this mean you get to see your changes reflected in your environments at a faster pace it also decreases the time to recover from human error once the bad change set has been reversed.
When looking to apply these principles you will have to analyse how they can best be implemented for your application and the environments you deploy into. As with most philosophies there is no one size fits all approach, the degree to which you are applying these principles maybe an intangible measure rather than an absolute. But as always an appreciation for the benefits is the key, and using this to guide your approach and maximise your effectiveness.
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