GitOps with Weaveworks Flux

If you have ever deployed applications to Kubernetes or other platforms, you are probably used to the following approach:

• developers check in code which triggers CI (continuous integration) and eventually results in deployable artifacts
• a release process deploys the artifacts to one or more environments such as a development and a production environment

In the case of Kubernetes, the artifact is usually a combination of a container image and a Helm chart. The release process then authenticates to the Kubernetes cluster and deploys the artifacts. Although this approach works, I have always found this deployment process overly complicated with many release pipelines configured to trigger on specific conditions.

What if you could store your entire cluster configuration in a git repository as the single source of truth and use simple git operations (is there such a thing? 😁) to change your configuration? Obviously, you would need some extra tooling that synchronizes the configuration with the cluster, which is exactly what Weaveworks Flux is designed to do. Also check the Flux git repo.

In this post, we will run through a simple example to illustrate the functionality. We will do the following over two posts:

Post one:

• Create a git repo for our configuration
• Install Flux and use the git repo as our configuration source
• Install an Ingress Controller with a Helm chart

Post two:

• Install an application using standard YAML (including ingress definition)
• Update the application automatically when a new version of the application image is available

Let’s get started!

Create a git repository

To keep things simple, make sure you have an account on GitHub and create a new repository. You can also clone my demo repository. To clone it, use the following command:

Note: if you clone my repo and use it in later steps, the resources I defined will get created automatically; if you want to follow the steps, use your own empty repo

Install Flux

Flux needs to be installed on Kubernetes, so make sure you have a cluster at your disposal. In this post, I use Azure Kubernetes Services (AKS). Make sure kubectl points to that cluster. If you have kubectl installed, obtain the credentials to the cluster with the Azure CLI and then run kubectl get nodes or kubectl cluster-info to make sure you are connected to the right cluster.

It is easy to install Flux with Helm and in this post, I will use Helm v3 which is currently in beta. You will need to install Helm v3 on your system. I installed it in Windows 10’s Ubuntu shell. Use the following command to download and unpack it:

This results in a folder linux-amd64 which contains the helm executable. Make the file executable with chmod +x and copy it to your path as helmv3. Next, run helmv3. You should see the help text:

Now you are ready to install Flux. First, add the FLux Helm repository to allow helmv3 to find the chart:

Create a namespace for Flux:

Install Flux in the namespace with Helm v3:

The above command upgrades Flux but installs it if it is missing (-i). The chart to install is fluxcd/flux. With –wait, we wait until the installation is finished. We will not go into the first two –set options for now. The last option defines the git repository Flux should use to sync the configuration to the cluster. Currently, Flux supports one repository. Because we use a public repository, Flux can easily read its contents. At times, Flux needs to update the git repository. To support that, you can add a deploy key to the repository. First, install the fluxctl tool:

Now run the following commands to obtain the public key to use as deploy key:

The output of the command is something like:

Copy and paste this key as a deploy key for your github repo:

Phew… Flux should now be installed on your cluster. Time to install some applications to the cluster from the git repo.

Note: Flux also supports private repos; it just so happens I used a public one here

Install an Ingress Controller

Let’s try to install Traefik via its Helm chart. Since I am not using traditional CD with pipelines that run helm commands, we will need something else. Luckily, there’s a Flux Helm Operator that allows us to declaratively install Helm charts. The Helm Operator installs a Helm chart when it detects a custom resource definition (CRD) of type helm.fluxcd.io/v1. Let’s first create the CRD for Helm v3:

Next, install the operator:

You didn’t think I found the above myself did you? 😁 It’s from an excellent tutorial here.

When the operator is installed, you should be able to install Traefik with the following YAML:

Just add the above YAML to the GitHub repository. I added it to the ingress folder:

If you wait a while, or run fluxctl sync, the repo gets synced and the resources created. When the helm.fluxcd.io/v1 object is created, the Helm Operator will install the chart in the default namespace. Traefik will be exposed via an Azure Load Balancer. You can check the release with the following command:

Also check that the Traefik pod is created in the default namespace (only 1 replica; the default):

Also check the public IP of Traefik:

We will later use that IP when we define the ingress for our web application.

Conclusion

In this post, you learned a tiny bit about GitOps with WeaveWorks Flux. The concept is simple enough: store your cluster config in a git repo as the single source of truth and use git operations to initiate (or rollback) cluster operations. To start, we simply installed Traefik via the Flux Helm Operator. In a later post, we will add an application and look at image management. There’s much more you can do so stay tuned!