In the previous post, I deployed AKS, Nginx, External DNS, Helm Operator and Flux with a YAML pipeline in Azure DevOps. Flux got linked to a git repo that contains a bunch of yaml files that deploy applications to the cluster but also configures Azure Monitor. Flux essentially synchronizes your cluster with the configuration in the git repository.
In production, it is not a good idea to simply drop in some yaml and let Flux do its job. Similar to traditional software development, you want to run some tests before you deploy. For Kubernetes yaml files, kubeval is a tool that can run those tests.
I refactored the git repository to have all yaml files in a config folder. To check all yaml files in that folder, the following command can be used:
With -d you specify the folder (and all its subfolders) where kubeval should look for yaml files. The –strict option checks for properties in your yaml file that are not part of the official schema. If you know you need those, you can leave out –strict. With –ignore-missing-schemas, kubeval will ignore yaml files that use custom schemas not in the Kubernetes OpenAPI spec. In my case for instance, the yaml file that deploys a Helm chart (of kind HelmRelease) is such a file. You can also instruct kubeval to ignore specific “kinds” with –skip-kinds. Here’s the result of running the command:
Using a GitHub action
To automate the testing of your files, you can use any CI system like Azure DevOps, CircleCI, etc… In my case, I decided to use a GitHub action. See the getting started for more information about the basics of GitHub Actions. The action I created is easy (hey, it’s my first time using Actions 😊):
An action is defined in yaml 😉 and consists of jobs and steps, similarly to Azure DevOps and the likes. The action is run on Ubuntu (hosted by GitHub) and uses an action from the marketplace called Kubernetes toolset. You can easily search for actions in the editor:
The first step uses an action to checkout your code. Indeed, you need to do that explicitly. Then we use the Kubernetes Toolset to give us access to all kinds of Kubernetes related tools such as kubectl and kubeval. The toolset is just a container which you’ll see getting pulled at runtime. After that, we simple run kubeval in the container which will have mounted the working directory which also contains your checked out code.
In the repository settings, I added a branch protection rule that requires a pull request review before merging plus a status check that must pass (the action):
The pull request below shows a check that did not pass, a violation of the –strict setting in error.yaml:
There are many other tools and techniques that can be used to validate your configuration but this should get you started with some simple checks on yaml files.
As a last note, know that kubeval generates schemas from the Kubernetes OpenAPI specs. You can set the version of Kubernetes with the -v option.
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:
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
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
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.
az aks get-credentials -n CLUSTER_NAME -g RESOURCE_GROUP
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:
curl -sSL "https://get.helm.sh/helm-v3.0.0-beta.3-linux-amd64.tar.gz" | tar xvz
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:
The Kubernetes package manager
Common actions for Helm:
- helm search: search for charts
- helm fetch: download a chart to your local directory to view
- helm install: upload the chart to Kubernetes
- helm list: list releases of charts
Now you are ready to install Flux. First, add the FLux Helm repository to allow helmv3 to find the chart:
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:
curl -sL https://fluxcd.io/install | sh
Now run the following commands to obtain the public key to use as deploy key:
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:
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:
kubectl get helmreleases.helm.fluxcd.io
NAME RELEASE STATUS MESSAGE AGE
traefik traefik deployed helm install succeeded 15m
Also check that the Traefik pod is created in the default namespace (only 1 replica; the default):
kubectl get po
NAME READY STATUS RESTARTS AGE
traefik-86f4c5f9c9-gcxdb 1/1 Running 0 21m
Also check the public IP of Traefik:
kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP
traefik LoadBalancer 10.0.8.59 126.96.36.199
We will later use that IP when we define the ingress for our web application.
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!