What is GitOps?
GitOps is a way to do Continuous Delivery, it works by using Git as a source of truth for declarative infrastructure and workloads. For Kubernetes this means using
git push instead of
kubectl create/apply or
In a traditional CICD pipeline, CD is an implementation extension powered by the continuous integration tooling to promote build artifacts to production. In the GitOps pipeline model, any change to production must be committed in source control (preferable via a pull request) prior to being applied on the cluster. This way rollback and audit logs are provided by Git. If the entire production state is under version control and described in a single Git repository, when disaster strikes, the whole infrastructure can be quickly restored from that repository.
To better understand the benefits of this approach to CD and what the differences between GitOps and Infrastructure-as-Code tools are, head to the Weaveworks website and read GitOps - What you need to know article.
In order to apply the GitOps pipeline model to Kubernetes you need three things:
- a Git repository with your workloads definitions in YAML format, Helm charts and any other Kubernetes custom resource that defines your cluster desired state (I will refer to this as the config repository)
- a container registry where your CI system pushes immutable images (no latest tags, use semantic versioning or git commit sha)
- an operator that runs in your cluster and does a two-way synchronization:
- watches the registry for new image releases and based on deployment policies updates the workload definitions with the new image tag and commits the changes to the config repository
- watches for changes in the config repository and applies them to your cluster
I will be using GitHub to host the config repo, Docker Hub as the container registry and Weave Flux OSS as the GitOps Kubernetes Operator.
Install Helm and Tiller
If you don't have Helm CLI installed, on macOS you can use
brew install kubernetes-helm.
Create a service account and a cluster role binding for Tiller:
kubectl -n kube-system create sa tiller kubectl create clusterrolebinding tiller-cluster-rule \ --clusterrole=cluster-admin \ --serviceaccount=kube-system:tiller
Note that on GKE you need to create an admin cluster user for yourself:
kubectl create clusterrolebinding "cluster-admin-$(whoami)" \ --clusterrole=cluster-admin \ --user="$(gcloud config get-value core/account)"
Deploy Tiller in kube-system namespace:
helm init --skip-refresh --upgrade --service-account tiller
Install Weave Flux
The first step in automating Helm releases with Weave Flux is to create a Git repository with your charts source code. You can fork the gitops-helm project and use it as a template for your cluster config.
If you fork, update the release definitions with your Docker Hub repository and GitHub username located in
\releases(dev/stg/prod)\podinfo.yaml in your master branch before proceeding.
Add the Weave Flux chart repo:
helm repo add weaveworks https://weaveworks.github.io/flux
Install Weave Flux and its Helm Operator by specifying your fork URL (replace
stefanprodan with your GitHub username):
helm install --name flux \ --set rbac.create=true \ --set helmOperator.create=true \ --set firstname.lastname@example.org:stefanprodan/gitops-helm \ --namespace flux \ weaveworks/flux
The Flux Helm operator provides an extension to Weave Flux that automates Helm Chart releases for it. A Chart release is described through a Kubernetes custom resource named HelmRelease. The Flux daemon synchronizes these resources from git to the cluster, and the Flux Helm operator makes sure Helm charts are released as specified in the resources.
Note that Flux Helm Operator works with Kubernetes 1.9 or newer.
At startup Flux generates a SSH key and logs the public key. Find the SSH public key with:
kubectl -n flux logs deployment/flux | grep identity.pub | cut -d '"' -f2
In order to sync your cluster state with Git you need to copy the public key and create a deploy key with write access on your GitHub repository.
Open GitHub, navigate to your fork, go to Setting > Deploy keys click on Add deploy key, check Allow write access, paste the Flux public key and click Add key.
GitOps pipeline example
The config repo has the following structure:
├── charts │ └── podinfo │ ├── Chart.yaml │ ├── README.md │ ├── templates │ └── values.yaml ├── hack │ ├── Dockerfile.ci │ └── ci-mock.sh ├── namespaces │ ├── dev.yaml │ └── stg.yaml └── releases ├── dev │ └── podinfo.yaml └── stg └── podinfo.yaml
I will be using podinfo to demonstrate a full CI/CD pipeline including promoting releases between environments.
I'm assuming the following Git branching model:
- dev branch (feature-ready state)
- stg branch (release-candidate state)
- master branch (production-ready state)
When a PR is merged in the dev or stg branch will produce a immutable container image as in
hack dir you can find a script that simulates the CI process for dev and stg. The
ci-mock.sh script does the following:
- pulls the podinfo source code from GitHub
- generates a random string and modifies the code
- generates a random Git commit short SHA
- builds a Docker image with the format:
- pushes the image to Docker Hub
Let's create an image corresponding to the
dev branch (replace
stefanprodan with your Docker Hub username):
$ cd hack && ./ci-mock.sh -r stefanprodan/podinfo -b dev Sending build context to Docker daemon 4.096kB Step 1/15 : FROM golang:1.10 as builder .... Step 9/15 : FROM alpine:3.7 .... Step 12/15 : COPY --from=builder /go/src/github.com/stefanprodan/k8s-podinfo/podinfo . .... Step 15/15 : CMD ["./podinfo"] .... Successfully built 71bee4549fb2 Successfully tagged stefanprodan/podinfo:dev-kb9lm91e The push refers to repository [docker.io/stefanprodan/podinfo] 36ced78d2ca2: Pushed
Inside the charts directory there is a podinfo Helm chart. Using this chart I want to create a release in the
dev namespace with the image I've just published to Docker Hub. Instead of editing the
values.yaml from the chart source I will create a
apiVersion: flux.weave.works/v1beta1 kind: HelmRelease metadata: name: podinfo-dev namespace: dev labels: chart: podinfo annotations: flux.weave.works/automated: "true" flux.weave.works/tag.chart-image: glob:dev-* spec: releaseName: podinfo-dev chart: git: email@example.com:stefanprodan/gitops-helm path: charts/podinfo ref: master values: image: stefanprodan/podinfo:dev-kb9lm91e replicaCount: 1
Flux Helm release fields:
metadata.nameis mandatory and needs to follow Kubernetes naming conventions
metadata.namespaceis optional and determines where the release is created
metadata.labels.chartis mandatory and should match the directory containing the chart
spec.releaseNameis optional and if not provided the release name will be $namespace-$name
spec.chart.pathis the directory containing the chart, given relative to the repository root
spec.valuesare user customizations of default parameter values from the chart itself
The options specified in the HelmRelease
spec.values will override the ones in
values.yaml from the chart source.
flux.weave.works annotations I instruct Flux to automate this release. When a new tag with the prefix
dev is pushed to Docker Hub, Flux will update the image field in the yaml file, will commit and push the change to Git and finally will apply the change on the cluster.
podinfo-dev HelmRelease object changes inside the cluster, Kubernetes API will notify the Flux Helm Operator and the operator will perform a Helm release upgrade.
$ helm history podinfo-dev REVISION UPDATED STATUS CHART DESCRIPTION 1 Fri Jul 20 16:51:52 2018 SUPERSEDED podinfo-0.2.0 Install complete 2 Fri Jul 20 22:18:46 2018 DEPLOYED podinfo-0.2.0 Upgrade complete
The Flux Helm Operator reacts to changes in the HelmResources collection but will also detect changes in the charts source files. If I make a change to the podinfo chart, the operator will pick that up and run an upgrade.
$ helm history podinfo-dev REVISION UPDATED STATUS CHART DESCRIPTION 1 Fri Jul 20 16:51:52 2018 SUPERSEDED podinfo-0.2.0 Install complete 2 Fri Jul 20 22:18:46 2018 SUPERSEDED podinfo-0.2.0 Upgrade complete 3 Fri Jul 20 22:39:39 2018 DEPLOYED podinfo-0.2.1 Upgrade complete
Now let's assume that I want to promote the code from the
dev branch into a more stable environment for others to test it. I would create a release candidate by merging the podinfo code from
dev into the
stg branch. The CI would kick in and publish a new image:
$ cd hack && ./ci-mock.sh -r stefanprodan/podinfo -b stg Successfully tagged stefanprodan/podinfo:stg-9ij63o4c The push refers to repository [docker.io/stefanprodan/podinfo] 8f21c3669055: Pushed
Assuming the staging environment has some sort of automated load testing in place, I want to have a different configuration than dev:
apiVersion: flux.weave.works/v1beta1 kind: HelmRelease metadata: name: podinfo-rc namespace: stg labels: chart: podinfo annotations: flux.weave.works/automated: "true" flux.weave.works/tag.chart-image: glob:stg-* spec: releaseName: podinfo-rc chart: git: firstname.lastname@example.org:stefanprodan/gitops-helm path: charts/podinfo ref: master values: image: stefanprodan/podinfo:stg-9ij63o4c replicaCount: 2 hpa: enabled: true maxReplicas: 10 cpu: 50 memory: 128Mi
With Flux Helm releases it's easy to manage different configurations per environment. When adding a new option in the chart source make sure it's turned off by default so it will not affect all environments.
If I want to create a new environment, let's say for hotfixes testing, I would do the following:
- create a new namespace definition in
- create a dir
- create a HelmRelease named
- set the automation filter to
- make the CI tooling publish images from my hotfix branch to
Production promotions with sem ver
For production, instead of tagging the images with the Git commit, I will use Semantic Versioning.
Let's assume that I want to promote the code from the
stg branch into
master and do a production release. After merging
master via a pull request, I would cut a release by tagging
master with version
When I push the git tag, the CI will publish a new image in the
$ cd hack && ./ci-mock.sh -r stefanprodan/podinfo -v 0.4.10 Successfully built f176482168f8 Successfully tagged stefanprodan/podinfo:0.4.10
If I want to automate the production deployment based on version tags, I would use
semver filters instead of
apiVersion: flux.weave.works/v1beta1 kind: HelmRelease metadata: name: podinfo-prod namespace: prod labels: chart: podinfo annotations: flux.weave.works/automated: "true" flux.weave.works/tag.chart-image: semver:~0.4 spec: releaseName: podinfo-prod chart: git: email@example.com:stefanprodan/gitops-helm path: charts/podinfo ref: master values: image: stefanprodan/podinfo:0.4.10 replicaCount: 3
Now if I release a new patch, let's say
0.4.11, Flux will automatically deploy it.
$ cd hack && ./ci-mock.sh -r stefanprodan/podinfo -v 0.4.11 Successfully tagged stefanprodan/podinfo:0.4.11
Managing Kubernetes secrets
In order to store secrets safely in a public Git repo you can use the Bitnami Sealed Secrets controller and encrypt your Kubernetes Secrets into SealedSecrets. The SealedSecret can be decrypted only by the controller running in your cluster.
This is the sealed-secrets controller release:
apiVersion: flux.weave.works/v1beta1 kind: HelmRelease metadata: name: sealed-secrets namespace: adm labels: chart: sealed-secrets spec: releaseName: sealed-secrets git: firstname.lastname@example.org:stefanprodan/gitops-helm path: charts/sealed-secrets ref: master values: image: quay.io/bitnami/sealed-secrets-controller:v0.7.0
Note that this release is not automated, since this is a critical component I prefer to update it manually.
Install the kubeseal CLI:
wget https://github.com/bitnami-labs/sealed-secrets/releases/download/v0.7.0/kubeseal-darwin-amd64 sudo install -m 755 kubeseal-darwin-amd64 /usr/local/bin/kubeseal
At startup, the sealed-secrets controller generates a RSA key and logs the public key. Using kubeseal you can save your public key as
pub-cert.pem, the public key can be safely stored in Git, and can be used to encrypt secrets without direct access to the Kubernetes cluster:
kubeseal --fetch-cert \ --controller-namespace=adm \ --controller-name=sealed-secrets \ > pub-cert.pem
You can generate a Kubernetes secret locally with kubectl and encrypt it with kubeseal:
kubectl -n dev create secret generic basic-auth \ --from-literal=user=admin \ --from-literal=password=admin \ --dry-run \ -o json > basic-auth.json kubeseal --format=yaml --cert=pub-cert.pem < basic-auth.json > basic-auth.yaml
This generates a custom resource of type
SealedSecret that contains the encrypted credentials:
apiVersion: bitnami.com/v1alpha1 kind: SealedSecret metadata: name: basic-auth namespace: adm spec: encryptedData: password: AgAR5nzhX2TkJ....... user: AgAQDO58WniIV3gTk.......
basic-auth.json file and push the
basic-auth.yaml to Git:
rm basic-auth.json mv basic-auth.yaml /releases/dev/ git commit -a -m "Add basic auth credentials to dev namespace" && git push
Flux will apply the sealed secret on your cluster and sealed-secrets controller will then decrypt it into a Kubernetes secret.
To prepare for disaster recovery you should backup the sealed-secrets controller private key with:
kubectl get secret -n adm sealed-secrets-key -o yaml --export > sealed-secrets-key.yaml
To restore from backup after a disaster, replace the newly-created secret and restart the controller:
kubectl replace secret -n adm sealed-secrets-key -f sealed-secrets-key.yaml kubectl delete pod -n adm -l app=sealed-secrets
Flux Helm Integration FAQ
My Helm charts have more than one container image. How can I automate the image tag update for all my containers?
A container image list can have the following format:
container_name_1: image: repo/app1:tag container_name_2: image: quay.io/repo/app2:tag
Here is an example with different deployment automation policies:
apiVersion: flux.weave.works/v1beta1 kind: HelmRelease metadata: name: openfaas namespace: openfaas labels: chart: openfaas annotations: flux.weave.works/automated: "true" flux.weave.works/tag.prometheus: semver:~2.3 flux.weave.works/tag.alertmanager: glob:v0.15.* flux.weave.works/tag.nats: regexp:^0.6.* spec: releaseName: openfaas chart: repository: https://openfaas.github.io/faas-netes/ name: openfaas version: 1.3.3 values: prometheus: image: prom/prometheus:v2.3.1 alertmanager: image: prom/alertmanager:v0.15.0 nats: image: nats-streaming:0.6.0
I'm using SSL between Helm and Tiller. How can I configure Flux to use the certificate?
When installing Flux, you can supply the CA and client-side certificate using the
helmOperator.tls options, more details here.
I've deleted a
HelmRelease file from Git. Why is the Helm release still running on my cluster?
Flux doesn't delete resources, there is an issue opened about this topic on GitHub. In order to delete a Helm release first remove the file from Git and afterwards run:
kubectl -n dev delete hr/podinfo-dev
The Flux Helm operator will receive the delete event and will purge the Helm release.
I've uninstalled Flux and all my Helm releases are gone. Why is that?
HelmRelease CRD deletion, Kubernetes will remove all
HelmRelease CRs triggering a Helm purge for each release created by Flux. To avoid this you have to manually delete the Flux Helm Operator with
kubectl -n flux delete deployment/flux-helm-operator before running
helm delete flux --purge .
I have a dedicated Kubernetes cluster per environment and I want to use the same Git repo for all. How can I do that?
For each cluster create a Git branch in your config repo. When installing Flux set the Git branch using
How can I monitor the CD pipeline and the workloads managed by Flux?
Weave Cloud is a SaaS product by Weaveworks that extends Flux with:
- a UI for all Flux operations, audit trail and alerts for deployments
- a realtime map of your cluster to debug and analyse its state
- full observability and insights into your cluster (hosted Prometheus with 13 months of metrics history)
- instant Flux operations via GitHub webhooks routing
If you have any questions about GitOps or Weave Flux:
- Join the #gitops Kubernetes slack channel.
- Invite yourself to the Weave community slack.
- Ask a question on the #flux slack channel.
- Join the Weave User Group and get invited to online talks, hands-on training and meetups in your area.
Your feedback is always welcome!