Jenkins X is the self described CI/CD solution for modern cloud applications on Kubernetes.

Jenkins X uses Helm to manage Kubernetes deployments. This short post is about leveraging the dynamism of Helm charts to allow different environment variables per environment and even per pull request.

Prerequisite

You have a cluster running that is managed by Jenkins X. There are plenty of getting started tutorials on the Jenkins X website and since this post is more about how to use Helm with Jenkins X, we won't be covering installation.

Jenkins X

Jenkins X subscribes to the GitOps methodology, which means the Git is used as a single source of truth for continuous delivery. With Jenkins X, Helm charts are kept in your code repository, builds are triggered by PRs or branch merges, and Jenkins X handles deploying to either a preview or an environment based upon your configuration.

It's likely that you would want different environment variables based upon which environment your application is deployed. I'm going to show you how to do this.

Builds

For our contrived use of environment variables, we're going to use a slightly modified version of the Jenkins X Python quickstart application. You can find the finished product on GitHub.

PRs and Staging

For pull requests, we want our app to show the Jenkins branch name as noted in the built-in BRANCH_NAME environment variable. If we merge to master and deploy to staging, we'll just set the branch as master.

For building previews of pull requests, Jenkins X uses a simple Makefile to inject values into a few of the Helm YAML files. We're going to follow this approach, take the BRANCH_NAME variable from Jenkins and use that in our deployment definition.

We're going to add a branchName key under the preview key in the charts/preview/values.yaml file. preview will look like this:

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1preview:
2  image:
3    repository:
4    tag:
5    pullPolicy: IfNotPresent
6  branchName:

Now, in charts/preview/Makefile, we'll grab the BRANCH_NAME environment variable from Jenkins. After creating the two branchName lines, the Makefile will add our new environment variable to our preview values.

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1OS := $(shell uname)
2
3preview:
4ifeq ($(OS),Darwin)
5  sed -i "" -e "s/version:.*/version: $(PREVIEW_VERSION)/" Chart.yaml
6  sed -i "" -e "s/version:.*/version: $(PREVIEW_VERSION)/" ../*/Chart.yaml
7  sed -i "" -e "s/tag:.*/tag: $(PREVIEW_VERSION)/" values.yaml
8  # This is a new line.
9  sed -i "" -e "s/branchName:.*/branchName: $(BRANCH_NAME)/" values.yaml
10else ifeq ($(OS),Linux)
11  sed -i -e "s/version:.*/version: $(PREVIEW_VERSION)/" Chart.yaml
12  sed -i -e "s/version:.*/version: $(PREVIEW_VERSION)/" ../*/Chart.yaml
13  sed -i -e "s|repository:.*|repository: $(DOCKER_REGISTRY)\/duffn\/jx-environment-variables|" values.yaml
14  sed -i -e "s/tag:.*/tag: $(PREVIEW_VERSION)/" values.yaml
15  # This is a new line.
16  sed -i -e "s/branchName:.*/branchName: $(BRANCH_NAME)/" values.yaml
17else
18  echo "platfrom $(OS) not supported to release from"
19  exit -1
20endif
21  echo "  version: $(PREVIEW_VERSION)" >> requirements.yaml
22  jx step helm build

Now, we're going to add an env section at the bottom of charts/jx-environment-variables/values.yaml.

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1env:
2  - name: BRANCH_NAME
3    value: "master"

Finally, in charts/jx-environment-variables/templates/deployment.yaml, we'll utilize the variables that we setup. If our values.yaml contains branchName, we'll display that in our app, otherwise we'll get the env section that we created above.

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1apiVersion: extensions/v1beta1
2kind: Deployment
3metadata:
4  name: {{ template "fullname" . }}
5  labels:
6    draft: {{ default "draft-app" .Values.draft }}
7    chart: "{{ .Chart.Name }}-{{ .Chart.Version | replace "+" "_" }}"
8spec:
9  replicas: {{ .Values.replicaCount }}
10  template:
11    metadata:
12      labels:
13        draft: {{ default "draft-app" .Values.draft }}
14        app: {{ template "fullname" . }}
15{{- if .Values.podAnnotations }}
16      annotations:
17{{ toYaml .Values.podAnnotations | indent 8 }}
18{{- end }}
19    spec:
20      containers:
21      - name: {{ .Chart.Name }}
22        image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
23        imagePullPolicy: {{ .Values.image.pullPolicy }}
24        ports:
25        - containerPort: {{ .Values.service.internalPort }}
26{{/*
27Here's the section we added.
28*/}}
29{{- if .Values.env }}
30        env:
31{{- if .Values.branchName }}
32          - name: BRANCH_NAME
33            value: {{ .Values.branchName | quote }}
34{{- else }}
35{{ toYaml .Values.env | indent 10 }}
36{{- end }}
37{{- end }}
38        resources:
39{{ toYaml .Values.resources | indent 12 }}

When we build a PR, we can see that we'll have PR-XX output by our app and when we build staging, we'll see master. It works!

Production

Okay, but now we want to display something different when we promote our staging image to production. How do we do that since it's going to use exactly the same image and the values.yaml file as well?

Thankfully, you can override values per environment using the production repository that Jenkins X creates for us when we initialize our cluster. Mine happens to be called environment-razorfortune-production. This is the repository that Jenkins X will use when we promote an image to our production environment.

In the env/values.yaml file in this repository, let's add our production variable.

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1jx-environment-variables:
2  env:
3    - name: BRANCH_NAME
4      value: "i am in production!"

Note: You need to add any overriding values underneath a key that is the exact name of your application. Don't let this trip you up!

And now when we promote our image to production, we'll get i am in production!.

Conclusion

This example was a bit contrived, but now you can see some of the power in utilizing Jenkins X for continuous delivery in Kubernetes. Now you have environment specific variables (or anything that you can put in values.yaml for that matter) in Jenkins X. Get to it!