App Test Go App

This is a simple web application in go lang.

The main propose of this app is give support to devops labs like deploy apps in kubernetes, best pratices in contarnization, helming apps and others

Building the app

After that you make your Dockerfile, run:

docker build --tag app-test:<your_tag_version> .

Pushing the docker image to Docker Registry

You can have others container registry, here we are using Docker Hub Registry. To push the docker image to Docker Hub Registry, run:

docker login -u <your_dockerhub_username> && \
docker tag app-test:<your_tag_version> igoritosousa22/app-test:<tag_version> && \
docker push igoritosousa22/app-test:<tag_version>

Deploy on Kubernetes

To deploy this app on Kubernetes, first create a manifest deploy passing the URL container registry on the image entry:

#path: infra/app-test/yaml/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: go-app-test
  labels:
    app: go-app-test
spec:
  replicas: 1
  selector:
    matchLabels:
      app: go-app-test
  template:
    metadata:
      labels:
        app: go-app-test
    spec:
      containers:
        - name: go-app-test
          image: docker.io/igoritosousa22/app-test:1.0.0
          imagePullPolicy: Always
          ports:
            - containerPort: 8080
              protocol: TCP

Create a Helm Chart for app-test

First, you must create the app-test files and directories. Then, run:

helm create app-test

So, the directory app-test will be created with some other files, Let's see one of them:

• charts - where the dependencies stored
• templates - is where the templates for Deployments, Services, ConfigMap, etc are stored.
• .helmignore - files that will bem ignore in process. Like dockerignore or gitignore file.
• Chart.yaml - is where are defined informations about Chart
• values.yaml - defines the values that will be used by templates for yor chart.

Let's run the chart:

helm install app-test go/app-test/

If all works, you must see the output like these:

NAME: app-test
LAST DEPLOYED: Sun Mar 20 16:17:01 2022
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: None

Using values.yaml

The helm charts allow you customize templates to apply your deployments. So, we will pass the values of our deployment in the values.yaml file. Firts edit the template/deployment.yaml with the placeholder values: {{.Value}}

apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{.Values.name}}
  labels:
    app: {{.Values.name}}
spec:
  replicas: {{.Values.deployment.replicas}}
  selector:
    matchLabels:
      app: {{.Values.name}}
  template:
    metadata:
      labels:
        app: {{.Values.name}}
    spec:
      containers:
        - name: {{.Values.name}}
          image: {{.Values.deployment.image}}:{{.Values.deployment.tag}}
          imagePullPolicy: Always
          ports:
            - containerPort: {{.Values.deployment.containerPort}}
              protocol: TCP

So, define the deployment values in the values.yaml:

name: app-test
deployment:
  replicas: 2
  image: docker.io/igoritosousa22/app-test
  tag: 2.0.0
  containerPort: 8080

To see what will be deployed, run this command:

helm template app-test go/app-test/ --debug

Apply the release running the command above

helm install app-test go/app-test/

And, If all it works, you should see something like these:

NAME: app-test
LAST DEPLOYED: Sun Mar 20 16:40:56 2022
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: None

You can verify if the deployment is running on cluster:

$ kubectl get pods 

NAME                        READY   STATUS    RESTARTS   AGE
app-test-6b5d567b89-gsl6j   1/1     Running   0          14m
app-test-6b5d567b89-xzhwf   1/1     Running   0          14m

Upgrade Chart

So, Let's create a service to expose our deployment on templates/service.yaml:

apiVersion: v1
kind: Service
metadata:
  name: svc-{{.Values.name}}
spec:
  ports:
    - name: http
      port: {{.Values.service.port}}
  selector:
    app: {{.Values.name}}

Then, run:

helm template app-test go/app-test/ --debug

If the output works fine and don't show any errors, upgrade your release

helm upgrade app-test go/app-test/

Now you should see that que value of REVISION change:

NAME: app-test
LAST DEPLOYED: Sun Mar 20 17:05:21 2022
NAMESPACE: default
STATUS: deployed
REVISION: 2
TEST SUITE: None

Let's see if the service was created in the cluster:

$ kubectl get svc
NAME           TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)   AGE
svc-app-test   ClusterIP   172.20.190.114   <none>        80/TCP    2m1s

Expose the service to test locally the app-test

kubectl port-forward svc/svc-app-test 8080:8080

Test the app-test with a HTTP request

curl -v http://localhost:8080/v2

(...)
< Content-Type: text/plain; charset=utf-8
< 
* Connection #0 to host localhost left intact
This apps works on  - Version 2!

To clean-up the release, just run:

helm uninstall app-test go/app-test/

References

https://medium.com/geekculture/helm-in-kubernetes-part-2-how-to-create-a-simple-helm-chart-af899fc2741d