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Deploy applications with Helm

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Applies to: AKS on Azure Stack HCI 22H2, AKS on Windows Server

Helm is an open-source packaging tool that helps you install and manage the lifecycle of Kubernetes applications. Similar to Linux package managers, such as APT and Yum, Helm manages Kubernetes charts, which are packages of pre-configured Kubernetes resources.

This article describes how to use Helm to package and deploy applications on AKS when you're using Azure Kubernetes Service enabled by Azure Arc.

Before you begin

Verify that you have the following requirements set up:

This article uses an ASP.NET Core application as an example. You can download the sample application from this GitHub repository.

Since the application is deployed to Kubernetes, the following example is a simple Dockerfile for the project:

FROM mcr.microsoft.com/dotnet/aspnet:5.0-alpine AS base
WORKDIR /app
EXPOSE 80
EXPOSE 443

FROM mcr.microsoft.com/dotnet/sdk:5.0-alpine AS build
WORKDIR /src
COPY ["MyMicroservice.csproj", "./"]
RUN dotnet restore "MyMicroservice.csproj"
COPY . .
WORKDIR "/src/."
RUN dotnet build "MyMicroservice.csproj" -c Release -o /app/build

FROM build AS publish
RUN dotnet publish "MyMicroservice.csproj" -c Release -o /app/publish

FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "MyMicroservice.dll"]

Build and push the sample application to a container registry

Navigate to the application folder and use the Dockerfile to build and push an image using the following command:

docker build -f Dockerfile -t acr.azurecr.io/mymicroservice:0.1.0 .

Note

The period (.) at the end of the command sets the location of the Dockerfile (in this case, the current directory).

This command creates the image mymicroservice:0.1.0 on the local machine. To verify that the image was successfully created, run docker images to confirm:

REPOSITORY              TAG     IMAGE ID       CREATED            SIZE  
acr.azurecr.io/mymicroservice 0.1.0   5be713db571b   About a minute ago 107MB
....

Next, push your image to a container registry, such as DockerHub or Azure Container Registry. In this example, the container image is pushed to Azure Container Registry. For more information, see Pull images from an ACR to a Kubernetes cluster:

docker push acr.azurecr.io/mymicroservice:0.1.0

Create your Helm chart

Now that the sample application is ready, the next step is to generate a Helm chart using the helm create command, as follows:

helm create mymicroserviceapp

Update mymicroserviceapp/values.yaml, as follows:

  • Change image.repository to acr.azurecr.io/mymicroservice.
  • Change service.type to NodePort.

For example:

# Default values for webfrontend.
# This is a YAML-formatted file.
# Declare variables to be passed into your templates.

replicaCount: 1

image:
  repository: acr.azurecr.io/mymicroservice
  pullPolicy: IfNotPresent
...
service:
  type: NodePort
  port: 80
...

Navigate to the mymicroserviceapp/templates/deployment.yaml file to configure health checks. Kubernetes uses health checks to manage your application deployments. Replace the path to both liveness and readiness probes with path: /weatherforecast, as shown in the following example:

...
 livenessProbe:
    httpGet:
      path: /weatherforecast
      port: http
    initialDelaySeconds: 0
    periodSeconds: 10
    timeoutSeconds: 1
    failureThreshold: 3
 readinessProbe:
    httpGet:
      path: /weatherforecast
      port: http
    successThreshold: 3
...

Deploy your Helm chart to Kubernetes

Starting from the charts\mymicroserviceapp directory in the solution directory, run the following command:

helm upgrade --install mymicroserviceapp . --namespace=local --set mymicroserviceapp.image.tag="0.1.0"

This command creates (or upgrades) an existing release using the name mymicroserviceapp in the local namespace in the Kubernetes cluster, and produces output similar to this example:

Release "mymicroserviceapp" does not exist. Installing it now.
NAME: mymicroserviceapp
LAST DEPLOYED: Fri Apr  2 08:47:24 2021
NAMESPACE: local
STATUS: deployed
REVISION: 1
NOTES:
1. Get the application URL by running these commands:
  export NODE_PORT=$(kubectl get --namespace local -o jsonpath="{.spec.ports[0].nodePort}" services mymicroserviceapp)
  export NODE_IP=$(kubectl get nodes --namespace local -o jsonpath="{.items[0].status.addresses[0].address}")
  echo http://$NODE_IP:$NODE_PORT

After you deploy the Helm chart, you can check that the resources were correctly deployed by running kubectl get all -n local.

The output from running the command is:

NAME                                     READY   STATUS    RESTARTS   AGE
pod/mymicroserviceapp-7849f949df-fwgbn   1/1     Running   0          101s

NAME                        TYPE       CLUSTER-IP     EXTERNAL-IP   PORT(S)        AGE
service/mymicroserviceapp   NodePort   10.100.149.1   <none>        80:30501/TCP   101s

NAME                                READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/mymicroserviceapp   1/1     1            1           101s

NAME                                           DESIRED   CURRENT   READY   AGE
replicaset.apps/mymicroserviceapp-7849f949df   1         1         1       101s

Test your deployment

The application deploys with a service and a node port, so you can call the API from outside the cluster. To make this call, send a request to: http://$NODE_IP:$NODE_PORT:

curl http://10.193.2.103:30501/WeatherForeCast/

StatusCode        : 200
StatusDescription : OK
Content           : [{"date":"2021-04-03T15:51:04.795216+00:00","temperatureC":45,"temperatureF":112,"summary":"Balmy"},{"date":"2021-04-04T15:51:04.
                    7952176+00:00","temperatureC":23,"temperatureF":73,"summary":"Cool"},{"...
RawContent        : HTTP/1.1 200 OK
                    Transfer-Encoding: chunked
                    Content-Type: application/json; charset=utf-8
                    Date: Fri, 02 Apr 2021 15:51:04 GMT
                    Server: Kestrel

                    [{"date":"2021-04-03T15:51:04.795216+00:00","tempera...
Forms             : {}
Headers           : {[Transfer-Encoding, chunked], [Content-Type, application/json; charset=utf-8], [Date, Fri, 02 Apr 2021 15:51:04 GMT], [Server,
                    Kestrel]}
Images            : {}
InputFields       : {}
Links             : {}
ParsedHtml        : mshtml.HTMLDocumentClass
RawContentLength  : 494

Clean up the cluster

The final step is to clean up the cluster. To delete Kubernetes deployment resources, run the following command:

helm uninstall mymicroserviceapp -n local

You should get output similar to the following example:

release "mymicroserviceapp" uninstalled

Next steps