Deploy Spring Boot Application to the Azure Kubernetes Service

Article
08/28/2024

Note

For Spring Boot applications, we recommend using Azure Spring Apps. However, you can still choose to use Azure Kubernetes Service as a destination. For more information, see Choose the right Azure services for your Java applications.

This tutorial walks you through combining Kubernetes and Docker to develop and deploy a Spring Boot application to Microsoft Azure. More specifically, you use Spring Boot for application development, Kubernetes for container deployment, and the Azure Kubernetes Service (AKS) to host your application.

Kubernetes and Docker are open-source solutions that help developers automate the deployment, scaling, and management of their applications running in containers.

Prerequisites

An Azure subscription; if you don't already have an Azure subscription, you can activate your MSDN subscriber benefits or sign up for a free Azure account.
The Azure Command-Line Interface (CLI).
A supported Java Development Kit (JDK). For more information about the JDKs available for use when developing on Azure, see Java support on Azure and Azure Stack.
Apache's Maven build tool (Version 3).
A Git client.
A Docker client.
The ACR Docker credential helper.

Note

Due to the virtualization requirements of this tutorial, you cannot follow the steps in this article on a virtual machine; you must use a physical computer with virtualization features enabled.

Create the Spring Boot on Docker Getting Started web app

The following steps walk you through building a Spring Boot web application and testing it locally.

Open a command-prompt and create a local directory to hold your application, and change to that directory; for example:
```
mkdir C:\SpringBoot
cd C:\SpringBoot
```
-- or --
```
mkdir /users/$USER/SpringBoot
cd /users/$USER/SpringBoot
```
Clone the Spring Boot on Docker Getting Started sample project into the directory.
```
git clone https://github.com/spring-guides/gs-spring-boot-docker.git
```
Change directory to the completed project.
```
cd gs-spring-boot-docker
cd complete
```
Use Maven to build and run the sample app.
```
mvn package spring-boot:run
```
Test the web app by browsing to http://localhost:8080, or with the following curl command:
```
curl http://localhost:8080
```
You should see the following message displayed: Hello Docker World

Create an Azure Container Registry using the Azure CLI

Open a command prompt.
Log in to your Azure account:
```
az login
```
Choose your Azure Subscription:
```
az account set -s <YourSubscriptionID>
```
Create a resource group for the Azure resources used in this tutorial.
```
az group create --name=wingtiptoys-kubernetes --location=eastus
```
Create a private Azure container registry in the resource group. The tutorial pushes the sample app as a Docker image to this registry in later steps. Replace wingtiptoysregistry with a unique name for your registry.
```
az acr create --resource-group wingtiptoys-kubernetes --location eastus \
 --name wingtiptoysregistry --sku Basic
```

Push your app to the container registry via Jib

# set the default name for Azure Container Registry, otherwise you need to specify the name in "az acr login"
az config set defaults.acr=wingtiptoysregistry
az acr login

Open the pom.xml file with a text editor; for example Visual Studio Code.
```
code pom.xml
```

Update the <properties> collection in the pom.xml file with the registry name for your Azure Container Registry and the latest version of jib-maven-plugin.

<properties>
   <!-- Note: If your ACR name contains upper case characters, be sure to convert them to lower case characters. -->
   <docker.image.prefix>wingtiptoysregistry.azurecr.io</docker.image.prefix>
   <jib-maven-plugin.version>2.5.2</jib-maven-plugin.version>
   <java.version>1.8</java.version>
</properties>

Update the <plugins> collection in the pom.xml file so that the <plugin> element contains an entry for the jib-maven-plugin, as shown in the following example. Note that we are using a base image from the Microsoft Container Registry (MCR): mcr.microsoft.com/openjdk/jdk:11-ubuntu, which contains an officially supported JDK for Azure. For other MCR base images with officially supported JDKs, see Install the Microsoft Build of OpenJDK..
```
<plugin>
  <artifactId>jib-maven-plugin</artifactId>
  <groupId>com.google.cloud.tools</groupId>
  <version>${jib-maven-plugin.version}</version>
  <configuration>
     <from>
         <image>mcr.microsoft.com/openjdk/jdk:11-ubuntu</image>
     </from>
     <to>
         <image>${docker.image.prefix}/gs-spring-boot-docker</image>
     </to>
  </configuration>
</plugin>
```
Navigate to the completed project directory for your Spring Boot application and run the following command to build the image and push the image to the registry:
```
az acr login && mvn compile jib:build
```

Note

Due to the security concern of Azure Cli and Azure Container Registry, the credential created by az acr login is valid for 1 hour. If you see a 401 Unauthorized error, you can run the az acr login --name <your registry name> command again to reauthenticate. If you see a Read timed out error, you can try increasing timeouts with mvn -Djib.httpTimeout=7200000 jib:dockerBuild, or -Djib.httpTimeout=0 for an infinite timeout.

Create a Kubernetes Cluster on AKS using the Azure CLI

Create a Kubernetes cluster in Azure Kubernetes Service. The following command creates a kubernetes cluster in the wingtiptoys-kubernetes resource group, with wingtiptoys-akscluster as the cluster name, with Azure Container Registry (ACR) wingtiptoysregistry attached, and wingtiptoys-kubernetes as the DNS prefix:
```
az aks create --resource-group=wingtiptoys-kubernetes --name=wingtiptoys-akscluster \
 --attach-acr wingtiptoysregistry \
 --dns-name-prefix=wingtiptoys-kubernetes --generate-ssh-keys
```
This command may take a while to complete.
Install kubectl using the Azure CLI. Linux users may have to prefix this command with sudo since it deploys the Kubernetes CLI to /usr/local/bin.
```
az aks install-cli
```
Download the cluster configuration information so you can manage your cluster from the Kubernetes web interface and kubectl.
```
az aks get-credentials --resource-group=wingtiptoys-kubernetes --name=wingtiptoys-akscluster
```

Deploy the image to your Kubernetes cluster

This tutorial deploys the app using kubectl, then allows you to explore the deployment through the Kubernetes web interface.

Deploy with kubectl

Open a command prompt.
Run your container in the Kubernetes cluster by using the kubectl run command. Give a service name for your app in Kubernetes and the full image name. For example:
```
kubectl run gs-spring-boot-docker --image=wingtiptoysregistry.azurecr.io/gs-spring-boot-docker:latest
```
In this command:
- The container name gs-spring-boot-docker is specified immediately after the run command
- The --image parameter specifies the combined login server and image name as wingtiptoysregistry.azurecr.io/gs-spring-boot-docker:latest
Expose your Kubernetes cluster externally by using the kubectl expose command. Specify your service name, the public-facing TCP port used to access the app, and the internal target port your app listens on. For example:
```
kubectl expose pod gs-spring-boot-docker --type=LoadBalancer --port=80 --target-port=8080
```
In this command:
- The container name gs-spring-boot-docker is specified immediately after the expose pod command.
- The --type parameter specifies that the cluster uses load balancer.
- The --port parameter specifies the public-facing TCP port of 80. You access the app on this port.
- The --target-port parameter specifies the internal TCP port of 8080. The load balancer forwards requests to your app on this port.
Once the app is deployed to the cluster, query the external IP address and open it in your web browser:
```
kubectl get services -o=jsonpath='{.items[*].status.loadBalancer.ingress[0].ip}'
```

Deploy with the Kubernetes resource view

Select Add from any of the resource views (Namespace, Workloads, Services and ingresses, Storage, or Configuration).

Paste in the following YAML:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: gs-spring-boot-docker
spec:
  replicas: 1
  selector:
    matchLabels:
      app: gs-spring-boot-docker
  template:
    metadata:
      labels:
        app: gs-spring-boot-docker
    spec:
      containers:
      - name: gs-spring-boot-docker
        image: wingtiptoysregistry.azurecr.io/gs-spring-boot-docker:latest

Select Add at the bottom of the YAML editor to deploy the application.

After deploying the Deployment, just like above, select Add at the bottom of the YAML editor to deploy Service using the following YAML:
```
apiVersion: v1
kind: Service
metadata:
  name: gs-spring-boot-docker
spec:
  type: LoadBalancer
  ports:
  - port: 80
    targetPort: 8080
  selector:
    app: gs-spring-boot-docker
```
Once the YAML file is added, the resource viewer shows your Spring Boot application. The external service includes a linked external IP address so you can easily view the application in your browser.
Select External IP. You'll then see your Spring Boot application running on Azure.