Quickstart: Debug and iterate on Kubernetes with Visual Studio Code and Java - Azure Dev Spaces
In this quickstart, you set up Azure Dev Spaces with a managed Kubernetes cluster, and use a Java app in Visual Studio Code to iteratively develop and debug code in containers. Azure Dev Spaces lets you debug and test all the components of your application in Azure Kubernetes Service (AKS) with minimal development machine setup.
- An Azure account with an active subscription. Create an account for free.
- Java Development Kit (JDK) 1.8.0+.
- Maven 3.5.0+.
- Visual Studio Code.
- The Azure Dev Spaces and Java Debugger for Azure Dev Spaces extensions for Visual Studio Code.
- Azure CLI.
Create an Azure Kubernetes Service cluster
You need to create an AKS cluster in a supported region. The following commands create a resource group called MyResourceGroup and an AKS cluster called MyAKS.
az group create --name MyResourceGroup --location eastus az aks create -g MyResourceGroup -n MyAKS --location eastus --generate-ssh-keys
Enable Azure Dev Spaces on your AKS cluster
use-dev-spaces command to enable Dev Spaces on your AKS cluster and follow the prompts. The following command enables Dev Spaces on the MyAKS cluster in the MyResourceGroup group and creates a default dev space.
use-dev-spaces command will also install the Azure Dev Spaces CLI if its not already installed. You can't install the Azure Dev Spaces CLI in the Azure Cloud Shell.
az aks use-dev-spaces -g MyResourceGroup -n MyAKS
'An Azure Dev Spaces Controller' will be created that targets resource 'MyAKS' in resource group 'MyResourceGroup'. Continue? (y/N): y Creating and selecting Azure Dev Spaces Controller 'MyAKS' in resource group 'MyResourceGroup' that targets resource 'MyAKS' in resource group 'MyResourceGroup'...2m 24s Select a dev space or Kubernetes namespace to use as a dev space.  default Type a number or a new name: 1 Kubernetes namespace 'default' will be configured as a dev space. This will enable Azure Dev Spaces instrumentation for new workloads in the namespace. Continue? (Y/n): Y Configuring and selecting dev space 'default'...3s Managed Kubernetes cluster 'MyAKS' in resource group 'MyResourceGroup' is ready for development in dev space 'default'. Type `azds prep` to prepare a source directory for use with Azure Dev Spaces and `azds up` to run.
Get sample application code
In this article, you use the Azure Dev Spaces sample application to demonstrate using Azure Dev Spaces.
Clone the application from GitHub.
git clone https://github.com/Azure/dev-spaces
Prepare the sample application in Visual Studio Code
Open Visual Studio Code, select File then Open, navigate to the dev-spaces/samples/java/getting-started/webfrontend directory, and select Open.
You now have the webfrontend project open in Visual Studio Code. To run the application in your dev space, generate the Docker and Helm chart assets using the Azure Dev Spaces extension in the Command Palette.
To open the Command Palette in Visual Studio Code, select View then Command Palette. Begin typing
Azure Dev Spaces and select Azure Dev Spaces: Prepare configuration files for Azure Dev Spaces.
When Visual Studio Code also prompts you to configure your base images, exposed port and public endpoint, choose
Azul Zulu OpenJDK for Azure (Free LTS) for the base image,
8080 for the exposed port, and
Yes to enable a public endpoint.
This command prepares your project to run in Azure Dev Spaces by generating a Dockerfile and Helm chart. It also generates a .vscode directory with debugging configuration at the root of your project.
The Dockerfile and Helm chart for your project is used by Azure Dev Spaces to build and run your code, but you can modify these files if you want to change how the project is built and run.
Build and run code in Kubernetes from Visual Studio Code
Select the Debug icon on the left and select Launch Java Program (AZDS) at the top.
This command builds and runs your service in Azure Dev Spaces. The Terminal window at the bottom shows the build output and URLs for your service running Azure Dev Spaces. The Debug Console shows the log output.
If you don't see any Azure Dev Spaces commands in the Command Palette, make sure you have installed the Visual Studio Code extension for Azure Dev Spaces. Also verify you opened the dev-spaces/samples/java/getting-started/webfrontend directory in Visual Studio Code.
You can see the service running by opening the public URL.
Select Debug then Stop Debugging to stop the debugger.
To deploy an updated version of your service, you can update any file in your project and rerun Launch Java Program (AZDS). For example:
If your application is still running, select Debug then Stop Debugging to stop it.
return "Hello from webfrontend in Azure!";
Save your changes.
Rerun Launch Java Program (AZDS).
Navigate to your running service and observe your changes.
Select Debug then Stop Debugging to stop your application.
Setting and using breakpoints for debugging
Start your service using Launch Java Program (AZDS). This also runs your service in debugging mode.
Navigate back to the Explorer view by selecting View then Explorer. Open src/main/java/com/ms/sample/webfrontend/Application.java and click somewhere on line 19 to put your cursor there. To set a breakpoint press F9 or select Debug then Toggle Breakpoint.
Open your service in a browser and notice no message is displayed. Return to Visual Studio Code and observe line 19 is highlighted. The breakpoint you set has paused the service at line 19. To resume the service, press F5 or select Debug then Continue. Return to your browser and notice the message is now displayed.
While running your service in Kubernetes with a debugger attached, you have full access to debug information such as the call stack, local variables, and exception information.
Remove the breakpoint by putting your cursor on line 19 in src/main/java/com/ms/sample/webfrontend/Application.java and pressing F9.
Update code from Visual Studio Code
While the service is running in debugging mode, update line 19 in src/main/java/com/ms/sample/webfrontend/Application.java. For example:
return "Hello from webfrontend in Azure while debugging!";
Save the file. Select Debug then Restart Debugging or in the Debug toolbar, select the Restart Debugging button.
Open your service in a browser and notice your updated message is displayed.
Instead of rebuilding and redeploying a new container image each time code edits are made, Azure Dev Spaces incrementally recompiles code within the existing container to provide a faster edit/debug loop.
Clean up your Azure resources
az group delete --name MyResourceGroup --yes --no-wait
Learn more about how Azure Dev Spaces works.