Java web app containerization and migration to Azure Kubernetes Service

Article
02/09/2024

Caution

This article references CentOS, a Linux distribution that is nearing End Of Life (EOL) status. Please consider your use and planning accordingly. For more information, see the CentOS End Of Life guidance.

In this article, you'll learn how to containerize Java web applications (running on Apache Tomcat) and migrate them to Azure Kubernetes Service (AKS) using the Azure Migrate: App Containerization tool. The containerization process doesn’t require access to your codebase and provides an easy way to containerize existing applications. The tool works by using the running state of the applications on a server to determine the application components and helps you package them in a container image. The containerized application can then be deployed on Azure Kubernetes Service (AKS).

The Azure Migrate: App Containerization tool currently supports -

Containerizing Java Web Apps on Apache Tomcat (on Linux servers) and deploying them on Linux containers on AKS.
Containerizing Java Web Apps on Apache Tomcat (on Linux servers) and deploying them on Linux containers on App Service. Learn more
Containerizing ASP.NET apps and deploying them on Windows containers on AKS. Learn more
Containerizing ASP.NET apps and deploying them on Windows containers on App Service. Learn more

The Azure Migrate: App Containerization tool helps you to -

Discover your application: The tool remotely connects to the application servers running your Java web application (running on Apache Tomcat) and discovers the application components. The tool creates a Dockerfile that can be used to create a container image for the application.
Build the container image: You can inspect and further customize the Dockerfile as per your application requirements and use that to build your application container image. The application container image is pushed to an Azure Container Registry you specify.
Deploy to Azure Kubernetes Service: The tool then generates the Kubernetes resource definition YAML files needed to deploy the containerized application to your Azure Kubernetes Service cluster. You can customize the YAML files and use them to deploy the application on AKS.

Note

The Azure Migrate: App Containerization tool helps you discover specific application types (ASP.NET and Java web apps on Apache Tomcat) and their components on an application server. To discover servers and the inventory of apps, roles, and features running on on-premises machines, use Azure Migrate: Discovery and assessment capability. Learn more

While all applications won't benefit from a straight shift to containers without significant rearchitecting, some of the benefits of moving existing apps to containers without rewriting include:

Improved infrastructure utilization: With containers, multiple applications can share resources and be hosted on the same infrastructure. This can help you consolidate infrastructure and improve utilization.
Simplified management: By hosting your applications on a modern managed platform like AKS and App Service, you can simplify your management practices. You can achieve this by retiring or reducing the infrastructure maintenance and management processes that you'd traditionally perform with owned infrastructure.
Application portability: With increased adoption and standardization of container specification formats and platforms, application portability is no longer a concern.
Adopt modern management with DevOps: Helps you adopt and standardize on modern practices for management and security and transition to DevOps.

In this tutorial, you'll learn how to:

Set up an Azure account.
Install the Azure Migrate: App Containerization tool.
Discover your Java web application.
Build the container image.
Deploy the containerized application on AKS.

Note

Tutorials show you the simplest deployment path for a scenario so that you can quickly set up a proof-of-concept. Tutorials use default options where possible, and don't show all possible settings and paths.

Prerequisites

Before you begin this tutorial, you should:

Requirement	Details
Identify a machine to install the tool	A Windows machine to install and run the Azure Migrate: App Containerization tool. The Windows machine could be a server (Windows Server 2016 or later) or client (Windows 10) operating system, meaning that the tool can run on your desktop as well. The Windows machine running the tool should have network connectivity to the servers/virtual machines hosting the Java web applications to be containerized. Ensure that 6-GB space is available on the Windows machine running the Azure Migrate: App Containerization tool for storing application artifacts. The Windows machine should have internet access, directly or via a proxy.
Application servers	- Enable Secure Shell (SSH) connection on port 22 on the server(s) running the Java application(s) to be containerized.
Java web application	The tool currently supports - Applications running on Tomcat 8 or Tomcat 9. - Application servers on Ubuntu Linux 16.04/18.04/20.04, Debian 7/8, CentOS 6/7, Red Hat Enterprise Linux 5/6/7. - Applications using Java 7 or Java 8. If you have version outside of this, find an image that supports your required versions and modify the dockerfile to replace image The tool currently doesn't support - Applications servers running multiple Tomcat instances

Prepare an Azure user account

If you don't have an Azure subscription, create a free account before you begin.

Once your subscription is set up, you'll need an Azure user account with:

Owner permissions on the Azure subscription
Permissions to register Microsoft Entra apps

If you just created a free Azure account, you're the owner of your subscription. If you're not the subscription owner, work with the owner to assign the permissions as follows:

In the Azure portal, search for "subscriptions", and under Services, select Subscriptions.
In the Subscriptions page, select the subscription in which you want to create an Azure Migrate project.
Select Access control (IAM).
Select Add > Add role assignment to open the Add role assignment page.
Assign the following role. For detailed steps, see Assign Azure roles using the Azure portal.

Setting Value

Role Owner

Assign access to User

Members azmigrateuser (in this example)
Your Azure account also needs permissions to register Microsoft Entra apps.
In Azure portal, navigate to Microsoft Entra ID > Users > User Settings.
In User settings, verify that Microsoft Entra users can register applications (set to Yes by default).
In case the 'App registrations' settings is set to 'No', request the tenant/global admin to assign the required permission. Alternately, the tenant/global admin can assign the Application Developer role to an account to allow the registration of Microsoft Entra App. Learn more.

Setting	Value
Role	Owner
Assign access to	User
Members	azmigrateuser (in this example)

Download and install Azure Migrate: App Containerization tool

Download the Azure Migrate: App Containerization installer on a Windows machine.
Launch PowerShell in administrator mode and change the PowerShell directory to the folder containing the installer.
Run the installation script using the command
```
.\AppContainerizationInstaller.ps1
```

Note

For Windows Server 2022, edit line 135 and remove PowerShell-ISE from the feature list, as it's no longer supported.

Launch the App Containerization tool

Open a browser on any machine that can connect to the Windows machine running the App Containerization tool, and open the tool URL: https://machine name or IP address: 44369.

Alternately, you can open the app from the desktop by selecting the app shortcut.
If you see a warning stating that says your connection isn’t private, click Advanced and choose to proceed to the website. This warning appears as the web interface uses a self-signed TLS/SSL certificate.
At the sign-in screen, use the local administrator account on the machine to sign-in.
Select Java web apps on Tomcat as the type of application you want to containerize.
To specify target Azure service, select Containers on Azure Kubernetes Service.

Complete tool pre-requisites

Accept the license terms, and read the third-party information.
In the tool web app > Set up prerequisites, do the following steps:
- Connectivity: The tool checks that the Windows machine has internet access. If the machine uses a proxy:
  - Click on Set up proxy to specify the proxy address (in the form IP address or FQDN) and listening port.
  - Specify credentials if the proxy needs authentication.
  - Only HTTP proxy is supported.
  - If you've added proxy details or disabled the proxy and/or authentication, click on Save to trigger connectivity check again.
- Install updates: The tool will automatically check for latest updates and install them. You can also manually install the latest version of the tool from here.
- Enable Secure Shell (SSH): The tool will inform you to ensure that Secure Shell (SSH) is enabled on the application servers running the Java web applications to be containerized.

Click Sign in to log in to your Azure account.

You'll need a device code to authenticate with Azure. Clicking on sign in will open a modal with the device code.
Click on Copy code & sign in to copy the device code and open an Azure sign in prompt in a new browser tab. If it doesn't appear, make sure you've disabled the pop-up blocker in the browser.
On the new tab, paste the device code and complete sign in using your Azure account credentials. You can close the browser tab after sign in is complete and return to the App Containerization tool's web interface.
Select the Azure tenant that you want to use.
Specify the Azure subscription that you want to use.

Discover Java web applications

The App Containerization helper tool connects remotely to the application servers using the provided credentials and attempts to discover Java web applications (running on Apache Tomcat) hosted on the application servers.

Specify the IP address/FQDN and the credentials of the server running the Java web application that should be used to remotely connect to the server for application discovery.
- The credentials provided must be for a root account (Linux) on the application server.
- For domain accounts (the user must be an administrator on the application server), prefix the username with the domain name in the format <domain\username>.
- You can run application discovery for upto five servers at a time.
Click Validate to verify that the application server is reachable from the machine running the tool and that the credentials are valid. Upon successful validation, the status column will show the status as Mapped.
Click Continue to start application discovery on the selected application servers.
Upon successful completion of application discovery, you can select the list of applications to containerize.
Use the checkbox to select the applications to containerize.
Specify container name: Specify a name for the target container for each selected application. The container name should be specified as <name:tag> where the tag is used for container image. For example, you can specify the target container name as appname:v1.

Parameterize application configurations

Parameterizing the configuration makes it available as a deployment time parameter. This allows you to configure this setting while deploying the application as opposed to having it hard-coded to a specific value in the container image. For example, this option is useful for parameters like database connection strings.

Click app configurations to review detected configurations.
Select the checkbox to parameterize the detected application configurations.
Click Apply after selecting the configurations to parameterize.

Externalize file system dependencies

You can add other folders that your application uses. Specify if they should be part of the container image or are to be externalized through persistent volumes on Azure file share. Using persistent volumes works great for stateful applications that store state outside the container or have other static content stored on the file system. Learn more

Click Edit under App Folders to review the detected application folders. The detected application folders have been identified as mandatory artifacts needed by the application and will be copied into the container image.
Click Add folders and specify the folder paths to be added.
To add multiple folders to the same volume, provide comma (,) separated values.
Select Persistent Volume as the storage option if you want the folders to be stored outside the container on a Persistent Volume.
Click Save after reviewing the application folders.
Click Continue to proceed to the container image build phase.

Build container image

Select Azure Container Registry: Use the dropdown to select an Azure Container Registry that will be used to build and store the container images for the apps. You can use an existing Azure Container Registry or choose to create a new one using the Create new registry option.
Review the Dockerfile: The Dockerfile needed to build the container images for each selected application are generated at the beginning of the build step. Click Review to review the Dockerfile. You can also add any necessary customizations to the Dockerfile in the review step and save the changes before starting the build process.
Configure Application Insights: You can enable monitoring for your Java apps running on App Service without instrumenting your code. The tool will install the Java standalone agent as part of the container image. Once configured during deployment, the Java agent will automatically collect a multitude of requests, dependencies, logs, and metrics for your application that can be used for monitoring with Application Insights. This option is enabled by default for all Java applications.
Trigger build process: Select the applications to build images for and click Build. Clicking build will start the container image build for each application. The tool keeps monitoring the build status continuously and will let you proceed to the next step upon successful completion of the build.
Track build status: You can also monitor progress of the build step by clicking the Build in Progress link under the status column. The link takes a couple of minutes to be active after you've triggered the build process.
Once the build is completed, click Continue to specify deployment settings.

Deploy the containerized app on AKS

Once the container image is built, the next step is to deploy the application as a container on Azure Kubernetes Service (AKS).

Select the Azure Kubernetes Service Cluster: Specify the AKS cluster that the application should be deployed to.
- The selected AKS cluster must have a Linux node pool.
- The cluster must be configured to allow pulling of images from the Azure Container Registry that was selected to store the images.
  - Run the following command in Azure CLI to attach the AKS cluster to the ACR.
```
az aks update -n <cluster-name> -g <cluster-resource-group> --attach-acr <acr-name>
```
- If you don’t have an AKS cluster or would like to create a new AKS cluster to deploy the application to, you can choose to create on from the tool by clicking Create new AKS cluster.
  - The AKS cluster created using the tool will be created with a Linux node pool. The cluster will be configured to allow it to pull images from the Azure Container Registry that was created earlier (if create new registry option was chosen).
- Click Continue after selecting the AKS cluster.
Specify secret store and monitoring workspace: If you had opted to parameterize application configurations, then specify the secret store to be used for the application. You can choose Azure Key Vault or Kubernetes Secrets for managing your application secrets.
- If you've selected Kubernetes secrets for managing secrets, then click Continue.
- If you'd like to use an Azure Key Vault for managing your application secrets, then specify the Azure Key Vault that you'd want to use.
  - If you don’t have an Azure Key Vault or would like to create a new Key Vault, you can choose to create on from the tool by clicking Create new.
  - The tool will automatically assign the necessary permissions for managing secrets through the Key Vault.
- Monitoring workspace: If you'd selected to enabled monitoring with Application Insights, then specify the Application Insights resource that you'd want to use. This option won't be visible if you had disabled monitoring integration.
  - If you don’t have an Application Insights resource or would like to create a new resource, you can choose to create on from the tool by clicking Create new.
Specify Azure file share: If you had added more folders and selected the Persistent Volume option, then specify the Azure file share that should be used by Azure Migrate: App Containerization tool during the deployment process. The tool will create new directories in this Azure file share to copy over the application folders that are configured for Persistent Volume storage. Once the application deployment is complete, the tool will clean up the Azure file share by deleting the directories it had created.
- If you don't have an Azure file share or would like to create a new Azure file share, you can choose to create on from the tool by clicking Create new Storage Account and file share.
Application deployment configuration: Once you've completed the steps above, you'll need to specify the deployment configuration for the application. Click Configure to customize the deployment for the application. In the configure step you can provide the following customizations:
- Prefix string: Specify a prefix string to use in the name for all resources that are created for the containerized application in the AKS cluster.
- Replica Sets: Specify the number of application instances (pods) that should run inside the containers.
- Load balancer type: Select External if the containerized application should be reachable from public networks.
- Application Configuration: For any application configurations that were parameterized, provide the values to use for the current deployment.
- Storage: For any application folders that were configured for Persistent Volume storage, specify whether the volume should be shared across application instances or should be initialized individually with each instance in the container. By default, all application folders on Persistent Volumes are configured as shared.
- Click Apply to save the deployment configuration.
- Click Continue to deploy the application.
Deploy the application: Once the deployment configuration for the application is saved, the tool will generate the Kubernetes deployment YAML for the application.
- Click Review to review and customize the Kubernetes deployment YAML for the applications.
- Select the application to deploy.
- Click Deploy to start deployments for the selected applications
- Once the application is deployed, you can click the Deployment status column to track the resources that were deployed for the application.

Download generated artifacts

All artifacts that are used to build and deploy the application into AKS, including the Dockerfile and Kubernetes YAML specification files, are stored on the machine running the tool. The artifacts are located at C:\ProgramData\Microsoft Azure Migrate App Containerization.

A single folder is created for each application server. You can view and download all intermediate artifacts used in the containerization process by navigating to this folder. The folder, corresponding to the application server, will be cleaned up at the start of each run of the tool for a particular server.

Troubleshoot issues

To troubleshoot any issues with the tool, you can look at the log files on the Windows machine running the App Containerization tool. Tool log files are located at C:\ProgramData\Microsoft Azure Migrate App Containerization\Logs folder.

Next steps

Containerizing Java web apps on Apache Tomcat (on Linux servers) and deploying them on Linux containers on App Service. Learn more
Containerizing ASP.NET web apps and deploying them on Windows containers on AKS. Learn more
Containerizing ASP.NET web apps and deploying them on Windows containers on Azure App Service. Learn more
What are solutions for running Oracle WebLogic Server on the Azure Kubernetes Service? Learn more
Open Liberty and WebSphere Liberty on AKS. Learn more

Java web app containerization and migration to Azure Kubernetes Service

Prerequisites

Prepare an Azure user account

Download and install Azure Migrate: App Containerization tool