Tutorial: Create a highly available Eureka server component cluster in Azure Container Apps

In this tutorial, you find out how to create a Eureka service that's designed to remain operational in the face of failures and high demand. Building a highly available Eureka service helps ensure the service registry that you use for Azure Container Apps is always available to clients regardless of demand.

Achieving high availability status for Eureka includes linking multiple Eureka server instances together so they form a cluster. The cluster provides resources so that if one Eureka server fails, the other services remain available for requests.

In this tutorial, you:

Prerequisites

• An Azure account with an active subscription. If you don't already have one, you can create one for free.
• The Azure CLI.

Considerations

When you run managed Java components in Container Apps, be aware of the following details:

Set up initial resources

Use the following steps to create some resources that you need for your Eureka service cluster.

1. Create variables that hold application configuration values.

   export LOCATION=eastus
   export RESOURCE_GROUP=my-services-resource-group
   export ENVIRONMENT=my-environment
   export EUREKA_COMPONENT_FIRST=eureka01
   export EUREKA_COMPONENT_SECOND=eureka02
   export APP_NAME=sample-service-eureka-client
   export IMAGE="mcr.microsoft.com/javacomponents/samples/sample-service-eureka-client:latest"
   

2. Use the Azure CLI to sign in to Azure.

   az login
   

3. Create a resource group.

   az group create --name $RESOURCE_GROUP --location $LOCATION
   

4. Create your Container Apps environment.

   az containerapp env create \
       --name $ENVIRONMENT \
       --resource-group $RESOURCE_GROUP \
       --location $LOCATION
   

Create servers for a cluster

Create two Eureka Server for Spring components.

az containerapp env java-component eureka-server-for-spring create \
    --environment $ENVIRONMENT \
    --resource-group $RESOURCE_GROUP \
    --name $EUREKA_COMPONENT_FIRST

az containerapp env java-component eureka-server-for-spring create \
    --environment $ENVIRONMENT \
    --resource-group $RESOURCE_GROUP \
    --name $EUREKA_COMPONENT_SECOND

Bind components together to form a cluster

For the Eureka servers to work in a high-availability configuration, they need to be linked together as a cluster.

1. Bind the first Eureka server to the second.

   az containerapp env java-component eureka-server-for-spring update \
       --environment $ENVIRONMENT \
       --resource-group $RESOURCE_GROUP \
       --name $EUREKA_COMPONENT_FIRST \
       --bind $EUREKA_COMPONENT_SECOND
   

2. Bind the second Eureka server to the first.

   az containerapp env java-component eureka-server-for-spring update \
       --environment $ENVIRONMENT \
       --resource-group $RESOURCE_GROUP \
       --name $EUREKA_COMPONENT_SECOND \
       --bind $EUREKA_COMPONENT_FIRST
   

Deploy and bind the application

With the server components linked together, you can create the container app and bind it to the two Eureka components.

1. Create the container app.

   az containerapp create \
       --name $APP_NAME \
       --resource-group $RESOURCE_GROUP \
       --environment $ENVIRONMENT \
       --image $IMAGE \
       --min-replicas 1 \
       --max-replicas 1 \
       --ingress external \
       --target-port 8080
   

2. Bind the container app to the first Eureka server component.

   az containerapp update \
       --name $APP_NAME \
       --resource-group $RESOURCE_GROUP \
       --bind $EUREKA_COMPONENT_FIRST 
   

3. Bind the container app to the second Eureka server component.

   az containerapp update \
       --name $APP_NAME \
       --resource-group $RESOURCE_GROUP \
       --bind $EUREKA_COMPONENT_SECOND
   

View the dashboard

Create and assign a custom role

1. Create the custom role definition. Before you run this command, replace the placeholder in the AssignableScopes value with your subscription ID.

   az role definition create --role-definition '{
       "Name": "Java Component Dashboard Access",
       "IsCustom": true,
       "Description": "Can access managed Java Component dashboards in managed environments",
       "Actions": [
           "Microsoft.App/managedEnvironments/write"
       ],
       "AssignableScopes": ["/subscriptions/<SUBSCRIPTION_ID>"]
   }'
   

2. Get the resource ID of the Container Apps environment.

   export ENVIRONMENT_ID=$(az containerapp env show \
       --name $ENVIRONMENT --resource-group $RESOURCE_GROUP \
       --query id \
       --output tsv)
   

3. Assign the custom role to your account for the Container Apps environment resource. Before you run this command, replace the placeholder in the assignee value with your user object ID or service principal ID.

   az role assignment create \
       --assignee <USER_OR_SERVICE_PRINCIPAL_ID> \
       --role "Java Component Dashboard Access" \
       --scope $ENVIRONMENT_ID
   

Get the dashboard URL

Get the URL of the Eureka Server for Spring dashboard.

az containerapp env java-component eureka-server-for-spring show \
    --environment $ENVIRONMENT \
    --resource-group $RESOURCE_GROUP \
    --name $EUREKA_COMPONENT_FIRST \
    --query properties.ingress.fqdn \
    --output tsv

This command returns the URL you can use to access the Eureka Server for Spring dashboard. Through the dashboard, you can verify that the Eureka server setup consists of two replicas.

Clean up resources

The resources created in this tutorial affect your Azure bill. If you aren't going to use these services in the long term, run the following command to remove everything created in this tutorial.

az group delete --resource-group $RESOURCE_GROUP

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