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

In this tutorial, you learn to create a Eureka service designed to remain operational in the face of failures and high demand. Building a highly available Eureka service ensures the service registry is always available to clients regardless of demand.

Achieving high availability status for Eureka includes linking multiple Eureka server instances together forming 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 can create one for free.
• Azure CLI.

Considerations

When running managed Java components in Azure Container Apps, be aware of the following details:

Setup

Use the following steps to create 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. Sign in to Azure with the Azure CLI.

   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 a cluster

Next, create two Eureka server instances and link them together as a cluster.

1. 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

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

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 binding 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 dashboards

1. Create the custom role definition.

   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>"]
   }'
   

   Make sure to replace placeholder in between the <> brackets in the AssignableScopes value with your subscription ID.

2. Assign the custom role to your account on managed environment resource.

   Get the resource ID of the managed environment.

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

3. Assign the role to your account.

   Before running this command, replace the placeholder in between the <> brackets with your user or service principal ID.

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

4. 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 have an effect on your Azure bill. If you aren't going to use these services long-term, run the following command to remove everything created in this tutorial.

az group delete --resource-group $RESOURCE_GROUP

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