Tutorial: Connect to a managed Eureka Server for Spring in Azure Container Apps

Article
09/13/2024

Eureka Server for Spring is a service registry that allows microservices to register themselves and discover other services. Available as an Azure Container Apps component, you can bind your container app to a Eureka Server for Spring for automatic registration with the Eureka server.

In this tutorial, you learn to:

Create a Eureka Server for Spring Java component
Bind your container app to Eureka Server for Spring Java component

Important

This tutorial uses services that can affect your Azure bill. If you decide to follow along step-by-step, make sure you delete the resources featured in this article to avoid unexpected billing.

Prerequisites

To complete this project, you need the following items:

Requirement	Instructions
Azure account	An active subscription is required. If you don't have one, you can create one for free.
Azure CLI	Install the Azure CLI.

Considerations

When running in Eureka Server for Spring in Azure Container Apps, be aware of the following details:

Item	Explanation
Scope	The Eureka Server for Spring component runs in the same environment as the connected container app.
Scaling	The Eureka Server for Spring can't scale. The scaling properties `minReplicas` and `maxReplicas` are both set to `1`.
Resources	The container resource allocation for Eureka Server for Spring is fixed. The number of the CPU cores is 0.5, and the memory size is 1Gi.
Pricing	The Eureka Server for Spring billing falls under consumption-based pricing. Resources consumed by managed Java components are billed at the active/idle rates. You can delete components that are no longer in use to stop billing.
Binding	Container apps connect to a Eureka Server for Spring component via a binding. The bindings inject configurations into container app environment variables. Once a binding is established, the container app can read the configuration values from environment variables and connect to the Eureka Server for Spring.

Setup

Before you begin to work with the Eureka Server for Spring, you first need to create the required resources.

Azure CLI
Azure portal

Execute the following commands to create your resource group, container apps environment.

Create variables to support your application configuration. These values are provided for you for the purposes of this lesson.

export LOCATION=chinanorth3
export RESOURCE_GROUP=my-services-resource-group
export ENVIRONMENT=my-environment
export EUREKA_COMPONENT_NAME=eureka
export APP_NAME=my-eureka-client
export IMAGE="mcr.microsoft.com/javacomponents/samples/sample-service-eureka-client:latest"

Variable	Description
`LOCATION`	The Azure region location where you create your container app and Java component.
`ENVIRONMENT`	The Azure Container Apps environment name for your demo application.
`RESOURCE_GROUP`	The Azure resource group name for your demo application.
`EUREKA_COMPONENT_NAME`	The name of the Java component created for your container app. In this case, you create a Eureka Server for Spring Java component.
`IMAGE`	The container image used in your container app.

az cloud set -n AzureChinaCloud
az login
# az cloud set -n AzureCloud   //means return to Public Azure.

Create a resource group.

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

Create your container apps environment.

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

Use the following steps to create each of the resources necessary to create a container app.

Search for Container Apps in the Azure portal and select Create.
Enter the following values to Basics tab.

Property	Value
Subscription	Select your Azure subscription.
Resource group	Select Create new link to create a new resource group named my-resource-group.
Container app name	Enter my-eureka-client.
Deployment source	Select Container image.
Region	Select the region nearest you.
Container Apps environment	Select the Create new link to create a new environment.

In the Create Container Apps environment window, enter the following values.

Property	Value
Environment name	Enter my-environment.
Zone redundancy	Select Disabled.

Select the Create button, and then select the Container tab.

In Container tab, enter the following values.

Property	Value
Name	Enter my-eureka-client.
Image source	Select Docker Hub or other registries.
Image type	Select Public.
Registry login server	Enter mcr.microsoft.com.
Image and tag	Enter javacomponents/samples/sample-service-eureka-client:latest.

Select the Ingress tab.

In Ingress tab, enter the following and leave the rest of the form with their default values.

Property	Value
Ingress	Select Enabled.
Ingress traffic	Select Accept traffic from anywhere.
Ingress type	Select HTTP.
Target port	Enter 8080.

Select Review + create.

Once the validation checks pass, select Create to create your container app.

Create the Eureka Server for Spring Java component

Azure CLI
Azure portal

Now that you have an existing environment, you can create your container app and bind it to a Java component instance of Eureka Server for Spring.

Create the Eureka Server for Spring Java component.

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

Optional: Update the Eureka Server for Spring Java component configuration.

az containerapp env java-component eureka-server-for-spring update \
  --environment $ENVIRONMENT \
  --resource-group $RESOURCE_GROUP \
  --name $EUREKA_COMPONENT_NAME 
  --configuration eureka.server.renewal-percent-threshold=0.85 eureka.server.eviction-interval-timer-in-ms=10000

Now that you have an existing environment and eureka client container app, you can create a Java component instance of Eureka Server for Spring.

Go to your container app's environment in the portal.
From the left menu, under Services category, select Services.
Select + Configure drop down, and select Java component.
In the Configure Java component panel, enter the following values.

Property	Value
Java component type	Select Eureka Server for Spring.
Java component name	Enter eureka.

Select Next.
On the Review tab, select Configure.

Bind your container app to the Eureka Server for Spring Java component

Azure CLI
Azure portal

Create the container app and bind to the Eureka Server for Spring.

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 \
  --bind $EUREKA_COMPONENT_NAME \
  --query properties.configuration.ingress.fqdn

Copy the URL of your app to a text editor so you can use it in a coming step.

Return to the container app in the portal and copy the URL of your app to a text editor so you can use it in a coming step.

Navigate to the /allRegistrationStatus route to view all applications registered with the Eureka Server for Spring.

The binding injects several configurations into the application as environment variables, primarily the eureka.client.service-url.defaultZone property. This property indicates the internal endpoint of the Eureka Server Java component.

The binding also injects the following properties:

"eureka.client.register-with-eureka":    "true"
"eureka.client.fetch-registry":          "true"
"eureka.instance.prefer-ip-address":     "true"

The eureka.client.register-with-eureka property is set to true to enforce registration with the Eureka server. This registration overwrites the local setting in application.properties, from the config server and so on. If you want to set it to false, you can overwrite it by setting an environment variable in your container app.

The eureka.instance.prefer-ip-address is set to true due to the specific DNS resolution rule in the container app environment. Don't modify this value so you don't break the binding.

(Optional) Unbind your container app from the Eureka Server for Spring Java component

Azure CLI
Azure portal

To remove a binding from a container app, use the --unbind option.

  az containerapp update \
    --name $APP_NAME \
    --unbind $JAVA_COMPONENT_NAME \
    --resource-group $RESOURCE_GROUP

View the application through a dashboard

Important

To view the dashboard, you need to have at least the Microsoft.App/managedEnvironments/write role assigned to your account on the managed environment resource. You can either explicitly assign Owner or Contributor role on the resource or follow the steps to create a custom role definition and assign it to your account.

Create the custom role definition.

az role definition create --role-definition '{
    "Name": "<YOUR_ROLE_NAME>",
    "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.

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 -o tsv)

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 "<ROLE_NAME>" \
  --scope $ENVIRONMENT_ID
```
Note

<USER_OR_SERVICE_PRINCIPAL_ID> usually should be the identity that you use to access Azure Portal. <ROLE_NAME> is the name you assigned in step 1.
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_NAME \
  --query properties.ingress.fqdn -o tsv
```
This command returns the URL you can use to access the Eureka Server for Spring dashboard. Through the dashboard, your container app is also to you as shown in the following screenshot.

Optional: Integrate the Eureka Server for Spring and Admin for Spring Java components

If you want to integrate the Eureka Server for Spring and the Admin for Spring Java components, see Integrate the managed Admin for Spring with Eureka Server for Spring.

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

Next steps

Configure Eureka Server for Spring settings

Integrate the managed Admin for Spring with Eureka Server for Spring