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

Article
09/13/2024

Config Server for Spring provides a centralized location to make configuration data available to multiple applications. In this article, you learn to connect an app hosted in Azure Container Apps to a Java Config Server for Spring instance.

The Config Server for Spring Java component uses a GitHub repository as the source for configuration settings. Configuration values are made available to your container app via a binding between the component and your container app. As values change in the configuration server, they automatically flow to your application, all without requiring you to recompile or redeploy your application.

In this tutorial, you learn to:

Create a Config Server for Spring Java component
Bind the Config Server for Spring to your container app
Observe configuration values before and after connecting the config server to your application
Encrypt and decrypt configuration values with a symmetric key

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 Config Server for Spring in Azure Container Apps, be aware of the following details:

Item	Explanation
Scope	The Config Server for Spring runs in the same environment as the connected container app.
Scaling	To maintain a single source of truth, the Config Server for Spring doesn't scale. The scaling properties `minReplicas` and `maxReplicas` are both set to `1`.
Resources	The container resource allocation for Config Server for Spring is fixed, the number of the CPU cores is 0.5, and the memory size is 1Gi.
Pricing	The Config 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	The container app connects to a Config Server for Spring via a binding. The binding injects configurations into container app environment variables. Once a binding is established, the container app can read configuration values from environment variables.

Setup

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

Azure CLI
Azure portal

Execute the following commands to create your resource group and 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 JAVA_COMPONENT_NAME=configserver
export APP_NAME=my-config-client
export IMAGE="mcr.microsoft.com/javacomponents/samples/sample-service-config-client:latest"
export URI="https://github.com/Azure-Samples/azure-spring-cloud-config-java-aca.git"

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.
`JAVA_COMPONENT_NAME`	The name of the Java component created for your container app. In this case, you create a Config Server for Spring Java component.
`IMAGE`	The container image used in your container app.
`URI`	You can replace the URI with your git repo url, if it's private, add the related authentication configurations such as `spring.cloud.config.server.git.username` and `spring.cloud.config.server.git.password`.

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-config-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.

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

In Container tab, enter the following values.

Property	Value
Name	Enter my-config-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-config-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.

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

This environment is used to host both the Config Server for Spring java component and your container app.

Create the Config Server for Spring Java component

Now that you have a Container Apps environment, you can create your container app and bind it to a Config Server for Spring java component. When you bind your container app, configuration values automatically synchronize from the Config Server component to your application.

Azure CLI
Azure portal

Create the Config Server for Spring Java component.

az containerapp env java-component config-server-for-spring create \
  --environment $ENVIRONMENT \
  --resource-group $RESOURCE_GROUP \
  --name $JAVA_COMPONENT_NAME \
  --min-replicas 1 \
  --max-replicas 1 \
  --configuration spring.cloud.config.server.git.uri=$URI

Update the Config Server for Spring Java component.

az containerapp env java-component config-server-for-spring update \
  --environment $ENVIRONMENT \
  --resource-group $RESOURCE_GROUP \
  --name $JAVA_COMPONENT_NAME \
  --min-replicas 2 \
  --max-replicas 2 \
  --configuration spring.cloud.config.server.git.uri=$URI spring.cloud.config.server.git.refresh-rate=60

Here, you're telling the component where to find the repository that holds your configuration information via the uri property. The refresh-rate property tells Container Apps how often to check for changes in your git repository.

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

Java component name Enter configserver.
In the Git repositories section, select the + Add button and enter the following values.

Property Value

Type Select HTTP.

URI Enter https://github.com/Azure-Samples/azure-spring-cloud-config-java-aca.git.

Leave the rest of the fields with the default values and select Add.
Select Next.
On the Review tab, select Configure.

Property	Value
Java component type	Select Config Server for Spring.
Java component name	Enter configserver.

Property	Value
Type	Select HTTP.
URI	Enter https://github.com/Azure-Samples/azure-spring-cloud-config-java-aca.git.

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

Azure CLI
Azure portal

Create the container app that consumes configuration data.
```
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 \
  --query properties.configuration.ingress.fqdn
```
This command returns the URL of your container app that consumes configuration data. Copy the URL to a text editor so you can use it in a coming step.

If you visit your app in a browser, the connectTimeout value returned is the default value of 0.
Bind to the Config Server for Spring.

Now that the container app and Config Server are created, you bind them together with the update command to your container app.
```
az containerapp update \
  --name $APP_NAME \
  --resource-group $RESOURCE_GROUP \
  --bind $JAVA_COMPONENT_NAME
```
The --bind $JAVA_COMPONENT_NAME parameter creates the link between your container app and the configuration component.

Once the container app and the Config Server component are bound together, configuration changes are automatically synchronized to the container app.

When you visit the app's URL again, the value of connectTimeout is now 10000. This value comes from the git repo set in the $URI variable originally set as the source of the configuration component. Specifically, this value is drawn from the connectionTimeout property in the repo's application.yml file.

The bind request injects configuration setting into the application as environment variables. These values are now available to the application code to use when fetching configuration settings from the config server.

In this case, the following environment variables are available to the application:

SPRING_CLOUD_CONFIG_URI=http://[JAVA_COMPONENT_INTERNAL_FQDN]:80
SPRING_CLOUD_CONFIG_COMPONENT_URI=http://[JAVA_COMPONENT_INTERNAL_FQDN]:80
SPRING_CONFIG_IMPORT=optional:configserver:$SPRING_CLOUD_CONFIG_URI

If you want to customize your own SPRING_CONFIG_IMPORT, you can refer to the environment variable SPRING_CLOUD_CONFIG_COMPONENT_URI, for example, you can override by command line arguments, like Java -Dspring.config.import=optional:configserver:${SPRING_CLOUD_CONFIG_COMPONENT_URI}?fail-fast=true.

You can also remove a binding from your application.

(Optional) Unbind your container app from the Config 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

When you visit the app's URL again, the value of connectTimeout changes to back to 0.

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

Customize Config Server for Spring settings