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

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

• 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 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. After 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

Execute the following commands to create your resource group and Container Apps environment.

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

   export LOCATION=eastus
   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 repository 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.

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
   

Azure portal

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

1. Search for Container Apps in the Azure portal and select Create.

2. 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.

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

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

   Select Create, then select the Container tab.

4. In the 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.

5. 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.

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

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

1. 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
   

2. 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.

Azure portal

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.

1. Go to your container app's environment in the portal.

2. On the navigation menu, under Services category, select Services.

3. Select the Configure drop down, and select Java component.

4. 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.

5. In the Git repositories section, select Add and then 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 then select Add.

6. Select Next.

7. On the Review tab, select Configure.

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

Azure CLI

1. 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.

2. 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.

Azure portal

1. Go to your container app environment in the portal.

2. On the navigation menu, under the Services category, select Services.

3. From the list, select configserver.

4. Under bindings, select the App name drop-down and then select my-config-client.

5. Select the Review tab.

6. Select Configure.

7. Return to your 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.

After 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 repository 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

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

Azure portal

1. Go to your container app environment in the portal.

2. On the navigation menu, under Services category, select Services.

3. From the list, select configserver.

4. Under Bindings, find the line for my-config-client, then select Delete.

5. Select Next.

6. Select the Review tab.

7. Select Configure.

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

Configuration options

The az containerapp update command uses the --configuration parameter to control how the Config Server for Spring is configured. You can use multiple parameters at once as long as they're separated by a space. For more information, see Spring Cloud Config Server.

The following table describes the different Git backend configuration values available:

Name	Description
spring.cloud.config.server.git.uri spring.cloud.config.server.git.repos.{repoName}.uri	URI of remote repository.
spring.cloud.config.server.git.username spring.cloud.config.server.git.repos.{repoName}.username	Username for authentication with remote repository.
spring.cloud.config.server.git.password spring.cloud.config.server.git.repos.{repoName}.password	Password for authentication with remote repository.
spring.cloud.config.server.git.search-paths spring.cloud.config.server.git.repos.{repoName}.search-paths	Search paths to use within local working copy. By default, searches only the root.
spring.cloud.config.server.git.force-pull spring.cloud.config.server.git.repos.{repoName}.force-pull	Flag to indicate that the repository should force pull. If true, discard any local changes and take from the remote repository.
spring.cloud.config.server.git.default-label spring.cloud.config.server.git.repos.{repoName}.default-label	The default label used for Git is main. If you don't set spring.cloud.config.server.git.default-label and a branch named main doesn't exist, the config server by default also tries to checkout a branch named master. If you'd like to disable the fallback branch behavior, you can set spring.cloud.config.server.git.tryMasterBranch to false.
spring.cloud.config.server.git.try-master-branch spring.cloud.config.server.git.repos.{repoName}.try-master-branch	The config server by default tries to checkout a branch named master.
spring.cloud.config.server.git.skip-ssl-validation spring.cloud.config.server.git.repos.{repoName}.skip-ssl-validation	You can disable the configuration server's validation of the Git server's TLS/SSL certificate by setting the git.skipSslValidation property to true.
spring.cloud.config.server.git.clone-on-start spring.cloud.config.server.git.repos.{repoName}.clone-on-start	Flag to indicate that the repository should be cloned on startup, not on demand. Generally leads to slower startup but faster first query.
spring.cloud.config.server.git.timeout spring.cloud.config.server.git.repos.{repoName}.timeout	Timeout in seconds for obtaining HTTP or SSH connection, if applicable. The default value is 5 seconds.
spring.cloud.config.server.git.refresh-rate spring.cloud.config.server.git.repos.{repoName}.refresh-rate	How often the config server fetches updated configuration data from your Git backend.
spring.cloud.config.server.git.private-key spring.cloud.config.server.git.repos.{repoName}.private-key	Valid SSH private key. Must be set if ignore-local-ssh-settings is true and the Git URI is in SSH format.
spring.cloud.config.server.git.host-key spring.cloud.config.server.git.repos.{repoName}.host-key	Valid SSH host key. Must be set if host-key-algorithm is also set.
spring.cloud.config.server.git.host-key-algorithm spring.cloud.config.server.git.repos.{repoName}.host-key-algorithm	One of ssh-dss, ssh-rsa, ssh-ed25519, ecdsa-sha2-nistp256, ecdsa-sha2-nistp384, or ecdsa-sha2-nistp521. Must be set if host-key is also set.
spring.cloud.config.server.git.strict-host-key-checking spring.cloud.config.server.git.repos.{repoName}.strict-host-key-checking	true or false. If false, ignore errors with host key.
spring.cloud.config.server.git.repos.{repoName}	URI of remote repository.
spring.cloud.config.server.git.repos.{repoName}.pattern	The pattern format is a comma-separated list of {application}/{profile} names with wildcards. If {application}/{profile} does not match any of the patterns, it uses the default URI defined under.

The following list describes common configurations:

• Logging related configurations:

  • logging.level.*
  • logging.group.*
  • Any other configurations under the logging.* namespace should be forbidden - for example, writing log files by using logging.file should be forbidden.

• spring.cloud.config.server.overrides

  • Extra map for a property source to be sent to all clients unconditionally.

• spring.cloud.config.override-none

  • You can change the priority of all overrides in the client to be more like default values, letting applications supply their own values in environment variables or System properties, by setting the spring.cloud.config.override-none=true flag - the default is false - in the remote repository.

• spring.cloud.config.allow-override

  • If you enable config first bootstrap, you can allow client applications to override configuration from the config server by placing two properties within the applications configuration coming from the config server.

• spring.cloud.config.server.health.*

  • You can configure the Health Indicator to check more applications along with custom profiles and custom labels.

• spring.cloud.config.server.accept-empty

  • You can set spring.cloud.config.server.accept-empty to false so that the server returns an HTTP 404 status if the application isn't found. By default, this flag is set to true.

• Encryption and decryption (symmetric):

  • encrypt.key
    • Convenient when you use a symmetric key because it's a single property value to configure.
  • spring.cloud.config.server.encrypt.enabled
    • Set this property to false to disable server-side decryption.

Refresh

Services that consume properties need to know about a change before it happens. The default notification method for Config Server for Spring involves manually triggering the refresh event, such as a refresh by call https://<YOUR_CONFIG_CLIENT_HOST_NAME>/actuator/refresh, which might not be feasible if there are many app instances.

Instead, you can automatically refresh values from Config Server by letting the config client poll for changes based on a refresh internal. Use the following steps to automatically refresh values from Config Server:

1. Register a scheduled task to refresh the context in a given interval, as shown in the following example:

   @Configuration
   @AutoConfigureAfter({RefreshAutoConfiguration.class, RefreshEndpointAutoConfiguration.class})
   @EnableScheduling
   public class ConfigClientAutoRefreshConfiguration implements SchedulingConfigurer {
       @Value("${spring.cloud.config.refresh-interval:60}")
       private long refreshInterval;
       @Value("${spring.cloud.config.auto-refresh:false}")
       private boolean autoRefresh;
       private final RefreshEndpoint refreshEndpoint;
       public ConfigClientAutoRefreshConfiguration(RefreshEndpoint refreshEndpoint) {
           this.refreshEndpoint = refreshEndpoint;
       }
       @Override
       public void configureTasks(ScheduledTaskRegistrar scheduledTaskRegistrar) {
           if (autoRefresh) {
               // set minimal refresh interval to 5 seconds
               refreshInterval = Math.max(refreshInterval, 5);
               scheduledTaskRegistrar.addFixedRateTask(refreshEndpoint::refresh,  Duration.ofSeconds(refreshInterval));
           }
       }
   }
   

2. Enable autorefresh and set the appropriate refresh interval in the application.yml file. In the following example, the client polls for a configuration change every 60 seconds, which is the minimum value you can set for a refresh interval.

   By default, autorefresh is set to false and refresh-interval is set to 60 seconds.

   spring:
       cloud:
           config:
           auto-refresh: true
           refresh-interval: 60
   management:
       endpoints:
           web:
           exposure:
               include:
               - refresh
   

3. Add @RefreshScope in your code. In the following example, the variable connectTimeout is automatically refreshed every 60 seconds:

   @RestController
   @RefreshScope
   public class HelloController {
       @Value("${timeout:4000}")
       private String connectTimeout;
   }
   

Encryption and decryption with a symmetric key

Server-side decryption

By default, server-side encryption is enabled. Use the following steps to enable decryption in your application:

1. Add the encrypted property in your .properties file in your Git repository.

   Your file should resemble the following example:

   message={cipher}f43e3df3862ab196a4b367624a7d9b581e1c543610da353fbdd2477d60fb282f
   

2. Update the Config Server for Spring Java component to use the Git repository that has the encrypted property and set the encryption key.

   Before you run the following command, replace placeholders surrounded by <> with your values.

   az containerapp env java-component config-server-for-spring update \
       --environment <ENVIRONMENT_NAME> \
       --resource-group <RESOURCE_GROUP> \
       --name <JAVA_COMPONENT_NAME> \
       --configuration spring.cloud.config.server.git.uri=<URI> encrypt.key=randomKey
   

Client-side decryption

You can use client side decryption of properties by following the steps:

1. Add the encrypted property in your .properties file in your Git repository.

2. Update the Config Server for Spring Java component to use the Git repository that has the encrypted property and disable server-side decryption.

   Before you run the following command, replace placeholders surrounded by <> with your values.

   az containerapp env java-component config-server-for-spring update \
       --environment <ENVIRONMENT_NAME> \
       --resource-group <RESOURCE_GROUP> \
       --name <JAVA_COMPONENT_NAME> \
       --configuration spring.cloud.config.server.git.uri=<URI> spring.cloud.config.server.encrypt.enabled=false
   

3. In your client app, add the decryption key ENCRYPT_KEY=randomKey as an environment variable.

   Alternatively, if you include spring-cloud-starter-bootstrap on the classpath, or set spring.cloud.bootstrap.enabled=true as a system property, set encrypt.key in bootstrap.properties.

   Before you run the following command, replace placeholders surrounded by <> with your values.

   az containerapp update \
       --name <APP_NAME> \
       --resource-group <RESOURCE_GROUP> \
       --set-env-vars "ENCRYPT_KEY=randomKey"
   

   encrypt:
     key: somerandomkey