Configure settings for the Config Server for Spring component in Azure Container Apps

Config Server for Spring provides a centralized location to make configuration data available to multiple applications. Use the following guidance to learn how to configure and manage your Config Server for Spring component.

Show

You can view the details of an individual component by name using the show command.

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

az containerapp env java-component config-server-for-spring show \
  --environment <ENVIRONMENT_NAME> \
  --resource-group <RESOURCE_GROUP> \
  --name <JAVA_COMPONENT_NAME>

List

You can list all registered Java components using the list command.

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

az containerapp env java-component list \
  --environment <ENVIRONMENT_NAME> \
  --resource-group <RESOURCE_GROUP>

Bind

Use the --bind parameter of the update command to create a connection between the Config Server for Spring component and your container app.

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

az containerapp update \
  --name <CONTAINER_APP_NAME> \
  --resource-group <RESOURCE_GROUP> \
  --bind <JAVA_COMPONENT_NAME>

Unbind

To break the connection between your container app and the Config Server for Spring component, use the --unbind parameter of the update command.

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

az containerapp update \
  --name <CONTAINER_APP_NAME> \
  --unbind <JAVA_COMPONENT_NAME> \
  --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. You can find more details in Spring Cloud Config Server docs.

The following table lists the different configuration values available.

Git backend configurations

Common configurations

• logging related configurations

  • logging.level.*
  • logging.group.*
  • Any other configurations under 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 is not found. By default, this flag is set to true.

• Encryption and decryption (symmetric)

  • encrypt.key
    • It is convenient to use a symmetric key since it is a single property value to configure.
  • spring.cloud.config.server.encrypt.enabled
    • You can set this to false, to disable server-side decryption.

Refresh

Services that consume properties need to know about the change before it happens. The default notification method for Config Server for Spring involves manually triggering the refresh event, such as refresh by call https://<YOUR_CONFIG_CLIENT_HOST_NAME>/actuator/refresh, which may 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.

   For example, 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
   

Next steps