Configure settings for the Spring Cloud Config Server component in Azure Container Apps (preview)

  • Article

Spring Cloud Config Server provides a centralized location to make configuration data available to multiple applications. Use the following guidance to learn how to configure and manage your Spring Cloud Config Server 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 spring-cloud-config 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 Spring Cloud Config Server 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 Spring Cloud Config Server 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 Spring Cloud Config Server 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.

The following configuration settings are available on the spring.cloud.config.server.git configuration property.

Name Property path Description
URI repos.{repoName}.uri URI of remote repository.
Username repos.{repoName}.username Username for authentication with remote repository.
Password repos.{repoName}.password Password for authentication with remote repository.
Search paths repos.{repoName}.search-paths Search paths to use within local working copy. By default searches only the root.
Force pull repos.{repoName}.force-pull Flag to indicate that the repository should force pull. If this value is set to true, then discard any local changes and take from remote repository.
Default label repos.{repoName}.default-label The default label used for Git is main. If you don't set default-label and a branch named main doesn't exist, then the config server tries to check out a branch named master. To disable the fallback branch behavior, you can set tryMasterBranch to false.
Try master branch repos.{repoName}.try-master-branch When set to true, the config server by default tries to check out a branch named master.
Skip SSL validation repos.{repoName}.skip-ssl-validation The configuration server's validation of the Git server's SSL certificate can be disabled by setting the git.skipSslValidation property to true.
Clone-on-start 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.
Timeout repos.{repoName}.timeout Timeout (in seconds) for obtaining HTTP or SSH connection (if applicable). Default 5 seconds.
Refresh rate repos.{repoName}.refresh-rate How often the config server fetches updated configuration data from your Git backend.
Private key repos.{repoName}.private-key Valid SSH private key. Must be set if ignore-local-ssh-settings is true and Git URI is SSH format.
Host key repos.{repoName}.host-key Valid SSH host key. Must be set if host-key-algorithm is also set.
Host key algorithm 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.
Strict host key checking repos.{repoName}.strict-host-key-checking true or false. If false, ignore errors with host key.
Repo location repos.{repoName} URI of remote repository.
Repo name patterns repos.{repoName}.pattern The pattern format is a comma-separated list of {application}/{profile} names with wildcards. If {application}/{profile} doesn't match any of the patterns, it uses the default URI defined under.

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 Spring Cloud Config Server 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 Spring Cloud Config Server 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 spring-cloud-config 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 Spring Cloud Config Server 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 spring-cloud-config 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