Use Application Configuration Service for Tanzu

This article applies to: ❌ Basic/Standard ✔️ Enterprise

This article shows you how to use Application Configuration Service for VMware Tanzu with the Azure Spring Apps Enterprise plan.

Application Configuration Service for VMware Tanzu is one of the commercial VMware Tanzu components. It enables the management of Kubernetes-native ConfigMap resources that are populated from properties defined in one or more Git repositories.

With Application Configuration Service, you have a central place to manage external properties for applications across all environments. To understand the differences from Spring Cloud Config Server in the Basic and Standard plans, see the Use Application Configuration Service for external configuration section of Migrate an Azure Spring Apps Basic or Standard plan instance to the Enterprise plan.

Application Configuration Service is offered in two versions: Gen1 and Gen2. The Gen1 version mainly serves existing customers for backward compatibility purposes, and is supported only until April 30, 2024. New service instances should use Gen2. The Gen2 version uses flux as the backend to communicate with Git repositories, and provides better performance compared to Gen1.

The following table shows the subcomponent relationships:

The following table shows some benchmark data for your reference. However, the Git repository size is a key factor with significant impact on the performance data. We recommend that you store only the necessary configuration files in the Git repository in order to keep it small.

Gen2 also provides more security verifications when you connect to a remote Git repository. Gen2 requires a secure connection if you're using HTTPS, and verifies the correct host key and host algorithm when using an SSH connection.

You can choose the version of Application Configuration Service when you create an Azure Spring Apps Enterprise service instance. The default version is Gen1. You can also upgrade to Gen2 after the instance is created, but downgrade isn't supported. The upgrade is zero downtime, but we still recommend that you to test in a staging environment before moving to a production environment.

Prerequisites

• An already provisioned Azure Spring Apps Enterprise plan instance with Application Configuration Service enabled. For more information, see Quickstart: Build and deploy apps to Azure Spring Apps using the Enterprise plan.

Manage Application Configuration Service settings

Application Configuration Service supports Azure DevOps, GitHub, GitLab, and Bitbucket for storing your configuration files.

To manage the service settings, open the Settings section. In this section, you can configure the following key aspects:

• Generation: Upgrade the service generation.
• Refresh Interval: Adjust the frequency at which the service checks for updates from Git repositories.
• Repositories: Add new entries, or modify existing ones. This function enables you to control which repositories the service monitors use to pull data.

If your current service generation is Gen1, you can upgrade to Gen2 for better performance. For more information, see the Upgrade from Gen1 to Gen2 section.

The Refresh Interval specifies the frequency (in seconds) for checking updates in the repository. The minimum value is 0, which disables automatic refresh. For optimal performance, set this interval to a minimum value of 60 seconds.

The following table describes the properties for each repository entry:

Pattern

Configuration is pulled from Git backends using what you define in a pattern. A pattern is a combination of {application}/{profile} as described in the following guidelines.

• {application} - The name of an application whose configuration you're retrieving. The value application is considered the default application and includes configuration information shared across multiple applications. Any other value refers to a specific application and includes properties for both the specific application and shared properties for the default application.
• {profile} - Optional. The name of a profile whose properties you can retrieve. An empty value, or the value default, includes properties that are shared across profiles. Non-default values include properties for the specified profile and properties for the default profile.

Authentication

The following screenshot shows the three types of repository authentication supported by Application Configuration Service.

The following list describes the three authentication types:

• Public repository.

  You don't need any extra authentication configuration when you use a public repository. Select Public in the Authentication form.

  The following table shows the configurable property you can use to set up a public Git repository:

  Property	Required?	Description
  CA certificate	No	Required only when a self-signed cert is used for the Git repo URL.

• Private repository with basic authentication.

  The following table shows the configurable properties you can use to set up a private Git repository with basic authentication:

  Property	Required?	Description
  username	Yes	The username used to access the repository.
  password	Yes	The password used to access the repository.
  CA certificate	No	Required only when a self-signed cert is used for the Git repo URL.

• Private repository with SSH authentication.

  The following table shows the configurable properties you can use to set up a private Git repository with SSH:

  Property	Required?	Description
  Private key	Yes	The private key that identifies the Git user. Passphrase-encrypted private keys aren't supported.
  Host key	No for Gen1 Yes for Gen2	The host key of the Git server. If you connect to the server via Git on the command line, the host key is in your .ssh/known_hosts file. Don't include the algorithm prefix, because it's specified in Host key algorithm.
  Host key algorithm	No for Gen1 Yes for Gen2	The algorithm for hostKey: one of ssh-dss, ssh-rsa, ecdsa-sha2-nistp256, ecdsa-sha2-nistp384, and ecdsa-sha2-nistp521. (Required if supplying Host key).
  Strict host key checking	No	Optional value that indicates whether the backend should be ignored if it encounters an error when using the provided Host key. Valid values are true and false. The default value is true.

To validate access to the target URI, select Validate. After validation completes successfully, select Apply to update the configuration settings.

Upgrade from Gen1 to Gen2

Application Configuration Service Gen2 provides better performance compared to Gen1, especially when you have a large number of configuration files. We recommend using Gen2, especially because Gen1 is being retired soon. The upgrade from Gen1 to Gen2 is zero downtime, but we still recommend that you test in a staging environment before moving to a production environment.

Gen2 requires more configuration properties than Gen1 when using SSH authentication. You need to update the configuration properties in your application to make it work with Gen2. The following table shows the required properties for Gen2 when using SSH authentication:

Use the following steps to upgrade from Gen1 to Gen2:

1. In the Azure portal, navigate to the Application Configuration Service page for your Azure Spring Apps service instance.

2. Select the Settings section and then select Gen2 in the Generation dropdown menu.

   

3. Select Validate to validate access to the target URI. After validation completes successfully, select Apply to update the configuration settings.

   

Polyglot support

The Application Configuration Service works seamlessly with Spring Boot applications. The properties generated by the service are imported as external configurations by Spring Boot and injected into the beans. You don't need to write extra code. You can consume the values by using the @Value annotation, accessed through Spring's Environment abstraction, or you can bind them to structured objects by using the @ConfigurationProperties annotation.

The Application Configuration Service also supports polyglot apps like dotNET, Go, Python, and so on. To access config files that you specify to load during polyglot app deployment in the apps, try to access a file path that you can retrieve through an environment variable with a name such as AZURE_SPRING_APPS_CONFIG_FILE_PATH. You can access all your intended config files under that path. To access the property values in the config files, use the existing read/write file libraries for your app.

Refresh strategies

When you modify and commit your configurations in a Git repository, several steps are involved before these changes are reflected in your applications. This process, though automated, involves the following distinct stages and components, each with its own timing and behavior:

• Polling by Application Configuration Service: The Application Configuration Service regularly polls the backend Git repositories to detect any changes. This polling occurs at a set frequency, defined by the refresh interval. When a change is detected, Application Configuration Service updates the Kubernetes ConfigMap.
• ConfigMap update and interaction with kubelet cache: In Azure Spring Apps, this ConfigMap is mounted as a data volume to the relevant application. However, there's a natural delay in this process due to the frequency at which the kubelet refreshes its cache to recognize changes in ConfigMap.
• Application reads updated configuration: Your application running in the Azure Spring Apps environment can access the updated configuration values. The existing beans in the Spring Context aren't automatically refreshed to use the updated configurations.

These stages are summarized in the following diagram:

You can adjust the polling refresh interval of the Application Configuration Service to align with your specific needs. To apply the updated configurations in your application, a restart or refresh action is necessary.

In Spring applications, properties are held or referenced as beans within the Spring Context. To load new configurations, consider using the following methods:

• Restart the application. Restarting the application always loads the new configuration.

• Call the /actuator/refresh endpoint exposed on the config client via the Spring Actuator.

  To use this method, add the following dependency to your configuration client's pom.xml file.

  <dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-actuator</artifactId>
  </dependency>
  

  You can also enable the actuator endpoint by adding the following configuration:

  management.endpoints.web.exposure.include=refresh, bus-refresh, beans, env
  

  After you reload the property sources by calling the /actuator/refresh endpoint, the attributes bound with @Value in the beans having the annotation @RefreshScope are refreshed.

  @Service
  @Getter @Setter
  @RefreshScope
  public class MyService {
     @Value
     private Boolean activated;
  }
  

  Use curl with the application endpoint to refresh the new configuration, as shown in the following example:

  curl -X POST http://{app-endpoint}/actuator/refresh
  

• Use FileSystemWatcher to watch the file change and refresh the context on demand. FileSystemWatcher is a class shipped with spring-boot-devtools that watches specific directories for file changes, or you can use another utility with similar function. The previous option requires users to initiate the refresh actively, while the latter can monitor for file changes and automatically invoke the refresh upon detecting updates. You can retrieve the file path by using the environment variable AZURE_SPRING_APPS_CONFIG_FILE_PATH, as mentioned in the Polyglot support section.

Configure Application Configuration Service settings

az spring application-configuration-service git repo add \
    --name <entry-name> \
    --patterns <patterns> \
    --uri <git-backend-uri> \
    --label <git-branch-name>

Configure the TLS certificate to access the Git backend with a self-signed certificate for Gen2

This step is optional. If you use a self-signed certificate for the Git backend, you must configure the TLS certificate to access the Git backend.

You need to upload the certificate to Azure Spring Apps first. For more information, see the Import a certificate section of Use TLS/SSL certificates in your application in Azure Spring Apps.

az spring application-configuration-service git repo add \
    --name <entry-name> \
    --patterns <patterns> \
    --uri <git-backend-uri> \
    --label <git-branch-name> \
    --ca-cert-name <ca-certificate-name>

Use Application Configuration Service with applications

When you use Application Configuration Service with a Git back end and use the centralized configurations, you must bind the app to Application Configuration Service.

az spring application-configuration-service bind --app <app-name>
az spring app deploy \
    --name <app-name> \
    --artifact-path <path-to-your-JAR-file> \
    --config-file-pattern <config-file-pattern>

Bind an app to the Application Configuration Service

You can now choose to bind your application to the Application Configuration Service when creating a new app.

az spring app create \ 
    --resource-group <resource-group> \ 
    --service <service-name> \ 
    --name <app-name> \ 
    --bind-application-configuration-service 

Enable/disable Application Configuration Service after service creation

You can enable and disable Application Configuration Service after service creation using the Azure portal or the Azure CLI. Before disabling Application Configuration Service, you're required to unbind all of your apps from it.

az spring application-configuration-service create \
    --resource-group <resource-group-name> \
    --service <Azure-Spring-Apps-service-instance-name>

az spring application-configuration-service delete \
    --resource-group <resource-group-name> \
    --service <Azure-Spring-Apps-service-instance-name>

Examine configuration file in ConfigMap

The following section shows you how to examine the content of the configuration file pulled by Application Configuration Service from upstream Git repositories in the related Kubernetes ConfigMap. For more information, see the Refresh strategies section of this article.

Assign an Azure role

First, you must have the Azure role Azure Spring Apps Application Configuration Service Config File Pattern Reader Role assigned to you.

az role assignment create \
    --role "Azure Spring Apps Application Configuration Service Config File Pattern Reader Role" \
    --scope "<service-instance-resource-id>" \
    --assignee "<your-identity>"

Examine configuration file with the Azure CLI

Use the following command to view the content of the configuration file by Pattern:

az spring application-configuration-service config show \
    --resource-group <resource-group-name> \
    --service <Azure-Spring-Apps-instance-name> \
    --config-file-pattern <pattern>

This command produces JSON output similar to the following example:

{
  "configurationFiles": {
    "application.properties": [
      "example.property.application.name: example-service",
      "example.property.cloud: Azure"
    ]
  },
  "metadata": {
    "gitRevisions": "[{\"url\":\"{gitRepoUrl}\",\"revision\":\"{revisionInfo}\"}]"
  }
}

You can also use this command with the --export-path {/path/to/target/folder} parameter to export the configuration file to the specified folder. It supports both relative paths and absolute paths. If you don't specify the path, the command uses the path of the current directory by default.

Examine configuration file in the app

After you bind the app to the Application Configuration Service and set the Pattern for the app deployment, as described in the Use Application Configuration Service with applications section of this article, the ConfigMap containing the configuration file for the pattern should be mounted to the application container. Use the following steps to check the configuration files in each instance of the app deployment:

1. Connect to one of the application instances. For more information, see Connect to an app instance for troubleshooting.

2. Use the echo $AZURE_SPRING_APPS_CONFIG_FILE_PATH command to find the folders containing the configuration files. A list of locations shows up separated by commas, as shown in the following example:

     $ echo $AZURE_SPRING_APPS_CONFIG_FILE_PATH
     /etc/azure-spring-cloud/configmap/acs-default-payment-default-e9d46,/etc/azure-spring-cloud/configmap/acs-default-catalog-default-616f4
   

3. Check the content of the configuration file using commands such as cat.

Check logs

The following sections show you how to view application logs by using either the Azure CLI or the Azure portal.

Use real-time log streaming

You can stream logs in real time with the Azure CLI. For more information, see Stream Azure Spring Apps managed component logs in real time. The following examples show how you can use Azure CLI commands to continuously stream new logs for application-configuration-service and flux-source-controller subcomponents.

Use the following command to stream logs for application-configuration-service:

az spring component logs \
    --resource-group <resource-group-name> \
    --service <Azure-Spring-Apps-instance-name> \
    --name application-configuration-service \
    --all-instances \
    --follow

Use the following command to stream logs for flux-source-controller:

az spring component logs \
    --resource-group <resource-group-name> \
    --service <Azure-Spring-Apps-instance-name> \
    --name flux-source-controller \
    --all-instances \
    --follow

Use Log Analytics

The following sections show you how to turn on and view System Logs using Log Analytics.

Diagnostic settings for Log Analytics

You must turn on System Logs and send the logs to your Log Analytics instance before you query the logs for Application Configuration Service. To enable System Logs in the Azure portal, use the following steps:

1. Open your Azure Spring Apps instance.

2. In the navigation pane, select Diagnostics settings.

3. Select Add diagnostic setting or select Edit setting for an existing setting.

4. In the Logs section, select the System Logs category.

5. In the Destination details section, select Send to Log Analytics workspace and then select your workspace.

6. Select Save to update the setting.

Check logs in Log Analytics

To check the logs of application-configuration-service and flux-source-controller using the Azure portal, use the following steps:

1. Make sure you turned on System Logs. For more information, see the Diagnostic settings for Log Analytics section.

2. Open your Azure Spring Apps instance.

3. In the navigation menu, select Logs and then select Overview.

4. Use the following sample queries in the query edit pane. Adjust the time range then select Run to search for logs.

   • To view the logs for application-configuration-service, use the following query:

     AppPlatformSystemLogs
     | where LogType in ("ApplicationConfigurationService")
     | project TimeGenerated , ServiceName , LogType, Log , _ResourceId
     | limit 100
     

     

   • To view the logs for flux-source-controller, use the following query:

     AppPlatformSystemLogs
     | where LogType in ("Flux")
     | project TimeGenerated , ServiceName , LogType, Log , _ResourceId
     | limit 100
     

     

Examine Git revisions of the configuration files

You can find the Git revision of the configuration file of the Pattern in the logs of Application Configuration Service. The following example log indicates that the configuration file for the payment/default pattern is pulled with example-commit-id from the main branch of the https://github.com/Azure-Samples/acme-fitness-store-config repository. You can learn how to query logs in the Check logs section.

Applied ConfigMap ({config-map-name}) for content (payment/default) from Git repositories https://github.com/Azure-Samples/acme-fitness-store-config@main@sha1:{example-commit-id}

You can also find the Git revision by using the Azure CLI. For more information, see the Examine configuration file with Azure CLI section.

Troubleshoot known issues

If the latest changes aren't reflected in the applications, check the following items based on the Refresh strategies section:

• Confirm that the Git repo is updated correctly by checking the following items:
  • Confirm that the branch of the desired config file changes is updated.
  • Confirm that the pattern configured in the Application Configuration Service matches the updated config files.
  • Confirm that the application is bound to the Application Configuration Service.
• Confirm that the Application Configuration Service is using the correct Git revisions as described in the Examine Git revisions of the configuration files section.
• Confirm that the ConfigMap containing the configuration file for the Pattern used by the application is updated, as described in the Examine configuration file in ConfigMap section of this article. If it isn't updated, raise a ticket.
• Confirm that the ConfigMap is mounted to the application as a file, as described in the Examine configuration file in the app section of this article. If the file isn't updated, wait for the Kubernetes refresh interval (1 minute), or force a refresh by restarting the application.

After checking these items, the applications should be able to read the updated configurations. If the applications still aren't updated, raise a ticket.

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