Retrieving configuration data without Amazon AppConfig Agent - Amazon AppConfig
Retrieving configurations by directly calling APIs
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Retrieving configuration data without Amazon AppConfig Agent

On Nov 18, 2021, Amazon AppConfig released a new data plane service. This service replaces the previous process of retrieving configuration data by using the GetConfiguration API action. The data plane service uses two new API actions, StartConfigurationSession and GetLatestConfiguration. The data plane service also uses new endpoints.

If you started using Amazon AppConfig before January 28, 2022, the service might be calling the GetConfiguration API action directly or it might be using a client provided by Amazon, such as the Amazon AppConfig Agent Lambda extension, to call this API action. If you call the GetConfiguration API action directly, take steps to use the StartConfigurationSession and GetLatestConfiguration API actions. If you are using the Amazon AppConfig Agent Lambda extension, see the section titled How this change impacts the Amazon AppConfig Agent Lambda extension later in this topic.

The new data plane API actions offer the following benefits over the GetConfiguration API action, which is now deprecated.

  1. You don't need to manage a ClientID parameter. With the data plane service, ClientID is managed internally by the session token created by StartConfigurationSession.

  2. You no longer need to include ClientConfigurationVersion to indicate the cached version of your configuration data. With the data plane service, ClientConfigurationVersion is managed internally by the session token created by StartConfigurationSession.

  3. The new dedicated endpoint for data plane API calls improves code structure by separating control plane and data plane calls.

  4. The new data plane service improves future extensibility for data plane operations. By utilizing a configuration session that manages configuration data retrieval, the Amazon AppConfig team can create more powerful enhancements in the future.

Migrating from GetConfiguration to GetLatestConfiguration

To start using the new data plane service, you need to update your code that calls the GetConfiguration API action. Start a configuration session by using the StartConfigurationSession API action, and then call the GetLatestConfiguration API action to retrieve configuration data. To improve performance, we recommend you cache your configuration data locally. For more information, see Retrieving configurations by directly calling APIs.

How this change impacts the Amazon AppConfig Agent Lambda extension

This change has no direct impact on how the Amazon AppConfig Agent Lambda extension works. Older versions of the Amazon AppConfig Agent Lambda extension called the GetConfiguration API action on your behalf. Newer versions call the data plane API actions. If you are using the Amazon AppConfig Lambda extension, we recommend you update your extension to the most recent Amazon Resource Name (ARN) and update permissions for the new API calls. For more information, see Using Amazon AppConfig Agent with Amazon Lambda.

Retrieving configurations by directly calling APIs

Your application retrieves configuration data by first establishing a configuration session using the StartConfigurationSession API operation. Your session's client then makes periodic calls to GetLatestConfiguration to check for and retrieve the latest data available.

When calling StartConfigurationSession, your code sends the following information:

  • Identifiers (ID or name) of an Amazon AppConfig application, environment, and configuration profile that the session tracks.

  • (Optional) The minimum amount of time the session's client must wait between calls to GetLatestConfiguration.

In response, Amazon AppConfig provides an InitialConfigurationToken to be given to the session's client and used the first time it calls GetLatestConfiguration for that session.

Important

This token should only be used once in your first call to GetLatestConfiguration. You must use the new token in the GetLatestConfiguration response (NextPollConfigurationToken) in each subsequent call to GetLatestConfiguration. To support long poll use cases, the tokens are valid for up to 24 hours. If a GetLatestConfiguration call uses an expired token, the system returns BadRequestException.

When calling GetLatestConfiguration, your client code sends the most recent ConfigurationToken value it has and receives in response:

  • NextPollConfigurationToken: the ConfigurationToken value to use on the next call to GetLatestConfiguration.

  • NextPollIntervalInSeconds: the duration the client should wait before making its next call to GetLatestConfiguration.

  • The configuration: the latest data intended for the session. This may be empty if the client already has the latest version of the configuration.

Important

Note the following important information.

  • The StartConfigurationSession API should only be called once per application, environment, configuration profile, and client to establish a session with the service. This is typically done in the startup of your application or immediately prior to the first retrieval of a configuration.

  • If your configuration is deployed using a KmsKeyIdentifier, your request to receive the configuration must include permission to call kms:Decrypt. For more information, see Decrypt in the Amazon Key Management Service API Reference.

  • The API operation previously used to retrieve configuration data, GetConfiguration, is deprecated. The GetConfiguration API operation does not support encrypted configurations.

Retrieving a configuration example

The following Amazon CLI example demonstrates how to retrieve configuration data by using the Amazon AppConfig Data StartConfigurationSession and GetLatestConfiguration API operations. The first command starts a configuration session. This call includes the IDs (or names) of the Amazon AppConfig application, the environment, and the configuration profile. The API returns an InitialConfigurationToken used to fetch your configuration data.

aws appconfigdata start-configuration-session \
    --application-identifier application_name_or_ID \
    --environment-identifier environment_name_or_ID \
    --configuration-profile-identifier configuration_profile_name_or_ID

The system responds with information in the following format.

{
   "InitialConfigurationToken": initial configuration token
}

After starting a session, use InitialConfigurationToken to call GetLatestConfiguration to fetch your configuration data. The configuration data is saved to the mydata.json file.

aws appconfigdata get-latest-configuration \
    --configuration-token initial configuration token mydata.json

The first call to GetLatestConfiguration uses the ConfigurationToken obtained from StartConfigurationSession. The following information is returned.

{
    "NextPollConfigurationToken" : next configuration token,
    "ContentType" : content type of configuration,
    "NextPollIntervalInSeconds" : 60
}

Subsequent calls to GetLatestConfiguration must provide NextPollConfigurationToken from the previous response.

aws appconfigdata get-latest-configuration \
    --configuration-token next configuration token mydata.json
Important

Note the following important details about the GetLatestConfiguration API operation:

  • The GetLatestConfiguration response includes a Configuration section that shows the configuration data. The Configuration section only appears if the system finds new or updated configuration data. If the system doesn't find new or updated configuration data, then the Configuration data is empty.

  • You receive a new ConfigurationToken in every response from GetLatestConfiguration.

  • We recommend tuning the polling frequency of your GetLatestConfiguration API calls based on your budget, the expected frequency of your configuration deployments, and the number of targets for a configuration.