Inter-App Communication Callback Reference¶

validate_configuration_change¶

This callback is a synchronous callback.

This callback is called as part of ALTER APPLICATION SET CONFIGURATION VALUE command. This callback lets the app perform additional custom validation on the value provided by the server app. If the callback fails, such as with a syntax error, or if the callback returns and error, the set command fails and the new value is not set.

validate_configuration_change(configuration_name, configuration_value)

{
  "type": "SUCCESS | ERROR",
  "payload":{
      "error_message": "Error message indicating the validation failure"
  }
}

before_configuration_change¶

This callback is a synchronous callback. This callback is called as part of ALTER APPLICATION SET CONFIGURATION VALUE and ALTER APPLICATION UNSET CONFIGURATION commands. This callback lets the app perform further operations based on the configuration value set. The value passed into the callback is null for the ALTER APPLICATION UNSET CONFIGURATION command.

before_configuration_change(configuration_name, configuration_value)

after_configuration_change¶

This callback is an asynchronous callback. This callback is called after the ALTER APPLICATION SET CONFIGURATION VALUE and ALTER APPLICATION UNSET CONFIGURATION commands complete. This callback lets the client app be notified when a value is provided by the server app.

after_configuration_change(configuration_name)

session.sql(f"""
  SHOW CONFIGURATIONS ->>
      SELECT "status", "value"
      FROM $1
      WHERE "name" = '{configuration_name}';
  """);

after_server_connection_change¶

This callback is an asynchronous callback. This callback is called after the ALTER APPLICATION APPROVE SPECIFICATION or ALTER APPLICATION DECLINE SPECIFICATION command completes. This callback lets the client app be notified when the connection to a server app has been changed, such as when a new connection is established, or the connection to the server is broken.

after_server_connection_change(server_name)

session.sql(f"""
  SHOW SPECIFICATIONS ->>
  SELECT "status"
  FROM $1
  WHERE PARSE_JSON("definition"):"SERVER_APPLICATION"::STRING = '{server_name}';
  """);

after_client_connection_change¶

This callback is an asynchronous callback. This callback is called after the ALTER APPLICATION APPROVE SPECIFICATION or ALTER APPLICATION DECLINE SPECIFICATION command completes. This callback lets the server app be notified when one of its clients has changed, such as when a new connection is established, or the client drops the connection.

after_client_connection_change(client_name)

session.sql(f"""
  SHOW GRANTS TO APPLICATION {client_name} ->>
  SELECT "name"
  FROM $1
  WHERE "granted_on" = 'APPLICATION_ROLE'
      AND STARTSWITH("name", CURRENT_DATABASE())
  """);

after_server_version_change¶

This callback is an asynchronous callback. This callback is called after the server app’s version or patch number changes. This lets the client app react to the upgrade or downgrade.

after_server_version_change(server_name)

session.sql(f"""
  SHOW APPLICATIONS ->>
  SELECT "version", "patch"
  FROM $1
  WHERE "name" = {server_name}
  """);

after_specification_change¶

This callback is an asynchronous callback. This callback is called after the ALTER APPLICATION APPROVE SPECIFICATION or ALTER APPLICATION DECLINE SPECIFICATION commands complete. This callback lets the server app be notified when a new specification has been created or updated.

For inter-app communication, this callback replaces the functionality of the specification_action callback. You can only specify one of after_specification_change or specification_action in the manifest file. For information about the specification_action callback, see Using callback functions with app specifications.

after_specification_change(spec_name)

session.sql(f"""
  SHOW SPECIFICATIONS ->>
      SELECT "status"
      FROM $1
      WHERE "name" = '{spec_name}';
  """);