Package org.apache.nifi.controller

Interface VerifiableControllerService

public interface VerifiableControllerService

Any Controller Service that implements this interface will be provided the opportunity to verify a given configuration of the Controller Service. This allows the Controller Service to provide meaningful feedback to users when configuring the dataflow.

Generally speaking, verification differs from validation in that validation is expected to be very quick and run often. If a Controller Service is not valid, it cannot be started. However, verification may be more expensive or time-consuming to complete. For example, validation may ensure that a username is provided for connecting to an external service but should not perform any sort of network connection in order to verify that the username is accurate. Verification, on the other hand, may create resources such as network connections, may be more expensive to complete, and may be run only when a user invokes the action (though verification may later occur at other stages, such as when starting a component).

Verification is allowed to be run only when a Controller Service is fully disabled. Therefore, any initialization logic that may need to be performed before the Controller Service is triggered may also be required for verification. However, the framework is not responsible for triggering the Lifecycle management stages, such as @OnScheduled before triggering the verification. Such methods should be handled by the verify(ConfigurationContext, ComponentLog, Map) itself. The verify(ConfigurationContext, ComponentLog, Map) method will only be called if the configuration is valid according to the validation rules (i.e., all Property Descriptors' validators and customValidate methods have indicated that the configuration is valid).

  • Method Details

    • verify

      List<ConfigVerificationResult> verify(ConfigurationContext context, ComponentLog verificationLogger, Map<String,String> variables)
      Verifies that the configuration defined by the given ConfigurationContext is valid.
      Parameters:
      context - the ProcessContext that contains the necessary configuration
      verificationLogger - a logger that can be used during verification. While the typical logger can be used, doing so may result in producing bulletins, which can be confusing.
      variables - a Map of key/value pairs that can be used to resolve variables referenced in property values via Expression Language
      Returns:
      a List of ConfigVerificationResults, each illustrating one step of the verification process that was completed