org.apache.nifi.processor.SchedulingContext Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.nifi.processor;
import org.apache.nifi.components.PropertyDescriptor;
import org.apache.nifi.components.PropertyValue;
import org.apache.nifi.controller.ControllerServiceLookup;
public interface SchedulingContext extends ProcessContext {
/**
*
* Indicates to the framework that the Controller Service with the given
* identifier will be used by this Processor. This will prevent any Data
* Flow Manager from disabling the Controller Service while this Processor
* is still running.
*
*
*
* Generally, a Controller Service is accessed by indicating in a
* {@link PropertyDescriptor} that the PropertyDescriptor identifies a
* Controller Service via the
* {@link PropertyDescriptor.Builder#identifiesControllerService(Class) identifiesControllerService(Class)}
* method and then calling
* {@link ProcessContext#getProperty(PropertyDescriptor)}.{@link PropertyValue#asControllerService(Class) asControllerService(Class)}.
* In this case, it is not necessary to lease the Controller Service, as the
* Framework will handle this.
*
*
*
* There are, however, cases in which a Controller Service must be accessed
* in a different way, via the {@link ControllerServiceLookup} (accessed via
* {@link ProcessContext#getControllerServiceLookup()}). In this case, the
* Controller Service that is obtained from the ControllerServiceLookup can
* be disabled by a Data Flow Manager while it is still in use by a
* Processor, causing IllegalStateException to be thrown whenever the
* Processor attempts to interact with the service. This method provides a
* mechanism by which a Processor is able to indicate that the Controller
* Service with the given identifier should not be disabled while this
* Processor is running.
*
*
*
* For any Controller Service that is leased by calling this method, the
* lease will automatically be terminated, allowing the Controller Service
* to be disabled, whenever the Processor is stopped.
*
*
* @param identifier
*
* @throws IllegalArgumentException if no Controller Service exists with the
* given identifier
*/
void leaseControllerService(String identifier);
}