org.apache.nifi.annotation.behavior.TriggerWhenEmpty 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.annotation.behavior;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
*
* Marker annotation a {@link org.apache.nifi.processor.Processor Processor}
* implementation can use to indicate that the Processor should still be
* triggered even when it has no data in its work queue.
*
*
*
* A Processor is scheduled to be triggered based on its configured Scheduling Period
* and Scheduling Strategy. However, when the scheduling period elapses, the Processor
* will not be scheduled if it has no work to do. Normally, a Processor is said to have
* work to do if one of the following circumstances is true:
*
*
*
* - An incoming Connection has data in its queue
* - The Processor has no incoming Connections.
* - All incoming Connections are self-loops (both the source and destination of the Connection are the same Processor).
*
*
*
* If the Processor needs to be triggered to run even when the above conditions are all
* false, the Processor's class can be annotated with this annotation, which
* will cause the Processor to be triggered, even if its incoming queues are empty.
*
*/
@Documented
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
public @interface TriggerWhenEmpty {
}