library/src/main/java/com/datatorrent/lib/math/ChangeAlert.java

/*
 * Copyright (c) 2013 DataTorrent, Inc. ALL Rights Reserved.
 *
 * Licensed 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 com.datatorrent.lib.math;

import javax.validation.constraints.Min;

import com.datatorrent.api.DefaultInputPort;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.api.annotation.InputPortFieldAnnotation;
import com.datatorrent.api.annotation.OutputPortFieldAnnotation;
import com.datatorrent.lib.util.BaseNumberValueOperator;
import com.datatorrent.lib.util.KeyValPair;

/**
 * Compares consecutive input data values, emits <value,percent change value> pair on alert output port, if percent change exceeds certain thresh hold value.
 * <p>
 * Operator is StateFull since current value is stored for comparison in next window. <br>
 * This operator can not be partitioned, partitioning will result in inconsistent base value
 * across replicated copies.
 * <br>
 *
 * <b>Ports</b>:<br>
 * <b>data</b>: expects KeyValPair&lt;K,V extends Number&gt;<br>
 * <b>alert</b>: emits KeyValPair&lt;K,KeyValPair&lt;V,Double&gt;&gt;(1)<br>
 * <br>
 * <b>Properties</b>:<br>
 * <b>threshold</b>: The threshold of change between consecutive tuples of the
 * same key that triggers an alert tuple<br>
 * <b>inverse</b>: if set to true the key in the filter will block tuple<br>
 * <b>filterBy</b>: List of keys to filter on<br>
 * <br>
 * <b>Specific compile time checks</b>: None<br>
 * <b>Specific run time checks</b>: None<br>
 * <br>
 * @displayname: Change Alert
 * @category: math
 * @tags: change, key value, numeric, percentage
 * @since 0.3.3
 */
public class ChangeAlert<V extends Number> extends BaseNumberValueOperator<V>
{
	/**
	 * Input port that takes in a number.
	 */
	@InputPortFieldAnnotation(name = "data")
	public final transient DefaultInputPort<V> data = new DefaultInputPort<V>()
	{
		/**
		 * Process each key, compute change or percent, and emit it. If we get 0 as
		 * tuple next will be skipped.
		 */
		@Override
		public void process(V tuple)
		{
			double tval = tuple.doubleValue();
			if (baseValue == 0) { // Avoid divide by zero, Emit an error tuple?
				baseValue = tval;
				return;
			}
			double change = tval - baseValue;
			double percent = (change / baseValue) * 100;
			if (percent < 0.0) {
				percent = 0.0 - percent;
			}
			if (percent > percentThreshold) {
				KeyValPair<V, Double> kv = new KeyValPair<V, Double>(cloneKey(tuple),
						percent);
				alert.emit(kv);
			}
			baseValue = tval;
		}
	};
	
	
	/**
	 * Output port which emits a key value pair.
	 */
	@OutputPortFieldAnnotation(name = "alert")
	public final transient DefaultOutputPort<KeyValPair<V, Double>> alert = new DefaultOutputPort<KeyValPair<V, Double>>();
	
	/**
	 * baseValue is a state full field. It is retained across windows
	 */
	private double baseValue = 0;
	@Min(1)
	private double percentThreshold = 0.0;

	/**
	 * getter function for threshold value
	 * 
	 * @return threshold value
	 */
	@Min(1)
	public double getPercentThreshold()
	{
		return percentThreshold;
	}

	/**
	 * setter function for threshold value
	 */
	public void setPercentThreshold(double d)
	{
		percentThreshold = d;
	}
}