rerun/src/main/java/org/apache/falcon/rerun/policy/ExpBackoffPolicy.java

/**
 * 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.falcon.rerun.policy;

import org.apache.falcon.FalconException;
import org.apache.falcon.entity.v0.Frequency;
import org.apache.falcon.expression.ExpressionHelper;

import java.util.Date;

/**
 * An implementation of the Rerun policy that backs off exponentially.
 */
public class ExpBackoffPolicy extends AbstractRerunPolicy {

    @Override
    public long getDelay(Frequency delay, int eventNumber) throws FalconException {
        return (long) (getDurationInMilliSec(delay) * Math.pow(getPower(), eventNumber));
    }

    @Override
    public long getDelay(Frequency delay, Date nominalTime, Date cutOffTime) throws FalconException {
        ExpressionHelper evaluator = ExpressionHelper.get();
        Date now = new Date();
        Date lateTime = nominalTime;
        long delayMilliSeconds = evaluator.evaluate(delay.toString(), Long.class);
        int factor = 1;
        // TODO we can get rid of this using formula
        while (lateTime.compareTo(now) <= 0) {
            lateTime = addTime(lateTime, (int) (factor * delayMilliSeconds));
            factor *= getPower();
        }
        if (lateTime.after(cutOffTime)) {
            lateTime = cutOffTime;
        }

        return (lateTime.getTime() - nominalTime.getTime());
    }

    protected int getPower() {
        return 2;
    }
}