il.ac.technion.datacenter.sla.SLA.java Source code

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Here is the source code for il.ac.technion.datacenter.sla.SLA.java

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/**
 * Greedy_Recovery - Technion, Israel Institute of Technology
 * 
 * Author: Assaf Israel, 2012
 * Created: 12/03/2012
 */
package il.ac.technion.datacenter.sla;

import il.ac.technion.misc.PeriodConverter;

import org.joda.time.Period;

import com.google.java.contract.Ensures;

/**
 *   Service License Agreement of Cloud Providers.
 *  Exposes the CP Availability commitments, and the 
 *  compensation scale.  
 */
public abstract class SLA {

    final public Period billingPeriod;

    private Period totalDownTime;

    /**
     * @param billingPeriod E.g: <code>new Period().withYears(1);</code>
     */
    public SLA(Period billingPeriod) {
        this.billingPeriod = billingPeriod;
        this.totalDownTime = new Period();
    }

    /**
     * @return the current period of unavailability. 
     */
    public Period getDownTime() {
        return totalDownTime;
    }

    /**
     * Reports a period of unavailability. All reported
     * periods are accumulated, thus a compensation to the client
     * may be needed.
     */
    public void reportDownTime(Period downTime) {
        totalDownTime = totalDownTime.plus(downTime);
    }

    /**
     * @return A percentage of yearly recorded availability.
     * e.g. 99.95, 99.99, 99.999 
     */
    @Ensures({ "result <= 100.0", "result >= 0.0" })
    public double availability() {
        return availability(Period.ZERO);
    }

    public double availability(Period downTime) {
        return ((double) PeriodConverter.toSeconds(billingPeriod.minus(totalDownTime.plus(downTime)))
                / PeriodConverter.toSeconds(billingPeriod)) * 100.0;
    }

    /**
     * @return A percentage of yearly availability the CP commits upon.
     * e.g. 99.95, 99.99, 99.999 
     */
    @Ensures({ "result <= 100.0", "result > 0.0" })
    public abstract double availabilityContract();

    /**
     * Returns the amount of compensation the client will be entitled
     * to, in case the total down-time is increased by the <code>estimatedDownTime</code>.  
     * @return If <code>estimatedDownTime</code> is a 0-length period will return 
     * the compensation entitled to the client due to <code>getDownTime() + estimatedDownTime</code>
     * period exceeding (or not) the allowed availability in the SLA. 
     * In case the time period does not exceed the allowed down time period, the returned
     * compensation is 0.   
     */
    @Ensures({ "estimatedDownTime != null", "zeroCostCheck(old(estimatedDownTime),result)", "result >= 0.0" })
    public abstract double compensation(Period estimatedDownTime);

    /**
     * Returns the amount of compensation the client will be entitled
     * to.  
     * @return The compensation entitled to the client due to <code>getDownTime()</code>
     * period exceeding (or not) the allowed availability in the SLA. 
     * In case the time period does not exceed the allowed down time period, the returned
     * compensation is 0.
     */
    @Ensures("result >= 0.0")
    public abstract double compensation();

    @SuppressWarnings("unused")
    private boolean zeroCostCheck(Period estimatedDownTime, double result) {
        if (PeriodConverter.toMillis(totalDownTime.plus(estimatedDownTime)) < (100.0 - availabilityContract())
                * PeriodConverter.toMillis(billingPeriod))
            return result == 0.0;
        return true;
    }

    /**
     * Adds a random generated downtime period, based on the <code>noise</code> parameter.
     * The implementation of the random period generation is SLA-Implementation dependent. 
     * @param noise A general parameter used by the implementations to influence on the 
     * randomnece of the downtime period. 
     * @return The downtime period added to the SLA.
     */
    public abstract Period addRandomDowntime(double noise);
}