Resource optimization: Quick start with Drools Planner

CloudComputer.java

public class CloudComputer ... {

    private int cpuPower;
    private int memory;
    private int networkBandwidth;
    private int cost;

    ... // getters

}

CloudProcess.java

@PlanningEntity(...)
public class CloudProcess ... {

    private int requiredCpuPower;
    private int requiredMemory;
    private int requiredNetworkBandwidth;

    private CloudComputer computer;

    ... // getters

    @PlanningVariable(...)
    @ValueRange(type = ValueRangeType.FROM_SOLUTION_PROPERTY, solutionProperty = "computerList")
    public CloudComputer getComputer() {
        return computer;
    }

    public void setComputer(CloudComputer computer) {
        computer = computer;
    }

    public CloudProcess clone() {
        CloudProcess clone = new CloudProcess();
        clone.id = id;
        clone.requiredCpuPower = requiredCpuPower;
        clone.requiredMemory = requiredMemory;
        clone.requiredNetworkBandwidth = requiredNetworkBandwidth;
        clone.computer = computer;
        return clone;
    }

    ...

}

CloudBalance.java

public class CloudBalance ... implements Solution<HardAndSoftScore> {

    private List<CloudComputer> computerList;

    private List<CloudProcess> processList;

    private HardAndSoftScore score;

    public List<CloudComputer> getComputerList() {
        return computerList;
    }

    @PlanningEntityCollectionProperty
    public List<CloudProcess> getProcessList() {
        return processList;
    }

    ...

    public HardAndSoftScore getScore() {
        return score;
    }

    public void setScore(HardAndSoftScore score) {
        this.score = score;
    }

    // ************************************************************************
    // Complex methods
    // ************************************************************************

    public Collection<? extends Object> getProblemFacts() {
        List<Object> facts = new ArrayList<Object>();
        facts.addAll(computerList);
        // Do not add the planning entity's (processList) because that will be done automatically
        return facts;
    }

    /**
     * Clone will only deep copy the {@link #processList}.
     */
    public CloudBalance cloneSolution() {
        CloudBalance clone = new CloudBalance();
        clone.id = id;
        clone.computerList = computerList;
        List<CloudProcess> clonedProcessList = new ArrayList<CloudProcess>(
                processList.size());
        for (CloudProcess process : processList) {
            CloudProcess clonedProcess = process.clone();
            clonedProcessList.add(clonedProcess);
        }
        clone.processList = clonedProcessList;
        clone.score = score;
        return clone;
    }

    ...

}

CloudBalancingSimpleScoreCalculator.java

public class CloudBalancingSimpleScoreCalculator implements SimpleScoreCalculator<CloudBalance> {

    /**
     * A very simple implementation. The double loop can easily be removed by using Maps as shown in
     * {@link CloudBalancingMapBasedSimpleScoreCalculator#calculateScore(CloudBalance)}.
     */
    public HardAndSoftScore calculateScore(CloudBalance cloudBalance) {
        int hardScore = 0;
        int softScore = 0;
        for (CloudComputer computer : cloudBalance.getComputerList()) {
            int cpuPowerUsage = 0;
            int memoryUsage = 0;
            int networkBandwidthUsage = 0;
            boolean used = false;

            // Calculate usage
            for (CloudProcess process : cloudBalance.getProcessList()) {
                if (computer.equals(process.getComputer())) {
                    cpuPowerUsage += process.getRequiredCpuPower();
                    memoryUsage += process.getRequiredMemory();
                    networkBandwidthUsage += process.getRequiredNetworkBandwidth();
                    used = true;
                }
            }
            
            // Hard constraints
            int cpuPowerAvailable = computer.getCpuPower() - cpuPowerUsage;
            if (cpuPowerAvailable < 0) {
                hardScore += cpuPowerAvailable;
            }
            int memoryAvailable = computer.getMemory() - memoryUsage;
            if (memoryAvailable < 0) {
                hardScore += memoryAvailable;
            }
            int networkBandwidthAvailable = computer.getNetworkBandwidth() - networkBandwidthUsage;
            if (networkBandwidthAvailable < 0) {
                hardScore += networkBandwidthAvailable;
            }
            
            // Soft constraints
            if (used) {
                softScore -= computer.getCost();
            }
        }
        return DefaultHardAndSoftScore.valueOf(hardScore, softScore);
    }

}

cloudBalancingScoreRules.drl - hard constraints

...

import org.drools.planner.examples.cloudbalancing.domain.CloudBalance;
import org.drools.planner.examples.cloudbalancing.domain.CloudComputer;
import org.drools.planner.examples.cloudbalancing.domain.CloudProcess;

global HardAndSoftScoreHolder scoreHolder;

// ############################################################################
// Hard constraints
// ############################################################################

rule "requiredCpuPowerTotal"
    when
        $computer : CloudComputer($cpuPower : cpuPower)
        $requiredCpuPowerTotal : Number(intValue > $cpuPower) from accumulate(
            CloudProcess(
                computer == $computer,
                $requiredCpuPower : requiredCpuPower),
            sum($requiredCpuPower)
        )
    then
        insertLogical(new IntConstraintOccurrence("requiredCpuPowerTotal", ConstraintType.NEGATIVE_HARD,
                $requiredCpuPowerTotal.intValue() - $cpuPower,
                $computer));
end

rule "requiredMemoryTotal"
    ...
end

rule "requiredNetworkBandwidthTotal"
    ...
end

// ############################################################################
// Calculate hard score
// ############################################################################

// Accumulate hard constraints
rule "hardConstraintsBroken"
        salience -1 // Do the other rules first (optional, for performance)
    when
        $hardTotal : Number() from accumulate(
            IntConstraintOccurrence(constraintType == ConstraintType.NEGATIVE_HARD, $weight : weight),
            sum($weight)
        )
    then
        scoreHolder.setHardConstraintsBroken($hardTotal.intValue());
end

cloudBalancingScoreRules.drl - soft constraints

// ############################################################################
// Soft constraints
// ############################################################################

rule "computerCost"
    when
        $computer : CloudComputer($cost : cost)
        exists CloudProcess(computer == $computer)
    then
        insertLogical(new IntConstraintOccurrence("computerCost", ConstraintType.NEGATIVE_SOFT,
                $cost,
                $computer));
end

// ############################################################################
// Calculate soft score
// ############################################################################

// Accumulate soft constraints
rule "softConstraintsBroken"
        salience -1 // Do the other rules first (optional, for performance)
    when
        $softTotal : Number() from accumulate(
            IntConstraintOccurrence(constraintType == ConstraintType.NEGATIVE_SOFT, $weight : weight),
            sum($weight)
        )
    then
        scoreHolder.setSoftConstraintsBroken($softTotal.intValue());
end