11.4.2. Configuring score calculation using Drools

Procedure

1. Add a scoreDrl resource in the classpath to use the decision engine as a score function. In the cloudBalancingSolverConfig.xml file, add or uncomment the setting:

     <scoreDirectorFactory>
       <scoreDrl>org/optaplanner/examples/cloudbalancing/solver/cloudBalancingScoreRules.drl</scoreDrl>
     </scoreDirectorFactory>

2. Create the hard constraints. These constraints ensure that all computers have enough CPU, RAM and network bandwidth to support all their processes:

   例11.7 cloudBalancingScoreRules.drl - Hard Constraints

   ...
   
   import org.optaplanner.examples.cloudbalancing.domain.CloudBalance;
   import org.optaplanner.examples.cloudbalancing.domain.CloudComputer;
   import org.optaplanner.examples.cloudbalancing.domain.CloudProcess;
   
   global HardSoftScoreHolder scoreHolder;
   
   // ############################################################################
   // Hard constraints
   // ############################################################################
   
   rule "requiredCpuPowerTotal"
       when
           $computer : CloudComputer($cpuPower : cpuPower)
           accumulate(
               CloudProcess(
                   computer == $computer,
                   $requiredCpuPower : requiredCpuPower);
               $requiredCpuPowerTotal : sum($requiredCpuPower);
               $requiredCpuPowerTotal > $cpuPower
           )
       then
           scoreHolder.addHardConstraintMatch(kcontext, $cpuPower - $requiredCpuPowerTotal);
   end
   
   rule "requiredMemoryTotal"
       ...
   end
   
   rule "requiredNetworkBandwidthTotal"
       ...
   end

3. Create a soft constraint. This constraint minimizes the maintenance cost. It is applied only if hard constraints are met:

   例11.8 cloudBalancingScoreRules.drl - Soft Constraints

   // ############################################################################
   // Soft constraints
   // ############################################################################
   
   rule "computerCost"
       when
           $computer : CloudComputer($cost : cost)
           exists CloudProcess(computer == $computer)
       then
           scoreHolder.addSoftConstraintMatch(kcontext, - $cost);
   end