Code for round robin partition technique

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package org.apache.stratos.autoscaler.algorithms.partition;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.stratos.autoscaler.algorithms.PartitionAlgorithm;
import org.apache.stratos.autoscaler.context.partition.PartitionContext;

/**
* This class is used for selecting a {@link PartitionContext} in round robin manner and checking availability of
* {@link PartitionContext}s according to the partitions defined
* in {@link org.apache.stratos.autoscaler.pojo.policy.deployment.DeploymentPolicy}
*/
public class RoundRobin implements PartitionAlgorithm {

private static final Log log = LogFactory.getLog(RoundRobin.class);

@Override
public PartitionContext getNextScaleUpPartitionContext(PartitionContext[] partitionContexts) {

if (partitionContexts == null) {
return null;
}

int selectedIndex = 0;
int lowestInstanceCount = partitionContexts[0].getNonTerminatedMemberCount();

for (int partitionIndex = 0; partitionIndex < partitionContexts.length; partitionIndex++) {

// it means we have to choose the current partitionIndex, no need to continue the loop
if (lowestInstanceCount == 0) {
break;
}

if (partitionContexts[partitionIndex].getNonTerminatedMemberCount() < lowestInstanceCount
&& !partitionContexts[partitionIndex].isObsoletePartition()) {
lowestInstanceCount = partitionContexts[partitionIndex].getNonTerminatedMemberCount();
selectedIndex = partitionIndex;
}
}

if (partitionContexts[selectedIndex].getNonTerminatedMemberCount() < partitionContexts[selectedIndex].getMax()) {

if (log.isDebugEnabled()) {
log.debug(String.format("[round-robin algorithm] [scale-up] [partition] %s has space to create members. " +
"[non terminated count] %s [max] %s"
, partitionContexts[selectedIndex].getPartitionId(),
partitionContexts[selectedIndex].getNonTerminatedMemberCount(),
partitionContexts[selectedIndex].getMax()));
}
return partitionContexts[selectedIndex];
} else {

return null;
}
}

@Override
public PartitionContext getNextScaleDownPartitionContext(PartitionContext[] partitionContexts) {

if (partitionContexts == null) {
return null;
}

int selectedIndex = 0;
int highestInstanceCount = partitionContexts[0].getNonTerminatedMemberCount();

for (int partitionIndex = partitionContexts.length - 1; partitionIndex >= 0; partitionIndex--) {

if (partitionContexts[partitionIndex].getNonTerminatedMemberCount() > highestInstanceCount
&& !partitionContexts[partitionIndex].isObsoletePartition()) {

highestInstanceCount = partitionContexts[partitionIndex].getNonTerminatedMemberCount();
selectedIndex = partitionIndex;
}
}

if (partitionContexts[selectedIndex].getNonTerminatedMemberCount() <= partitionContexts[selectedIndex].getMax()) {

if (log.isDebugEnabled()) {
log.debug(String.format("[round-robin algorithm] [scale-down] [partition] %s has has members that" +
" can be removed.[non terminated count] %s ", partitionContexts[selectedIndex].getPartitionId(),
partitionContexts[selectedIndex].getNonTerminatedMemberCount()));
}
return partitionContexts[selectedIndex];
} else {

return null;
}
}


}