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brooklyn.policy.loadbalancing.BalancingStrategy Maven / Gradle / Ivy
package brooklyn.policy.loadbalancing;
import java.text.MessageFormat;
import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import brooklyn.entity.Entity;
import brooklyn.location.Location;
/**
* Represents an abstract algorithm for optimally balancing worker "items" among several "containers" based on the workloads
* of the items, and corresponding high- and low-thresholds on the containers.
*
* TODO: extract interface, provide default implementation
* TODO: remove legacy code comments
*/
public class BalancingStrategy {
// FIXME Bad idea to use MessageFormat.format in this way; if toString of entity contains
// special characters interpreted by MessageFormat, then it will all break!
// This is a modified version of the watermark elasticity policy from Monterey v3.
private static final Logger LOG = LoggerFactory.getLogger(BalancingStrategy.class);
private static final int MAX_MIGRATIONS_PER_BALANCING_NODE = 20; // arbitrary (Splodge)
private static final boolean BALANCE_COLD_PULLS_IN_SAME_RUN_AS_HOT_PUSHES = false;
private final String name;
private final BalanceablePoolModel model;
private final PolicyUtilForPool helper;
// private boolean loggedColdestTooHigh = false;
// private boolean loggedHottestTooLow = false;
public BalancingStrategy(String name, BalanceablePoolModel model) {
this.name = name;
this.model = model;
this.helper = new PolicyUtilForPool(model);
}
public String getName() {
return name;
}
public void rebalance() {
checkAndApplyOn(model.getPoolContents());
}
public int getMaxMigrationsPerBalancingNode() {
return MAX_MIGRATIONS_PER_BALANCING_NODE;
}
public BalanceablePoolModel getDataProvider() {
return model;
}
// This was the entry point for the legacy policy.
private void checkAndApplyOn(final Collection dirtyNodesSupplied) {
Collection dirtyNodes = dirtyNodesSupplied;
// if (startTime + FORCE_ALL_NODES_IF_DELAYED_FOR_MILLIS < System.currentTimeMillis()) {
// Set allNodes = new LinkedHashSet();
// allNodes.addAll(dirtyNodes);
// dirtyNodes = allNodes;
// allNodes.addAll(getDataProvider().getPoolContents());
// if (LOG.isDebugEnabled())
// LOG.debug("policy "+getDataProvider().getAbbr()+" running after delay ("+
// TimeUtils.makeTimeString(System.currentTimeMillis() - startTime)+", analysing all nodes: "+
// dirtyNodes);
// }
// nodeFinder.optionalCachedNodesWithBacklogDetected.clear();
// boolean gonnaGrow = growPool(dirtyNodes);
// getDataProvider().waitForAllTransitionsComplete();
boolean gonnaGrow = false;
Set nonFrozenDirtyNodes = new LinkedHashSet(dirtyNodes);
// boolean gonnaShrink = false;
// if (!gonnaGrow && !DONT_SHRINK_UNLESS_BALANCED) {
// gonnaShrink = shrinkPool(nonFrozenDirtyNodes);
// getDataProvider().waitForAllTransitionsComplete();
// }
if (getDataProvider().getPoolSize() >= 2) {
boolean didBalancing = false;
for (NodeType a : nonFrozenDirtyNodes) {
didBalancing |= balanceItemsOnNodesInQuestion(a, gonnaGrow);
// getMutator().waitForAllTransitionsComplete();
}
if (didBalancing) {
return;
}
}
// if (!gonnaGrow && DONT_SHRINK_UNLESS_BALANCED) {
// gonnaShrink = shrinkPool(nonFrozenDirtyNodes);
// getDataProvider().waitForAllTransitionsComplete();
// }
// if (gonnaGrow || gonnaShrink)
// //don't log 'doing nothing' message
// return;
// if (LOG.isDebugEnabled()) {
// double poolTotal = getDataProvider().getPoolPredictedWorkrateTotal();
// int poolSize = getDataProvider().getPoolPredictedSize();
// LOG.debug(MessageFormat.format("policy "+getDataProvider().getAbbr()+" did nothing; pool workrate is {0,number,#.##} x {1} nodes",
// 1.0*poolTotal/poolSize, poolSize));
// }
}
protected boolean balanceItemsOnNodesInQuestion(NodeType questionedNode, boolean gonnaGrow) {
double questionedNodeTotalWorkrate = getDataProvider().getTotalWorkrate(questionedNode);
boolean balanced = balanceItemsOnHotNode(questionedNode, questionedNodeTotalWorkrate, gonnaGrow);
// getMutator().waitForAllTransitionsComplete();
if (!balanced || BALANCE_COLD_PULLS_IN_SAME_RUN_AS_HOT_PUSHES) {
balanced |= balanceItemsOnColdNode(questionedNode, questionedNodeTotalWorkrate, gonnaGrow);
// getMutator().waitForAllTransitionsComplete();
}
if (balanced)
return true;
if (LOG.isDebugEnabled()) {
LOG.debug( MessageFormat.format(
"policy "+getDataProvider().getName()+" not balancing "+questionedNode+"; " +
"its workrate {0,number,#.##} is acceptable (or cannot be balanced)", questionedNodeTotalWorkrate) );
}
return false;
}
protected boolean balanceItemsOnHotNode(NodeType node, double nodeWorkrate, boolean gonnaGrow) {
double originalNodeWorkrate = nodeWorkrate;
int migrationCount = 0;
int iterationCount = 0;
Set itemsMoved = new LinkedHashSet();
Set nodesChecked = new LinkedHashSet();
// if (nodeFinder.config.COUNT_BACKLOG_AS_EXTRA_WORKRATE) {
// int backlog = nodeFinder.getBacklogQueueLength(questionedNode);
// if (backlog>0) {
// Level l = backlog>1000 ? Level.INFO : backlog>10 ? Level.FINE : Level.FINER;
// if (LOG.isLoggable(l)) {
// LOG.log( l, MessageFormat.format(
// "policy "+getDataProvider().getAbbr()+" detected queue at node "+questionedNode+", " +
// "inflating workrate {0,number,#.##} + "+backlog, questionedNodeTotalWorkrate) );
// }
// questionedNodeTotalWorkrate += backlog;
// }
// }
Double highThreshold = model.getHighThreshold(node);
if (highThreshold == -1) {
// node presumably has been removed; TODO log
return false;
}
while (nodeWorkrate > highThreshold && migrationCount < getMaxMigrationsPerBalancingNode()) {
iterationCount++;
if (LOG.isDebugEnabled()) {
LOG.debug(MessageFormat.format(
"policy "+getDataProvider().getName()+" considering balancing hot node "+node+" " +
"(workrate {0,number,#.##}); iteration "+iterationCount, nodeWorkrate) );
}
// move from hot node, to coldest
NodeType coldNode = helper.findColdestContainer(nodesChecked);
if (coldNode == null) {
if (LOG.isDebugEnabled()) {
LOG.debug( MessageFormat.format(
"policy "+getDataProvider().getName()+" not balancing hot node "+node+" " +
"(workrate {0,number,#.##}); no coldest node available", nodeWorkrate) );
}
break;
}
if (coldNode.equals(node)) {
if (LOG.isDebugEnabled()) {
LOG.debug( MessageFormat.format(
"policy "+getDataProvider().getName()+" not balancing hot node "+node+" " +
"(workrate {0,number,#.##}); it is also the coldest modifiable node", nodeWorkrate) );
}
break;
}
double coldNodeWorkrate = getDataProvider().getTotalWorkrate(coldNode);
boolean emergencyLoadBalancing = coldNodeWorkrate < nodeWorkrate*2/3;
double coldNodeHighThreshold = model.getHighThreshold(coldNode);
if (coldNodeWorkrate >= coldNodeHighThreshold && !emergencyLoadBalancing) {
//don't balance if all nodes are approx equally hot (and very hot)
//for now, stop warning if it is a recurring theme!
// Level level = loggedColdestTooHigh ? Level.FINER : Level.INFO;
// LOG.log(level, MessageFormat.format(
// "policy "+getDataProvider().getAbbr()+" not balancing hot node "+questionedNode+" " +
// "(workrate {0,number,#.##}); coldest node "+coldNode+" has workrate {1,number,#.##} also too high"+
// (loggedColdestTooHigh ? "" : " (future cases will be logged at finer)"),
// questionedNodeTotalWorkrate, coldNodeWorkrate) );
// loggedColdestTooHigh = true;
break;
}
double poolLowWatermark = Double.MAX_VALUE; // TODO
if (gonnaGrow && (coldNodeWorkrate >= poolLowWatermark && !emergencyLoadBalancing)) {
//if we're growing the pool, refuse to balance unless the cold node is indeed very cold, or hot node very hot
//for now, stop warning if it is a recurring theme!
// Level level = loggedColdestTooHigh ? Level.FINER : Level.INFO;
// LOG.log(level, MessageFormat.format(
// "policy "+getDataProvider().getAbbr()+" not balancing hot node "+questionedNode+" " +
// "(workrate {0,number,#.##}); coldest node "+coldNode+" has workrate {1,number,#.##} also too high to accept while pool is growing" +
// (loggedColdestTooHigh ? "" : " (future cases will be logged at finer)"),
// questionedNodeTotalWorkrate, coldNodeWorkrate) );
// loggedColdestTooHigh = true;
break;
}
String questionedNodeName = getDataProvider().getName(node);
String coldNodeName = getDataProvider().getName(coldNode);
Location coldNodeLocation = getDataProvider().getLocation(coldNode);
if (LOG.isDebugEnabled()) {
LOG.debug( MessageFormat.format(
"policy "+getDataProvider().getName()+" balancing hot node "+questionedNodeName+" " +
"("+node+", workrate {0,number,#.##}), " +
"considering target "+coldNodeName+" ("+coldNode+", workrate {1,number,#.##})",
nodeWorkrate, coldNodeWorkrate) );
}
double idealSizeToMove = (nodeWorkrate - coldNodeWorkrate) / 2;
//if the 'ideal' amount to move would cause cold to be too hot, then reduce ideal amount
if (idealSizeToMove + coldNodeWorkrate > coldNodeHighThreshold)
idealSizeToMove = coldNodeHighThreshold - coldNodeWorkrate;
double maxSizeToMoveIdeally = Math.min(
nodeWorkrate/2 + 0.00001,
//permit it to exceed node high if there is no alternative (this is 'max' not 'ideal'),
//so long as it still gives a significant benefit
// getConfiguration().nodeHighWaterMark - coldNodeWorkrate,
(nodeWorkrate - coldNodeWorkrate)*0.9);
double maxSizeToMoveIfNoSmallButLarger = nodeWorkrate*3/4;
Map questionedNodeItems = getDataProvider().getItemWorkrates(node);
if (questionedNodeItems == null) {
if (LOG.isDebugEnabled())
LOG.debug(MessageFormat.format(
"policy "+getDataProvider().getName()+" balancing hot node "+questionedNodeName+" " +
"("+node+", workrate {0,number,#.##}), abandoned; " +
"item report for " + questionedNodeName + " unavailable",
nodeWorkrate));
break;
}
ItemType itemToMove = findBestItemToMove(questionedNodeItems, idealSizeToMove, maxSizeToMoveIdeally,
maxSizeToMoveIfNoSmallButLarger, itemsMoved, coldNodeLocation);
if (itemToMove == null) {
if (LOG.isDebugEnabled())
LOG.debug(MessageFormat.format(
"policy "+getDataProvider().getName()+" balancing hot node "+questionedNodeName+" " +
"("+node+", workrate {0,number,#.##}), ending; " +
"no suitable segment found " +
"(ideal transition item size {1,number,#.##}, max {2,number,#.##}, " +
"moving to coldest node "+coldNodeName+" ("+coldNode+", workrate {3,number,#.##}); available items: {4}",
nodeWorkrate, idealSizeToMove, maxSizeToMoveIdeally, coldNodeWorkrate, questionedNodeItems) );
break;
}
itemsMoved.add(itemToMove);
double itemWorkrate = questionedNodeItems.get(itemToMove);
// if (LOG.isLoggable(Level.FINE))
// LOG.fine( MessageFormat.format(
// "policy "+getDataProvider().getAbbr()+" balancing hot node "+questionedNodeName+" " +
// "(workrate {0,number,#.##}, too high), transitioning " + itemToMove +
// " to "+coldNodeName+" (workrate {1,number,#.##}, now += {2,number,#.##})",
// questionedNodeTotalWorkrate, coldNodeWorkrate, segmentRate) );
nodeWorkrate -= itemWorkrate;
coldNodeWorkrate += itemWorkrate;
moveItem(itemToMove, node, coldNode);
++migrationCount;
}
if (LOG.isDebugEnabled()) {
if (iterationCount == 0) {
if (LOG.isTraceEnabled())
LOG.trace( MessageFormat.format(
"policy "+getDataProvider().getName()+" balancing if hot finished at node "+node+"; " +
"workrate {0,number,#.##} not hot",
originalNodeWorkrate) );
}
else if (itemsMoved.isEmpty()) {
if (LOG.isTraceEnabled())
LOG.trace( MessageFormat.format(
"policy "+getDataProvider().getName()+" balancing finished at hot node "+node+" " +
"(workrate {0,number,#.##}); no way to improve it",
originalNodeWorkrate) );
} else {
LOG.debug( MessageFormat.format(
"policy "+getDataProvider().getName()+" balancing finished at hot node "+node+"; " +
"workrate from {0,number,#.##} to {1,number,#.##} (report now says {2,number,#.##}) " +
"by moving off {3}",
originalNodeWorkrate,
nodeWorkrate,
getDataProvider().getTotalWorkrate(node),
itemsMoved
) );
}
}
return !itemsMoved.isEmpty();
}
protected boolean balanceItemsOnColdNode(NodeType questionedNode, double questionedNodeTotalWorkrate, boolean gonnaGrow) {
// Abort if the node has pending adjustments.
Map items = getDataProvider().getItemWorkrates(questionedNode);
if (items == null) {
if (LOG.isDebugEnabled()) {
LOG.debug( MessageFormat.format(
"policy "+getDataProvider().getName()+" not balancing cold node "+questionedNode+" " +
"(workrate {0,number,#.##}); workrate breakdown unavailable (probably reverting)",
questionedNodeTotalWorkrate) );
}
return false;
}
for (ItemType item : items.keySet()) {
if (!model.isItemMoveable(item)) {
if (LOG.isDebugEnabled()) {
LOG.debug( MessageFormat.format(
"policy "+getDataProvider().getName()+" not balancing cold node "+questionedNode+" " +
"(workrate {0,number,#.##}); at least one item ("+item+") is in flux",
questionedNodeTotalWorkrate) );
}
return false;
}
}
double originalQuestionedNodeTotalWorkrate = questionedNodeTotalWorkrate;
int numMigrations = 0;
Set itemsMoved = new LinkedHashSet();
Set nodesChecked = new LinkedHashSet();
int iters = 0;
Location questionedLocation = getDataProvider().getLocation(questionedNode);
double lowThreshold = model.getLowThreshold(questionedNode);
while (questionedNodeTotalWorkrate < lowThreshold) {
iters++;
if (LOG.isDebugEnabled()) {
LOG.debug( MessageFormat.format(
"policy "+getDataProvider().getName()+" considering balancing cold node "+questionedNode+" " +
"(workrate {0,number,#.##}); iteration "+iters, questionedNodeTotalWorkrate));
}
// move from cold node, to hottest
NodeType hotNode = helper.findHottestContainer(nodesChecked);
if (hotNode == null) {
if (LOG.isDebugEnabled()) {
LOG.debug( MessageFormat.format(
"policy "+getDataProvider().getName()+" not balancing cold node "+questionedNode+" " +
"(workrate {0,number,#.##}); no hottest node available", questionedNodeTotalWorkrate) );
}
break;
}
if (hotNode.equals(questionedNode)) {
if (LOG.isDebugEnabled()) {
LOG.debug( MessageFormat.format(
"policy "+getDataProvider().getName()+" not balancing cold node "+questionedNode+" " +
"(workrate {0,number,#.##}); it is also the hottest modfiable node", questionedNodeTotalWorkrate) );
}
break;
}
double hotNodeWorkrate = getDataProvider().getTotalWorkrate(hotNode);
double hotNodeLowThreshold = model.getLowThreshold(hotNode);
double hotNodeHighThreshold = model.getHighThreshold(hotNode);
boolean emergencyLoadBalancing = false; //doesn't apply to cold
if (hotNodeWorkrate == -1 || hotNodeLowThreshold == -1 || hotNodeHighThreshold == -1) {
// hotNode presumably has been removed; TODO log
break;
}
if (hotNodeWorkrate <= hotNodeLowThreshold && !emergencyLoadBalancing) {
//don't balance if all nodes are too low
//for now, stop warning if it is a recurring theme!
// Level level = loggedHottestTooLow ? Level.FINER : Level.INFO;
// LOG.log(level, MessageFormat.format(
// "policy "+getDataProvider().getAbbr()+" not balancing cold node "+questionedNode+" " +
// "(workrate {0,number,#.##}); hottest node "+hotNode+" has workrate {1,number,#.##} also too low" +
// (loggedHottestTooLow ? "" : " (future cases will be logged at finer)"),
// questionedNodeTotalWorkrate, hotNodeWorkrate) );
// loggedHottestTooLow = true;
break;
}
if (gonnaGrow && (hotNodeWorkrate <= hotNodeHighThreshold && !emergencyLoadBalancing)) {
//if we're growing the pool, refuse to balance unless the hot node is quite hot
//again, stop warning if it is a recurring theme!
// Level level = loggedHottestTooLow ? Level.FINER : Level.INFO;
// LOG.log(level, MessageFormat.format(
// "policy "+getDataProvider().getAbbr()+" not balancing cold node "+questionedNode+" " +
// "(workrate {0,number,#.##}); hottest node "+hotNode+" has workrate {1,number,#.##} also too low to accept while pool is growing"+
// (loggedHottestTooLow ? "" : " (future cases will be logged at finer)"),
// questionedNodeTotalWorkrate, hotNodeWorkrate) );
// loggedHottestTooLow = true;
break;
}
String questionedNodeName = getDataProvider().getName(questionedNode);
String hotNodeName = getDataProvider().getName(hotNode);
if (LOG.isDebugEnabled()) {
LOG.debug( MessageFormat.format(
"policy "+getDataProvider().getName()+" balancing cold node "+questionedNodeName+" " +
"("+questionedNode+", workrate {0,number,#.##}), " +
"considering source "+hotNodeName+" ("+hotNode+", workrate {1,number,#.##})",
questionedNodeTotalWorkrate, hotNodeWorkrate) );
}
double idealSizeToMove = (hotNodeWorkrate - questionedNodeTotalWorkrate) / 2;
//if the 'ideal' amount to move would cause cold to be too hot, then reduce ideal amount
double targetNodeHighThreshold = model.getHighThreshold(questionedNode);
if (idealSizeToMove + questionedNodeTotalWorkrate > targetNodeHighThreshold)
idealSizeToMove = targetNodeHighThreshold - questionedNodeTotalWorkrate;
double maxSizeToMoveIdeally = Math.min(
hotNodeWorkrate/2,
//allow to swap order, but not very much (0.9 was allowed when balancing high)
(hotNodeWorkrate - questionedNodeTotalWorkrate)*0.6);
double maxSizeToMoveIfNoSmallButLarger = questionedNodeTotalWorkrate*3/4;
Map hotNodeItems = getDataProvider().getItemWorkrates(hotNode);
if (hotNodeItems == null) {
if (LOG.isDebugEnabled())
LOG.debug(MessageFormat.format(
"policy "+getDataProvider().getName()+" balancing cold node "+questionedNodeName+" " +
"("+questionedNode+", workrate {0,number,#.##}), " +
"excluding hot node "+hotNodeName+" because its item report unavailable",
questionedNodeTotalWorkrate));
nodesChecked.add(hotNode);
continue;
}
ItemType itemToMove = findBestItemToMove(hotNodeItems, idealSizeToMove, maxSizeToMoveIdeally,
maxSizeToMoveIfNoSmallButLarger, itemsMoved, questionedLocation);
if (itemToMove == null) {
if (LOG.isDebugEnabled())
LOG.debug(MessageFormat.format(
"policy "+getDataProvider().getName()+" balancing cold node "+questionedNodeName+" " +
"("+questionedNode+", workrate {0,number,#.##}), " +
"excluding hot node "+hotNodeName+" because it has no appilcable items " +
"(ideal transition item size {1,number,#.##}, max {2,number,#.##}, " +
"moving from hot node "+hotNodeName+" ("+hotNode+", workrate {3,number,#.##}); available items: {4}",
questionedNodeTotalWorkrate, idealSizeToMove, maxSizeToMoveIdeally, hotNodeWorkrate, hotNodeItems) );
nodesChecked.add(hotNode);
continue;
}
itemsMoved.add(itemToMove);
double segmentRate = hotNodeItems.get(itemToMove);
// if (LOG.isLoggable(Level.FINE))
// LOG.fine( MessageFormat.format(
// "policy "+getDataProvider().getAbbr()+" balancing cold node "+questionedNodeName+" " +
// "(workrate {0,number,#.##}, too low), transitioning " + itemToMove +
// " from "+hotNodeName+" (workrate {1,number,#.##}, now -= {2,number,#.##})",
// questionedNodeTotalWorkrate, hotNodeWorkrate, segmentRate) );
questionedNodeTotalWorkrate += segmentRate;
hotNodeWorkrate -= segmentRate;
moveItem(itemToMove, hotNode, questionedNode);
if (++numMigrations >= getMaxMigrationsPerBalancingNode()) {
break;
}
}
if (LOG.isDebugEnabled()) {
if (iters == 0) {
if (LOG.isTraceEnabled())
LOG.trace( MessageFormat.format(
"policy "+getDataProvider().getName()+" balancing if cold finished at node "+questionedNode+"; " +
"workrate {0,number,#.##} not cold",
originalQuestionedNodeTotalWorkrate) );
}
else if (itemsMoved.isEmpty()) {
if (LOG.isTraceEnabled())
LOG.trace( MessageFormat.format(
"policy "+getDataProvider().getName()+" balancing finished at cold node "+questionedNode+" " +
"(workrate {0,number,#.##}); no way to improve it",
originalQuestionedNodeTotalWorkrate) );
} else {
LOG.debug( MessageFormat.format(
"policy "+getDataProvider().getName()+" balancing finished at cold node "+questionedNode+"; " +
"workrate from {0,number,#.##} to {1,number,#.##} (report now says {2,number,#.##}) " +
"by moving in {3}",
originalQuestionedNodeTotalWorkrate,
questionedNodeTotalWorkrate,
getDataProvider().getTotalWorkrate(questionedNode),
itemsMoved) );
}
}
return !itemsMoved.isEmpty();
}
protected void moveItem(ItemType item, NodeType oldNode, NodeType newNode) {
item.move(newNode);
model.onItemMoved(item, newNode);
}
/**
* "Best" is defined as nearest to the targetCost, without exceeding maxCost, unless maxCostIfNothingSmallerButLarger > 0
* which does just that (useful if the ideal and target are estimates and aren't quite right, typically it will take
* something larger than maxRate but less than half the total rate, which is only possible when the estimates don't agree)
*/
protected ItemType findBestItemToMove(Map costsPerItem, double targetCost, double maxCost,
double maxCostIfNothingSmallerButLarger, Set excludedItems, Location locationIfKnown) {
ItemType closestMatch = null;
ItemType smallestMoveable = null, largest = null;
double minDiff = Double.MAX_VALUE, smallestC = Double.MAX_VALUE, largestC = Double.MIN_VALUE;
boolean exclusions = false;
for (Entry entry : costsPerItem.entrySet()) {
ItemType item = entry.getKey();
Double cost = entry.getValue();
if (cost == null) {
if (LOG.isDebugEnabled()) LOG.debug(MessageFormat.format("Item ''{0}'' has null workrate: skipping", item));
continue;
}
if (!model.isItemMoveable(item)) {
if (LOG.isDebugEnabled()) LOG.debug(MessageFormat.format("Item ''{0}'' cannot be moved: skipping", item));
continue;
}
if (cost < 0) {
if (LOG.isDebugEnabled()) LOG.debug(MessageFormat.format("Item ''{0}'' subject to recent adjustment: skipping", item));
continue;
}
if (excludedItems.contains(item)) {
exclusions = true;
continue;
}
if (cost < 0) { // FIXME: already tested above
exclusions = true;
continue;
}
if (cost <= 0) { // FIXME: overlaps previous condition
continue;
}
if (largest == null || cost > largestC) {
largest = item;
largestC = cost;
}
if (!model.isItemMoveable(item)) { // FIXME: already tested above
continue;
}
if (locationIfKnown != null && !model.isItemAllowedIn(item, locationIfKnown)) {
continue;
}
if (smallestMoveable == null || cost < smallestC) {
smallestMoveable = item;
smallestC = cost;
}
if (cost > maxCost) {
continue;
}
double diff = Math.abs(targetCost - cost);
if (closestMatch == null || diff < minDiff) {
closestMatch = item;
minDiff = diff;
}
}
if (closestMatch != null)
return closestMatch;
if (smallestC < maxCostIfNothingSmallerButLarger && smallestC < largestC && !exclusions)
return smallestMoveable;
return null;
}
}
