org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of hbase-server Show documentation
Show all versions of hbase-server Show documentation
Server functionality for HBase
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hbase.master.balancer;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Deque;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Random;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.ClusterMetrics;
import org.apache.hadoop.hbase.HBaseInterfaceAudience;
import org.apache.hadoop.hbase.RegionMetrics;
import org.apache.hadoop.hbase.ServerMetrics;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.RegionInfo;
import org.apache.hadoop.hbase.master.MasterServices;
import org.apache.hadoop.hbase.master.RegionPlan;
import org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer.Cluster.Action;
import org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer.Cluster.Action.Type;
import org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer.Cluster.AssignRegionAction;
import org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer.Cluster.LocalityType;
import org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer.Cluster.MoveRegionAction;
import org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer.Cluster.SwapRegionsAction;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hbase.thirdparty.com.google.common.annotations.VisibleForTesting;
import org.apache.hbase.thirdparty.com.google.common.base.Optional;
import org.apache.hbase.thirdparty.com.google.common.collect.Lists;
/**
* This is a best effort load balancer. Given a Cost function F(C) => x It will
* randomly try and mutate the cluster to Cprime. If F(Cprime) < F(C) then the
* new cluster state becomes the plan. It includes costs functions to compute the cost of:
*
* - Region Load
* - Table Load
* - Data Locality
* - Memstore Sizes
* - Storefile Sizes
*
*
*
* Every cost function returns a number between 0 and 1 inclusive; where 0 is the lowest cost
* best solution, and 1 is the highest possible cost and the worst solution. The computed costs are
* scaled by their respective multipliers:
*
*
* - hbase.master.balancer.stochastic.regionLoadCost
* - hbase.master.balancer.stochastic.moveCost
* - hbase.master.balancer.stochastic.tableLoadCost
* - hbase.master.balancer.stochastic.localityCost
* - hbase.master.balancer.stochastic.memstoreSizeCost
* - hbase.master.balancer.stochastic.storefileSizeCost
*
*
* In addition to the above configurations, the balancer can be tuned by the following
* configuration values:
*
* - hbase.master.balancer.stochastic.maxMoveRegions which
* controls what the max number of regions that can be moved in a single invocation of this
* balancer.
* - hbase.master.balancer.stochastic.stepsPerRegion is the coefficient by which the number of
* regions is multiplied to try and get the number of times the balancer will
* mutate all servers.
* - hbase.master.balancer.stochastic.maxSteps which controls the maximum number of times that
* the balancer will try and mutate all the servers. The balancer will use the minimum of this
* value and the above computation.
*
*
* This balancer is best used with hbase.master.loadbalance.bytable set to false
* so that the balancer gets the full picture of all loads on the cluster.
*/
@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
@edu.umd.cs.findbugs.annotations.SuppressWarnings(value="IS2_INCONSISTENT_SYNC",
justification="Complaint is about costFunctions not being synchronized; not end of the world")
public class StochasticLoadBalancer extends BaseLoadBalancer {
protected static final String STEPS_PER_REGION_KEY =
"hbase.master.balancer.stochastic.stepsPerRegion";
protected static final String MAX_STEPS_KEY =
"hbase.master.balancer.stochastic.maxSteps";
protected static final String RUN_MAX_STEPS_KEY =
"hbase.master.balancer.stochastic.runMaxSteps";
protected static final String MAX_RUNNING_TIME_KEY =
"hbase.master.balancer.stochastic.maxRunningTime";
protected static final String KEEP_REGION_LOADS =
"hbase.master.balancer.stochastic.numRegionLoadsToRemember";
private static final String TABLE_FUNCTION_SEP = "_";
protected static final String MIN_COST_NEED_BALANCE_KEY =
"hbase.master.balancer.stochastic.minCostNeedBalance";
protected static final Random RANDOM = new Random(System.currentTimeMillis());
private static final Logger LOG = LoggerFactory.getLogger(StochasticLoadBalancer.class);
Map> loads = new HashMap<>();
// values are defaults
private int maxSteps = 1000000;
private boolean runMaxSteps = false;
private int stepsPerRegion = 800;
private long maxRunningTime = 30 * 1000 * 1; // 30 seconds.
private int numRegionLoadsToRemember = 15;
private float minCostNeedBalance = 0.05f;
private List candidateGenerators;
private CostFromRegionLoadFunction[] regionLoadFunctions;
private CostFunction[] costFunctions; // FindBugs: Wants this protected; IS2_INCONSISTENT_SYNC
// to save and report costs to JMX
private Double curOverallCost = 0d;
private Double[] tempFunctionCosts;
private Double[] curFunctionCosts;
// Keep locality based picker and cost function to alert them
// when new services are offered
private LocalityBasedCandidateGenerator localityCandidateGenerator;
private ServerLocalityCostFunction localityCost;
private RackLocalityCostFunction rackLocalityCost;
private RegionReplicaHostCostFunction regionReplicaHostCostFunction;
private RegionReplicaRackCostFunction regionReplicaRackCostFunction;
/**
* The constructor that pass a MetricsStochasticBalancer to BaseLoadBalancer to replace its
* default MetricsBalancer
*/
public StochasticLoadBalancer() {
super(new MetricsStochasticBalancer());
}
@Override
public void onConfigurationChange(Configuration conf) {
setConf(conf);
}
@Override
public synchronized void setConf(Configuration conf) {
super.setConf(conf);
maxSteps = conf.getInt(MAX_STEPS_KEY, maxSteps);
stepsPerRegion = conf.getInt(STEPS_PER_REGION_KEY, stepsPerRegion);
maxRunningTime = conf.getLong(MAX_RUNNING_TIME_KEY, maxRunningTime);
runMaxSteps = conf.getBoolean(RUN_MAX_STEPS_KEY, runMaxSteps);
numRegionLoadsToRemember = conf.getInt(KEEP_REGION_LOADS, numRegionLoadsToRemember);
minCostNeedBalance = conf.getFloat(MIN_COST_NEED_BALANCE_KEY, minCostNeedBalance);
if (localityCandidateGenerator == null) {
localityCandidateGenerator = new LocalityBasedCandidateGenerator(services);
}
localityCost = new ServerLocalityCostFunction(conf, services);
rackLocalityCost = new RackLocalityCostFunction(conf, services);
if (this.candidateGenerators == null) {
candidateGenerators = Lists.newArrayList();
candidateGenerators.add(new RandomCandidateGenerator());
candidateGenerators.add(new LoadCandidateGenerator());
candidateGenerators.add(localityCandidateGenerator);
candidateGenerators.add(new RegionReplicaRackCandidateGenerator());
}
regionLoadFunctions = new CostFromRegionLoadFunction[] {
new ReadRequestCostFunction(conf),
new WriteRequestCostFunction(conf),
new MemStoreSizeCostFunction(conf),
new StoreFileCostFunction(conf)
};
regionReplicaHostCostFunction = new RegionReplicaHostCostFunction(conf);
regionReplicaRackCostFunction = new RegionReplicaRackCostFunction(conf);
costFunctions = new CostFunction[]{
new RegionCountSkewCostFunction(conf),
new PrimaryRegionCountSkewCostFunction(conf),
new MoveCostFunction(conf),
localityCost,
rackLocalityCost,
new TableSkewCostFunction(conf),
regionReplicaHostCostFunction,
regionReplicaRackCostFunction,
regionLoadFunctions[0],
regionLoadFunctions[1],
regionLoadFunctions[2],
regionLoadFunctions[3],
};
curFunctionCosts= new Double[costFunctions.length];
tempFunctionCosts= new Double[costFunctions.length];
LOG.info("Loaded config; maxSteps=" + maxSteps + ", stepsPerRegion=" + stepsPerRegion +
", maxRunningTime=" + maxRunningTime + ", isByTable=" + isByTable + ", etc.");
}
protected void setCandidateGenerators(List customCandidateGenerators) {
this.candidateGenerators = customCandidateGenerators;
}
@Override
protected void setSlop(Configuration conf) {
this.slop = conf.getFloat("hbase.regions.slop", 0.001F);
}
@Override
public synchronized void setClusterMetrics(ClusterMetrics st) {
super.setClusterMetrics(st);
updateRegionLoad();
for(CostFromRegionLoadFunction cost : regionLoadFunctions) {
cost.setClusterMetrics(st);
}
// update metrics size
try {
// by-table or ensemble mode
int tablesCount = isByTable ? services.getTableDescriptors().getAll().size() : 1;
int functionsCount = getCostFunctionNames().length;
updateMetricsSize(tablesCount * (functionsCount + 1)); // +1 for overall
} catch (Exception e) {
LOG.error("failed to get the size of all tables", e);
}
}
/**
* Update the number of metrics that are reported to JMX
*/
public void updateMetricsSize(int size) {
if (metricsBalancer instanceof MetricsStochasticBalancer) {
((MetricsStochasticBalancer) metricsBalancer).updateMetricsSize(size);
}
}
@Override
public synchronized void setMasterServices(MasterServices masterServices) {
super.setMasterServices(masterServices);
this.localityCost.setServices(masterServices);
this.rackLocalityCost.setServices(masterServices);
this.localityCandidateGenerator.setServices(masterServices);
}
@Override
protected synchronized boolean areSomeRegionReplicasColocated(Cluster c) {
regionReplicaHostCostFunction.init(c);
if (regionReplicaHostCostFunction.cost() > 0) return true;
regionReplicaRackCostFunction.init(c);
if (regionReplicaRackCostFunction.cost() > 0) return true;
return false;
}
@Override
protected boolean needsBalance(TableName tableName, Cluster cluster) {
ClusterLoadState cs = new ClusterLoadState(cluster.clusterState);
if (cs.getNumServers() < MIN_SERVER_BALANCE) {
if (LOG.isDebugEnabled()) {
LOG.debug("Not running balancer because only " + cs.getNumServers()
+ " active regionserver(s)");
}
return false;
}
if (areSomeRegionReplicasColocated(cluster)) {
return true;
}
double total = 0.0;
float sumMultiplier = 0.0f;
for (CostFunction c : costFunctions) {
float multiplier = c.getMultiplier();
if (multiplier <= 0) {
LOG.trace("{} not needed because multiplier is <= 0", c.getClass().getSimpleName());
continue;
}
if (!c.isNeeded()) {
LOG.trace("{} not needed", c.getClass().getSimpleName());
continue;
}
sumMultiplier += multiplier;
total += c.cost() * multiplier;
}
boolean balanced = total <= 0 || sumMultiplier <= 0 ||
(sumMultiplier > 0 && (total / sumMultiplier) < minCostNeedBalance);
if (LOG.isDebugEnabled()) {
LOG.debug("{} {}; total cost={}, sum multiplier={}; cost/multiplier to need a balance is {}",
balanced ? "Skipping load balancing because balanced" : "We need to load balance",
isByTable ? String.format("table (%s)", tableName) : "cluster",
total, sumMultiplier, minCostNeedBalance);
if (LOG.isTraceEnabled()) {
LOG.trace("Balance decision detailed function costs={}", functionCost());
}
}
return !balanced;
}
@VisibleForTesting
Cluster.Action nextAction(Cluster cluster) {
return candidateGenerators.get(RANDOM.nextInt(candidateGenerators.size()))
.generate(cluster);
}
/**
* Given the cluster state this will try and approach an optimal balance. This
* should always approach the optimal state given enough steps.
*/
@Override
public synchronized List balanceTable(TableName tableName, Map> loadOfOneTable) {
List plans = balanceMasterRegions(loadOfOneTable);
if (plans != null || loadOfOneTable == null || loadOfOneTable.size() <= 1) {
return plans;
}
if (masterServerName != null && loadOfOneTable.containsKey(masterServerName)) {
if (loadOfOneTable.size() <= 2) {
return null;
}
loadOfOneTable = new HashMap<>(loadOfOneTable);
loadOfOneTable.remove(masterServerName);
}
// On clusters with lots of HFileLinks or lots of reference files,
// instantiating the storefile infos can be quite expensive.
// Allow turning this feature off if the locality cost is not going to
// be used in any computations.
RegionLocationFinder finder = null;
if ((this.localityCost != null && this.localityCost.getMultiplier() > 0)
|| (this.rackLocalityCost != null && this.rackLocalityCost.getMultiplier() > 0)) {
finder = this.regionFinder;
}
//The clusterState that is given to this method contains the state
//of all the regions in the table(s) (that's true today)
// Keep track of servers to iterate through them.
Cluster cluster = new Cluster(loadOfOneTable, loads, finder, rackManager);
long startTime = EnvironmentEdgeManager.currentTime();
initCosts(cluster);
if (!needsBalance(tableName, cluster)) {
return null;
}
double currentCost = computeCost(cluster, Double.MAX_VALUE);
curOverallCost = currentCost;
for (int i = 0; i < this.curFunctionCosts.length; i++) {
curFunctionCosts[i] = tempFunctionCosts[i];
}
double initCost = currentCost;
double newCost = currentCost;
long computedMaxSteps;
if (runMaxSteps) {
computedMaxSteps = Math.max(this.maxSteps,
((long)cluster.numRegions * (long)this.stepsPerRegion * (long)cluster.numServers));
} else {
long calculatedMaxSteps = (long)cluster.numRegions * (long)this.stepsPerRegion *
(long)cluster.numServers;
computedMaxSteps = Math.min(this.maxSteps, calculatedMaxSteps);
if (calculatedMaxSteps > maxSteps) {
LOG.warn("calculatedMaxSteps:{} for loadbalancer's stochastic walk is larger than "
+ "maxSteps:{}. Hence load balancing may not work well. Setting parameter "
+ "\"hbase.master.balancer.stochastic.runMaxSteps\" to true can overcome this issue."
+ "(This config change does not require service restart)", calculatedMaxSteps,
maxRunningTime);
}
}
LOG.info("start StochasticLoadBalancer.balancer, initCost=" + currentCost + ", functionCost="
+ functionCost() + " computedMaxSteps: " + computedMaxSteps);
// Perform a stochastic walk to see if we can get a good fit.
long step;
for (step = 0; step < computedMaxSteps; step++) {
Cluster.Action action = nextAction(cluster);
if (action.type == Type.NULL) {
continue;
}
cluster.doAction(action);
updateCostsWithAction(cluster, action);
newCost = computeCost(cluster, currentCost);
// Should this be kept?
if (newCost < currentCost) {
currentCost = newCost;
// save for JMX
curOverallCost = currentCost;
for (int i = 0; i < this.curFunctionCosts.length; i++) {
curFunctionCosts[i] = tempFunctionCosts[i];
}
} else {
// Put things back the way they were before.
// TODO: undo by remembering old values
Action undoAction = action.undoAction();
cluster.doAction(undoAction);
updateCostsWithAction(cluster, undoAction);
}
if (EnvironmentEdgeManager.currentTime() - startTime >
maxRunningTime) {
break;
}
}
long endTime = EnvironmentEdgeManager.currentTime();
metricsBalancer.balanceCluster(endTime - startTime);
// update costs metrics
updateStochasticCosts(tableName, curOverallCost, curFunctionCosts);
if (initCost > currentCost) {
plans = createRegionPlans(cluster);
LOG.info("Finished computing new load balance plan. Computation took {}" +
" to try {} different iterations. Found a solution that moves " +
"{} regions; Going from a computed cost of {}" +
" to a new cost of {}", java.time.Duration.ofMillis(endTime - startTime),
step, plans.size(), initCost, currentCost);
return plans;
}
LOG.info("Could not find a better load balance plan. Tried {} different configurations in " +
"{}, and did not find anything with a computed cost less than {}", step,
java.time.Duration.ofMillis(endTime - startTime), initCost);
return null;
}
/**
* update costs to JMX
*/
private void updateStochasticCosts(TableName tableName, Double overall, Double[] subCosts) {
if (tableName == null) return;
// check if the metricsBalancer is MetricsStochasticBalancer before casting
if (metricsBalancer instanceof MetricsStochasticBalancer) {
MetricsStochasticBalancer balancer = (MetricsStochasticBalancer) metricsBalancer;
// overall cost
balancer.updateStochasticCost(tableName.getNameAsString(),
"Overall", "Overall cost", overall);
// each cost function
for (int i = 0; i < costFunctions.length; i++) {
CostFunction costFunction = costFunctions[i];
String costFunctionName = costFunction.getClass().getSimpleName();
Double costPercent = (overall == 0) ? 0 : (subCosts[i] / overall);
// TODO: cost function may need a specific description
balancer.updateStochasticCost(tableName.getNameAsString(), costFunctionName,
"The percent of " + costFunctionName, costPercent);
}
}
}
private String functionCost() {
StringBuilder builder = new StringBuilder();
for (CostFunction c:costFunctions) {
builder.append(c.getClass().getSimpleName());
builder.append(" : (");
builder.append(c.getMultiplier());
builder.append(", ");
builder.append(c.cost());
builder.append("); ");
}
return builder.toString();
}
/**
* Create all of the RegionPlan's needed to move from the initial cluster state to the desired
* state.
*
* @param cluster The state of the cluster
* @return List of RegionPlan's that represent the moves needed to get to desired final state.
*/
private List createRegionPlans(Cluster cluster) {
List plans = new LinkedList<>();
for (int regionIndex = 0;
regionIndex < cluster.regionIndexToServerIndex.length; regionIndex++) {
int initialServerIndex = cluster.initialRegionIndexToServerIndex[regionIndex];
int newServerIndex = cluster.regionIndexToServerIndex[regionIndex];
if (initialServerIndex != newServerIndex) {
RegionInfo region = cluster.regions[regionIndex];
ServerName initialServer = cluster.servers[initialServerIndex];
ServerName newServer = cluster.servers[newServerIndex];
if (LOG.isTraceEnabled()) {
LOG.trace("Moving Region " + region.getEncodedName() + " from server "
+ initialServer.getHostname() + " to " + newServer.getHostname());
}
RegionPlan rp = new RegionPlan(region, initialServer, newServer);
plans.add(rp);
}
}
return plans;
}
/**
* Store the current region loads.
*/
private synchronized void updateRegionLoad() {
// We create a new hashmap so that regions that are no longer there are removed.
// However we temporarily need the old loads so we can use them to keep the rolling average.
Map> oldLoads = loads;
loads = new HashMap<>();
clusterStatus.getLiveServerMetrics().forEach((ServerName sn, ServerMetrics sm) -> {
sm.getRegionMetrics().forEach((byte[] regionName, RegionMetrics rm) -> {
String regionNameAsString = RegionInfo.getRegionNameAsString(regionName);
Deque rLoads = oldLoads.get(regionNameAsString);
if (rLoads == null) {
rLoads = new ArrayDeque<>(numRegionLoadsToRemember + 1);
} else if (rLoads.size() >= numRegionLoadsToRemember) {
rLoads.remove();
}
rLoads.add(new BalancerRegionLoad(rm));
loads.put(regionNameAsString, rLoads);
});
});
for(CostFromRegionLoadFunction cost : regionLoadFunctions) {
cost.setLoads(loads);
}
}
protected void initCosts(Cluster cluster) {
for (CostFunction c:costFunctions) {
c.init(cluster);
}
}
protected void updateCostsWithAction(Cluster cluster, Action action) {
for (CostFunction c : costFunctions) {
c.postAction(action);
}
}
/**
* Get the names of the cost functions
*/
public String[] getCostFunctionNames() {
if (costFunctions == null) return null;
String[] ret = new String[costFunctions.length];
for (int i = 0; i < costFunctions.length; i++) {
CostFunction c = costFunctions[i];
ret[i] = c.getClass().getSimpleName();
}
return ret;
}
/**
* This is the main cost function. It will compute a cost associated with a proposed cluster
* state. All different costs will be combined with their multipliers to produce a double cost.
*
* @param cluster The state of the cluster
* @param previousCost the previous cost. This is used as an early out.
* @return a double of a cost associated with the proposed cluster state. This cost is an
* aggregate of all individual cost functions.
*/
protected double computeCost(Cluster cluster, double previousCost) {
double total = 0;
for (int i = 0; i < costFunctions.length; i++) {
CostFunction c = costFunctions[i];
this.tempFunctionCosts[i] = 0.0;
if (c.getMultiplier() <= 0) {
continue;
}
Float multiplier = c.getMultiplier();
Double cost = c.cost();
this.tempFunctionCosts[i] = multiplier*cost;
total += this.tempFunctionCosts[i];
if (total > previousCost) {
break;
}
}
return total;
}
/** Generates a candidate action to be applied to the cluster for cost function search */
abstract static class CandidateGenerator {
abstract Cluster.Action generate(Cluster cluster);
/**
* From a list of regions pick a random one. Null can be returned which
* {@link StochasticLoadBalancer#balanceCluster(Map)} recognize as signal to try a region move
* rather than swap.
*
* @param cluster The state of the cluster
* @param server index of the server
* @param chanceOfNoSwap Chance that this will decide to try a move rather
* than a swap.
* @return a random {@link RegionInfo} or null if an asymmetrical move is
* suggested.
*/
protected int pickRandomRegion(Cluster cluster, int server, double chanceOfNoSwap) {
// Check to see if this is just a move.
if (cluster.regionsPerServer[server].length == 0 || RANDOM.nextFloat() < chanceOfNoSwap) {
// signal a move only.
return -1;
}
int rand = RANDOM.nextInt(cluster.regionsPerServer[server].length);
return cluster.regionsPerServer[server][rand];
}
protected int pickRandomServer(Cluster cluster) {
if (cluster.numServers < 1) {
return -1;
}
return RANDOM.nextInt(cluster.numServers);
}
protected int pickRandomRack(Cluster cluster) {
if (cluster.numRacks < 1) {
return -1;
}
return RANDOM.nextInt(cluster.numRacks);
}
protected int pickOtherRandomServer(Cluster cluster, int serverIndex) {
if (cluster.numServers < 2) {
return -1;
}
while (true) {
int otherServerIndex = pickRandomServer(cluster);
if (otherServerIndex != serverIndex) {
return otherServerIndex;
}
}
}
protected int pickOtherRandomRack(Cluster cluster, int rackIndex) {
if (cluster.numRacks < 2) {
return -1;
}
while (true) {
int otherRackIndex = pickRandomRack(cluster);
if (otherRackIndex != rackIndex) {
return otherRackIndex;
}
}
}
protected Cluster.Action pickRandomRegions(Cluster cluster,
int thisServer,
int otherServer) {
if (thisServer < 0 || otherServer < 0) {
return Cluster.NullAction;
}
// Decide who is most likely to need another region
int thisRegionCount = cluster.getNumRegions(thisServer);
int otherRegionCount = cluster.getNumRegions(otherServer);
// Assign the chance based upon the above
double thisChance = (thisRegionCount > otherRegionCount) ? 0 : 0.5;
double otherChance = (thisRegionCount <= otherRegionCount) ? 0 : 0.5;
int thisRegion = pickRandomRegion(cluster, thisServer, thisChance);
int otherRegion = pickRandomRegion(cluster, otherServer, otherChance);
return getAction(thisServer, thisRegion, otherServer, otherRegion);
}
protected Cluster.Action getAction(int fromServer, int fromRegion,
int toServer, int toRegion) {
if (fromServer < 0 || toServer < 0) {
return Cluster.NullAction;
}
if (fromRegion > 0 && toRegion > 0) {
return new Cluster.SwapRegionsAction(fromServer, fromRegion,
toServer, toRegion);
} else if (fromRegion > 0) {
return new Cluster.MoveRegionAction(fromRegion, fromServer, toServer);
} else if (toRegion > 0) {
return new Cluster.MoveRegionAction(toRegion, toServer, fromServer);
} else {
return Cluster.NullAction;
}
}
/**
* Returns a random iteration order of indexes of an array with size length
*/
protected List getRandomIterationOrder(int length) {
ArrayList order = new ArrayList<>(length);
for (int i = 0; i < length; i++) {
order.add(i);
}
Collections.shuffle(order);
return order;
}
}
static class RandomCandidateGenerator extends CandidateGenerator {
@Override
Cluster.Action generate(Cluster cluster) {
int thisServer = pickRandomServer(cluster);
// Pick the other server
int otherServer = pickOtherRandomServer(cluster, thisServer);
return pickRandomRegions(cluster, thisServer, otherServer);
}
}
static class LoadCandidateGenerator extends CandidateGenerator {
@Override
Cluster.Action generate(Cluster cluster) {
cluster.sortServersByRegionCount();
int thisServer = pickMostLoadedServer(cluster, -1);
int otherServer = pickLeastLoadedServer(cluster, thisServer);
return pickRandomRegions(cluster, thisServer, otherServer);
}
private int pickLeastLoadedServer(final Cluster cluster, int thisServer) {
Integer[] servers = cluster.serverIndicesSortedByRegionCount;
int index = 0;
while (servers[index] == null || servers[index] == thisServer) {
index++;
if (index == servers.length) {
return -1;
}
}
return servers[index];
}
private int pickMostLoadedServer(final Cluster cluster, int thisServer) {
Integer[] servers = cluster.serverIndicesSortedByRegionCount;
int index = servers.length - 1;
while (servers[index] == null || servers[index] == thisServer) {
index--;
if (index < 0) {
return -1;
}
}
return servers[index];
}
}
static class LocalityBasedCandidateGenerator extends CandidateGenerator {
private MasterServices masterServices;
LocalityBasedCandidateGenerator(MasterServices masterServices) {
this.masterServices = masterServices;
}
@Override
Cluster.Action generate(Cluster cluster) {
if (this.masterServices == null) {
int thisServer = pickRandomServer(cluster);
// Pick the other server
int otherServer = pickOtherRandomServer(cluster, thisServer);
return pickRandomRegions(cluster, thisServer, otherServer);
}
// Randomly iterate through regions until you find one that is not on ideal host
for (int region : getRandomIterationOrder(cluster.numRegions)) {
int currentServer = cluster.regionIndexToServerIndex[region];
if (currentServer != cluster.getOrComputeRegionsToMostLocalEntities(LocalityType.SERVER)[region]) {
Optional potential = tryMoveOrSwap(
cluster,
currentServer,
region,
cluster.getOrComputeRegionsToMostLocalEntities(LocalityType.SERVER)[region]
);
if (potential.isPresent()) {
return potential.get();
}
}
}
return Cluster.NullAction;
}
/**
* Try to generate a move/swap fromRegion between fromServer and toServer such that locality is improved.
* Returns empty optional if no move can be found
*/
private Optional tryMoveOrSwap(Cluster cluster,
int fromServer,
int fromRegion,
int toServer) {
// Try move first. We know apriori fromRegion has the highest locality on toServer
if (cluster.serverHasTooFewRegions(toServer)) {
return Optional.of(getAction(fromServer, fromRegion, toServer, -1));
}
// Compare locality gain/loss from swapping fromRegion with regions on toServer
double fromRegionLocalityDelta =
getWeightedLocality(cluster, fromRegion, toServer) - getWeightedLocality(cluster, fromRegion, fromServer);
for (int toRegionIndex : getRandomIterationOrder(cluster.regionsPerServer[toServer].length)) {
int toRegion = cluster.regionsPerServer[toServer][toRegionIndex];
double toRegionLocalityDelta =
getWeightedLocality(cluster, toRegion, fromServer) - getWeightedLocality(cluster, toRegion, toServer);
// If locality would remain neutral or improve, attempt the swap
if (fromRegionLocalityDelta + toRegionLocalityDelta >= 0) {
return Optional.of(getAction(fromServer, fromRegion, toServer, toRegion));
}
}
return Optional.absent();
}
private double getWeightedLocality(Cluster cluster, int region, int server) {
return cluster.getOrComputeWeightedLocality(region, server, LocalityType.SERVER);
}
void setServices(MasterServices services) {
this.masterServices = services;
}
}
/**
* Generates candidates which moves the replicas out of the region server for
* co-hosted region replicas
*/
static class RegionReplicaCandidateGenerator extends CandidateGenerator {
RandomCandidateGenerator randomGenerator = new RandomCandidateGenerator();
/**
* Randomly select one regionIndex out of all region replicas co-hosted in the same group
* (a group is a server, host or rack)
* @param primariesOfRegionsPerGroup either Cluster.primariesOfRegionsPerServer,
* primariesOfRegionsPerHost or primariesOfRegionsPerRack
* @param regionsPerGroup either Cluster.regionsPerServer, regionsPerHost or regionsPerRack
* @param regionIndexToPrimaryIndex Cluster.regionsIndexToPrimaryIndex
* @return a regionIndex for the selected primary or -1 if there is no co-locating
*/
int selectCoHostedRegionPerGroup(int[] primariesOfRegionsPerGroup, int[] regionsPerGroup
, int[] regionIndexToPrimaryIndex) {
int currentPrimary = -1;
int currentPrimaryIndex = -1;
int selectedPrimaryIndex = -1;
double currentLargestRandom = -1;
// primariesOfRegionsPerGroup is a sorted array. Since it contains the primary region
// ids for the regions hosted in server, a consecutive repetition means that replicas
// are co-hosted
for (int j = 0; j <= primariesOfRegionsPerGroup.length; j++) {
int primary = j < primariesOfRegionsPerGroup.length
? primariesOfRegionsPerGroup[j] : -1;
if (primary != currentPrimary) { // check for whether we see a new primary
int numReplicas = j - currentPrimaryIndex;
if (numReplicas > 1) { // means consecutive primaries, indicating co-location
// decide to select this primary region id or not
double currentRandom = RANDOM.nextDouble();
// we don't know how many region replicas are co-hosted, we will randomly select one
// using reservoir sampling (http://gregable.com/2007/10/reservoir-sampling.html)
if (currentRandom > currentLargestRandom) {
selectedPrimaryIndex = currentPrimary;
currentLargestRandom = currentRandom;
}
}
currentPrimary = primary;
currentPrimaryIndex = j;
}
}
// we have found the primary id for the region to move. Now find the actual regionIndex
// with the given primary, prefer to move the secondary region.
for (int j = 0; j < regionsPerGroup.length; j++) {
int regionIndex = regionsPerGroup[j];
if (selectedPrimaryIndex == regionIndexToPrimaryIndex[regionIndex]) {
// always move the secondary, not the primary
if (selectedPrimaryIndex != regionIndex) {
return regionIndex;
}
}
}
return -1;
}
@Override
Cluster.Action generate(Cluster cluster) {
int serverIndex = pickRandomServer(cluster);
if (cluster.numServers <= 1 || serverIndex == -1) {
return Cluster.NullAction;
}
int regionIndex = selectCoHostedRegionPerGroup(
cluster.primariesOfRegionsPerServer[serverIndex],
cluster.regionsPerServer[serverIndex],
cluster.regionIndexToPrimaryIndex);
// if there are no pairs of region replicas co-hosted, default to random generator
if (regionIndex == -1) {
// default to randompicker
return randomGenerator.generate(cluster);
}
int toServerIndex = pickOtherRandomServer(cluster, serverIndex);
int toRegionIndex = pickRandomRegion(cluster, toServerIndex, 0.9f);
return getAction(serverIndex, regionIndex, toServerIndex, toRegionIndex);
}
}
/**
* Generates candidates which moves the replicas out of the rack for
* co-hosted region replicas in the same rack
*/
static class RegionReplicaRackCandidateGenerator extends RegionReplicaCandidateGenerator {
@Override
Cluster.Action generate(Cluster cluster) {
int rackIndex = pickRandomRack(cluster);
if (cluster.numRacks <= 1 || rackIndex == -1) {
return super.generate(cluster);
}
int regionIndex = selectCoHostedRegionPerGroup(
cluster.primariesOfRegionsPerRack[rackIndex],
cluster.regionsPerRack[rackIndex],
cluster.regionIndexToPrimaryIndex);
// if there are no pairs of region replicas co-hosted, default to random generator
if (regionIndex == -1) {
// default to randompicker
return randomGenerator.generate(cluster);
}
int serverIndex = cluster.regionIndexToServerIndex[regionIndex];
int toRackIndex = pickOtherRandomRack(cluster, rackIndex);
int rand = RANDOM.nextInt(cluster.serversPerRack[toRackIndex].length);
int toServerIndex = cluster.serversPerRack[toRackIndex][rand];
int toRegionIndex = pickRandomRegion(cluster, toServerIndex, 0.9f);
return getAction(serverIndex, regionIndex, toServerIndex, toRegionIndex);
}
}
/**
* Base class of StochasticLoadBalancer's Cost Functions.
*/
abstract static class CostFunction {
private float multiplier = 0;
protected Cluster cluster;
CostFunction(Configuration c) {
}
boolean isNeeded() {
return true;
}
float getMultiplier() {
return multiplier;
}
void setMultiplier(float m) {
this.multiplier = m;
}
/** Called once per LB invocation to give the cost function
* to initialize it's state, and perform any costly calculation.
*/
void init(Cluster cluster) {
this.cluster = cluster;
}
/** Called once per cluster Action to give the cost function
* an opportunity to update it's state. postAction() is always
* called at least once before cost() is called with the cluster
* that this action is performed on. */
void postAction(Action action) {
switch (action.type) {
case NULL: break;
case ASSIGN_REGION:
AssignRegionAction ar = (AssignRegionAction) action;
regionMoved(ar.region, -1, ar.server);
break;
case MOVE_REGION:
MoveRegionAction mra = (MoveRegionAction) action;
regionMoved(mra.region, mra.fromServer, mra.toServer);
break;
case SWAP_REGIONS:
SwapRegionsAction a = (SwapRegionsAction) action;
regionMoved(a.fromRegion, a.fromServer, a.toServer);
regionMoved(a.toRegion, a.toServer, a.fromServer);
break;
default:
throw new RuntimeException("Uknown action:" + action.type);
}
}
protected void regionMoved(int region, int oldServer, int newServer) {
}
abstract double cost();
/**
* Function to compute a scaled cost using {@link org.apache.commons.math3.stat.descriptive.DescriptiveStatistics}.
* It assumes that this is a zero sum set of costs. It assumes that the worst case
* possible is all of the elements in one region server and the rest having 0.
*
* @param stats the costs
* @return a scaled set of costs.
*/
protected double costFromArray(double[] stats) {
double totalCost = 0;
double total = getSum(stats);
double count = stats.length;
double mean = total/count;
// Compute max as if all region servers had 0 and one had the sum of all costs. This must be
// a zero sum cost for this to make sense.
double max = ((count - 1) * mean) + (total - mean);
// It's possible that there aren't enough regions to go around
double min;
if (count > total) {
min = ((count - total) * mean) + ((1 - mean) * total);
} else {
// Some will have 1 more than everything else.
int numHigh = (int) (total - (Math.floor(mean) * count));
int numLow = (int) (count - numHigh);
min = (numHigh * (Math.ceil(mean) - mean)) + (numLow * (mean - Math.floor(mean)));
}
min = Math.max(0, min);
for (int i=0; i maxMoves) {
return 1000000; // return a number much greater than any of the other cost
}
return scale(0, Math.min(cluster.numRegions, maxMoves), moveCost);
}
}
/**
* Compute the cost of a potential cluster state from skew in number of
* regions on a cluster.
*/
static class RegionCountSkewCostFunction extends CostFunction {
private static final String REGION_COUNT_SKEW_COST_KEY =
"hbase.master.balancer.stochastic.regionCountCost";
private static final float DEFAULT_REGION_COUNT_SKEW_COST = 500;
private double[] stats = null;
RegionCountSkewCostFunction(Configuration conf) {
super(conf);
// Load multiplier should be the greatest as it is the most general way to balance data.
this.setMultiplier(conf.getFloat(REGION_COUNT_SKEW_COST_KEY, DEFAULT_REGION_COUNT_SKEW_COST));
}
@Override
void init(Cluster cluster) {
super.init(cluster);
LOG.debug("{} sees a total of {} servers and {} regions.", getClass().getSimpleName(),
cluster.numServers, cluster.numRegions);
if (LOG.isTraceEnabled()) {
for (int i =0; i < cluster.numServers; i++) {
LOG.trace("{} sees server '{}' has {} regions", getClass().getSimpleName(),
cluster.servers[i], cluster.regionsPerServer[i].length);
}
}
}
@Override
double cost() {
if (stats == null || stats.length != cluster.numServers) {
stats = new double[cluster.numServers];
}
for (int i =0; i < cluster.numServers; i++) {
stats[i] = cluster.regionsPerServer[i].length;
}
return costFromArray(stats);
}
}
/**
* Compute the cost of a potential cluster state from skew in number of
* primary regions on a cluster.
*/
static class PrimaryRegionCountSkewCostFunction extends CostFunction {
private static final String PRIMARY_REGION_COUNT_SKEW_COST_KEY =
"hbase.master.balancer.stochastic.primaryRegionCountCost";
private static final float DEFAULT_PRIMARY_REGION_COUNT_SKEW_COST = 500;
private double[] stats = null;
PrimaryRegionCountSkewCostFunction(Configuration conf) {
super(conf);
// Load multiplier should be the greatest as primary regions serve majority of reads/writes.
this.setMultiplier(conf.getFloat(PRIMARY_REGION_COUNT_SKEW_COST_KEY,
DEFAULT_PRIMARY_REGION_COUNT_SKEW_COST));
}
@Override
boolean isNeeded() {
return cluster.hasRegionReplicas;
}
@Override
double cost() {
if (!cluster.hasRegionReplicas) {
return 0;
}
if (stats == null || stats.length != cluster.numServers) {
stats = new double[cluster.numServers];
}
for (int i = 0; i < cluster.numServers; i++) {
stats[i] = 0;
for (int regionIdx : cluster.regionsPerServer[i]) {
if (regionIdx == cluster.regionIndexToPrimaryIndex[regionIdx]) {
stats[i]++;
}
}
}
return costFromArray(stats);
}
}
/**
* Compute the cost of a potential cluster configuration based upon how evenly
* distributed tables are.
*/
static class TableSkewCostFunction extends CostFunction {
private static final String TABLE_SKEW_COST_KEY =
"hbase.master.balancer.stochastic.tableSkewCost";
private static final float DEFAULT_TABLE_SKEW_COST = 35;
TableSkewCostFunction(Configuration conf) {
super(conf);
this.setMultiplier(conf.getFloat(TABLE_SKEW_COST_KEY, DEFAULT_TABLE_SKEW_COST));
}
@Override
double cost() {
double max = cluster.numRegions;
double min = ((double) cluster.numRegions) / cluster.numServers;
double value = 0;
for (int i = 0; i < cluster.numMaxRegionsPerTable.length; i++) {
value += cluster.numMaxRegionsPerTable[i];
}
return scale(min, max, value);
}
}
/**
* Compute a cost of a potential cluster configuration based upon where
* {@link org.apache.hadoop.hbase.regionserver.HStoreFile}s are located.
*/
static abstract class LocalityBasedCostFunction extends CostFunction {
private final LocalityType type;
private double bestLocality; // best case locality across cluster weighted by local data size
private double locality; // current locality across cluster weighted by local data size
private MasterServices services;
LocalityBasedCostFunction(Configuration conf,
MasterServices srv,
LocalityType type,
String localityCostKey,
float defaultLocalityCost) {
super(conf);
this.type = type;
this.setMultiplier(conf.getFloat(localityCostKey, defaultLocalityCost));
this.services = srv;
this.locality = 0.0;
this.bestLocality = 0.0;
}
/**
* Maps region to the current entity (server or rack) on which it is stored
*/
abstract int regionIndexToEntityIndex(int region);
public void setServices(MasterServices srvc) {
this.services = srvc;
}
@Override
void init(Cluster cluster) {
super.init(cluster);
locality = 0.0;
bestLocality = 0.0;
// If no master, no computation will work, so assume 0 cost
if (this.services == null) {
return;
}
for (int region = 0; region < cluster.numRegions; region++) {
locality += getWeightedLocality(region, regionIndexToEntityIndex(region));
bestLocality += getWeightedLocality(region, getMostLocalEntityForRegion(region));
}
// We normalize locality to be a score between 0 and 1.0 representing how good it
// is compared to how good it could be. If bestLocality is 0, assume locality is 100
// (and the cost is 0)
locality = bestLocality == 0 ? 1.0 : locality / bestLocality;
}
@Override
protected void regionMoved(int region, int oldServer, int newServer) {
int oldEntity = type == LocalityType.SERVER ? oldServer : cluster.serverIndexToRackIndex[oldServer];
int newEntity = type == LocalityType.SERVER ? newServer : cluster.serverIndexToRackIndex[newServer];
if (this.services == null) {
return;
}
double localityDelta = getWeightedLocality(region, newEntity) - getWeightedLocality(region, oldEntity);
double normalizedDelta = bestLocality == 0 ? 0.0 : localityDelta / bestLocality;
locality += normalizedDelta;
}
@Override
double cost() {
return 1 - locality;
}
private int getMostLocalEntityForRegion(int region) {
return cluster.getOrComputeRegionsToMostLocalEntities(type)[region];
}
private double getWeightedLocality(int region, int entity) {
return cluster.getOrComputeWeightedLocality(region, entity, type);
}
}
static class ServerLocalityCostFunction extends LocalityBasedCostFunction {
private static final String LOCALITY_COST_KEY = "hbase.master.balancer.stochastic.localityCost";
private static final float DEFAULT_LOCALITY_COST = 25;
ServerLocalityCostFunction(Configuration conf, MasterServices srv) {
super(
conf,
srv,
LocalityType.SERVER,
LOCALITY_COST_KEY,
DEFAULT_LOCALITY_COST
);
}
@Override
int regionIndexToEntityIndex(int region) {
return cluster.regionIndexToServerIndex[region];
}
}
static class RackLocalityCostFunction extends LocalityBasedCostFunction {
private static final String RACK_LOCALITY_COST_KEY = "hbase.master.balancer.stochastic.rackLocalityCost";
private static final float DEFAULT_RACK_LOCALITY_COST = 15;
public RackLocalityCostFunction(Configuration conf, MasterServices services) {
super(
conf,
services,
LocalityType.RACK,
RACK_LOCALITY_COST_KEY,
DEFAULT_RACK_LOCALITY_COST
);
}
@Override
int regionIndexToEntityIndex(int region) {
return cluster.getRackForRegion(region);
}
}
/**
* Base class the allows writing costs functions from rolling average of some
* number from RegionLoad.
*/
abstract static class CostFromRegionLoadFunction extends CostFunction {
private ClusterMetrics clusterStatus = null;
private Map> loads = null;
private double[] stats = null;
CostFromRegionLoadFunction(Configuration conf) {
super(conf);
}
void setClusterMetrics(ClusterMetrics status) {
this.clusterStatus = status;
}
void setLoads(Map> l) {
this.loads = l;
}
@Override
double cost() {
if (clusterStatus == null || loads == null) {
return 0;
}
if (stats == null || stats.length != cluster.numServers) {
stats = new double[cluster.numServers];
}
for (int i =0; i < stats.length; i++) {
//Cost this server has from RegionLoad
long cost = 0;
// for every region on this server get the rl
for(int regionIndex:cluster.regionsPerServer[i]) {
Collection regionLoadList = cluster.regionLoads[regionIndex];
// Now if we found a region load get the type of cost that was requested.
if (regionLoadList != null) {
cost = (long) (cost + getRegionLoadCost(regionLoadList));
}
}
// Add the total cost to the stats.
stats[i] = cost;
}
// Now return the scaled cost from data held in the stats object.
return costFromArray(stats);
}
protected double getRegionLoadCost(Collection regionLoadList) {
double cost = 0;
for (BalancerRegionLoad rl : regionLoadList) {
cost += getCostFromRl(rl);
}
return cost / regionLoadList.size();
}
protected abstract double getCostFromRl(BalancerRegionLoad rl);
}
/**
* Class to be used for the subset of RegionLoad costs that should be treated as rates.
* We do not compare about the actual rate in requests per second but rather the rate relative
* to the rest of the regions.
*/
abstract static class CostFromRegionLoadAsRateFunction extends CostFromRegionLoadFunction {
CostFromRegionLoadAsRateFunction(Configuration conf) {
super(conf);
}
@Override
protected double getRegionLoadCost(Collection regionLoadList) {
double cost = 0;
double previous = 0;
boolean isFirst = true;
for (BalancerRegionLoad rl : regionLoadList) {
double current = getCostFromRl(rl);
if (isFirst) {
isFirst = false;
} else {
cost += current - previous;
}
previous = current;
}
return Math.max(0, cost / (regionLoadList.size() - 1));
}
}
/**
* Compute the cost of total number of read requests The more unbalanced the higher the
* computed cost will be. This uses a rolling average of regionload.
*/
static class ReadRequestCostFunction extends CostFromRegionLoadAsRateFunction {
private static final String READ_REQUEST_COST_KEY =
"hbase.master.balancer.stochastic.readRequestCost";
private static final float DEFAULT_READ_REQUEST_COST = 5;
ReadRequestCostFunction(Configuration conf) {
super(conf);
this.setMultiplier(conf.getFloat(READ_REQUEST_COST_KEY, DEFAULT_READ_REQUEST_COST));
}
@Override
protected double getCostFromRl(BalancerRegionLoad rl) {
return rl.getReadRequestsCount();
}
}
/**
* Compute the cost of total number of write requests. The more unbalanced the higher the
* computed cost will be. This uses a rolling average of regionload.
*/
static class WriteRequestCostFunction extends CostFromRegionLoadAsRateFunction {
private static final String WRITE_REQUEST_COST_KEY =
"hbase.master.balancer.stochastic.writeRequestCost";
private static final float DEFAULT_WRITE_REQUEST_COST = 5;
WriteRequestCostFunction(Configuration conf) {
super(conf);
this.setMultiplier(conf.getFloat(WRITE_REQUEST_COST_KEY, DEFAULT_WRITE_REQUEST_COST));
}
@Override
protected double getCostFromRl(BalancerRegionLoad rl) {
return rl.getWriteRequestsCount();
}
}
/**
* A cost function for region replicas. We give a very high cost to hosting
* replicas of the same region in the same host. We do not prevent the case
* though, since if numReplicas > numRegionServers, we still want to keep the
* replica open.
*/
static class RegionReplicaHostCostFunction extends CostFunction {
private static final String REGION_REPLICA_HOST_COST_KEY =
"hbase.master.balancer.stochastic.regionReplicaHostCostKey";
private static final float DEFAULT_REGION_REPLICA_HOST_COST_KEY = 100000;
long maxCost = 0;
long[] costsPerGroup; // group is either server, host or rack
int[][] primariesOfRegionsPerGroup;
public RegionReplicaHostCostFunction(Configuration conf) {
super(conf);
this.setMultiplier(conf.getFloat(REGION_REPLICA_HOST_COST_KEY,
DEFAULT_REGION_REPLICA_HOST_COST_KEY));
}
@Override
void init(Cluster cluster) {
super.init(cluster);
// max cost is the case where every region replica is hosted together regardless of host
maxCost = cluster.numHosts > 1 ? getMaxCost(cluster) : 0;
costsPerGroup = new long[cluster.numHosts];
primariesOfRegionsPerGroup = cluster.multiServersPerHost // either server based or host based
? cluster.primariesOfRegionsPerHost
: cluster.primariesOfRegionsPerServer;
for (int i = 0 ; i < primariesOfRegionsPerGroup.length; i++) {
costsPerGroup[i] = costPerGroup(primariesOfRegionsPerGroup[i]);
}
}
long getMaxCost(Cluster cluster) {
if (!cluster.hasRegionReplicas) {
return 0; // short circuit
}
// max cost is the case where every region replica is hosted together regardless of host
int[] primariesOfRegions = new int[cluster.numRegions];
System.arraycopy(cluster.regionIndexToPrimaryIndex, 0, primariesOfRegions, 0,
cluster.regions.length);
Arrays.sort(primariesOfRegions);
// compute numReplicas from the sorted array
return costPerGroup(primariesOfRegions);
}
@Override
boolean isNeeded() {
return cluster.hasRegionReplicas;
}
@Override
double cost() {
if (maxCost <= 0) {
return 0;
}
long totalCost = 0;
for (int i = 0 ; i < costsPerGroup.length; i++) {
totalCost += costsPerGroup[i];
}
return scale(0, maxCost, totalCost);
}
/**
* For each primary region, it computes the total number of replicas in the array (numReplicas)
* and returns a sum of numReplicas-1 squared. For example, if the server hosts
* regions a, b, c, d, e, f where a and b are same replicas, and c,d,e are same replicas, it
* returns (2-1) * (2-1) + (3-1) * (3-1) + (1-1) * (1-1).
* @param primariesOfRegions a sorted array of primary regions ids for the regions hosted
* @return a sum of numReplicas-1 squared for each primary region in the group.
*/
protected long costPerGroup(int[] primariesOfRegions) {
long cost = 0;
int currentPrimary = -1;
int currentPrimaryIndex = -1;
// primariesOfRegions is a sorted array of primary ids of regions. Replicas of regions
// sharing the same primary will have consecutive numbers in the array.
for (int j = 0 ; j <= primariesOfRegions.length; j++) {
int primary = j < primariesOfRegions.length ? primariesOfRegions[j] : -1;
if (primary != currentPrimary) { // we see a new primary
int numReplicas = j - currentPrimaryIndex;
// square the cost
if (numReplicas > 1) { // means consecutive primaries, indicating co-location
cost += (numReplicas - 1) * (numReplicas - 1);
}
currentPrimary = primary;
currentPrimaryIndex = j;
}
}
return cost;
}
@Override
protected void regionMoved(int region, int oldServer, int newServer) {
if (maxCost <= 0) {
return; // no need to compute
}
if (cluster.multiServersPerHost) {
int oldHost = cluster.serverIndexToHostIndex[oldServer];
int newHost = cluster.serverIndexToHostIndex[newServer];
if (newHost != oldHost) {
costsPerGroup[oldHost] = costPerGroup(cluster.primariesOfRegionsPerHost[oldHost]);
costsPerGroup[newHost] = costPerGroup(cluster.primariesOfRegionsPerHost[newHost]);
}
} else {
costsPerGroup[oldServer] = costPerGroup(cluster.primariesOfRegionsPerServer[oldServer]);
costsPerGroup[newServer] = costPerGroup(cluster.primariesOfRegionsPerServer[newServer]);
}
}
}
/**
* A cost function for region replicas for the rack distribution. We give a relatively high
* cost to hosting replicas of the same region in the same rack. We do not prevent the case
* though.
*/
static class RegionReplicaRackCostFunction extends RegionReplicaHostCostFunction {
private static final String REGION_REPLICA_RACK_COST_KEY =
"hbase.master.balancer.stochastic.regionReplicaRackCostKey";
private static final float DEFAULT_REGION_REPLICA_RACK_COST_KEY = 10000;
public RegionReplicaRackCostFunction(Configuration conf) {
super(conf);
this.setMultiplier(conf.getFloat(REGION_REPLICA_RACK_COST_KEY,
DEFAULT_REGION_REPLICA_RACK_COST_KEY));
}
@Override
void init(Cluster cluster) {
this.cluster = cluster;
if (cluster.numRacks <= 1) {
maxCost = 0;
return; // disabled for 1 rack
}
// max cost is the case where every region replica is hosted together regardless of rack
maxCost = getMaxCost(cluster);
costsPerGroup = new long[cluster.numRacks];
for (int i = 0 ; i < cluster.primariesOfRegionsPerRack.length; i++) {
costsPerGroup[i] = costPerGroup(cluster.primariesOfRegionsPerRack[i]);
}
}
@Override
protected void regionMoved(int region, int oldServer, int newServer) {
if (maxCost <= 0) {
return; // no need to compute
}
int oldRack = cluster.serverIndexToRackIndex[oldServer];
int newRack = cluster.serverIndexToRackIndex[newServer];
if (newRack != oldRack) {
costsPerGroup[oldRack] = costPerGroup(cluster.primariesOfRegionsPerRack[oldRack]);
costsPerGroup[newRack] = costPerGroup(cluster.primariesOfRegionsPerRack[newRack]);
}
}
}
/**
* Compute the cost of total memstore size. The more unbalanced the higher the
* computed cost will be. This uses a rolling average of regionload.
*/
static class MemStoreSizeCostFunction extends CostFromRegionLoadAsRateFunction {
private static final String MEMSTORE_SIZE_COST_KEY =
"hbase.master.balancer.stochastic.memstoreSizeCost";
private static final float DEFAULT_MEMSTORE_SIZE_COST = 5;
MemStoreSizeCostFunction(Configuration conf) {
super(conf);
this.setMultiplier(conf.getFloat(MEMSTORE_SIZE_COST_KEY, DEFAULT_MEMSTORE_SIZE_COST));
}
@Override
protected double getCostFromRl(BalancerRegionLoad rl) {
return rl.getMemStoreSizeMB();
}
}
/**
* Compute the cost of total open storefiles size. The more unbalanced the higher the
* computed cost will be. This uses a rolling average of regionload.
*/
static class StoreFileCostFunction extends CostFromRegionLoadFunction {
private static final String STOREFILE_SIZE_COST_KEY =
"hbase.master.balancer.stochastic.storefileSizeCost";
private static final float DEFAULT_STOREFILE_SIZE_COST = 5;
StoreFileCostFunction(Configuration conf) {
super(conf);
this.setMultiplier(conf.getFloat(STOREFILE_SIZE_COST_KEY, DEFAULT_STOREFILE_SIZE_COST));
}
@Override
protected double getCostFromRl(BalancerRegionLoad rl) {
return rl.getStorefileSizeMB();
}
}
/**
* A helper function to compose the attribute name from tablename and costfunction name
*/
public static String composeAttributeName(String tableName, String costFunctionName) {
return tableName + TABLE_FUNCTION_SEP + costFunctionName;
}
}