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HBASE-25739 TableSkewCostFunction need to use aggregated deviation (#3067) 

Signed-off-by: Michael Stack <stack@apache.org>
Reviewed-by: David Manning <david.manning@salesforce.com>
This commit is contained in:
clarax 2021-04-15 13:12:07 -07:00 committed by GitHub
parent 6cf4fdde61
commit 533c84d330
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3 changed files with 131 additions and 94 deletions
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120
hbase-server/src/main/java/org/apache/hadoop/hbase/master/balancer/BaseLoadBalancer.java
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@ -162,7 +162,12 @@ public abstract class BaseLoadBalancer implements LoadBalancer {
int[] initialRegionIndexToServerIndex; //regionIndex -> serverIndex (initial cluster state)
int[] regionIndexToTableIndex; //regionIndex -> tableIndex
int[][] numRegionsPerServerPerTable; //serverIndex -> tableIndex -> # regions
int[] numMaxRegionsPerTable; //tableIndex -> max number of regions in a single RS
int[] numRegionsPerTable; // tableIndex -> region count
double[] meanRegionsPerTable; // mean region count per table
double regionSkewByTable; // skew on RS per by table
double minRegionSkewByTable; // min skew on RS per by table
double maxRegionSkewByTable; // max skew on RS per by table
int[] regionIndexToPrimaryIndex; //regionIndex -> regionIndex of the primary
boolean hasRegionReplicas = false; //whether there is regions with replicas
@ -370,6 +375,7 @@ public abstract class BaseLoadBalancer implements LoadBalancer {
numTables = tables.size();
numRegionsPerServerPerTable = new int[numServers][numTables];
numRegionsPerTable = new int[numTables];
for (int i = 0; i < numServers; i++) {
for (int j = 0; j < numTables; j++) {
@ -377,21 +383,29 @@ public abstract class BaseLoadBalancer implements LoadBalancer {
}
}
for (int i = 0; i < numTables; i++) {
numRegionsPerTable[i] = 0;
}
for (int i=0; i < regionIndexToServerIndex.length; i++) {
if (regionIndexToServerIndex[i] >= 0) {
numRegionsPerServerPerTable[regionIndexToServerIndex[i]][regionIndexToTableIndex[i]]++;
numRegionsPerTable[regionIndexToTableIndex[i]]++;
}
}
numMaxRegionsPerTable = new int[numTables];
for (int[] aNumRegionsPerServerPerTable : numRegionsPerServerPerTable) {
for (tableIndex = 0; tableIndex < aNumRegionsPerServerPerTable.length; tableIndex++) {
if (aNumRegionsPerServerPerTable[tableIndex] > numMaxRegionsPerTable[tableIndex]) {
numMaxRegionsPerTable[tableIndex] = aNumRegionsPerServerPerTable[tableIndex];
}
}
// Avoid repeated computation for planning
meanRegionsPerTable = new double[numTables];
maxRegionSkewByTable = 0;
minRegionSkewByTable = 0;
for (int i = 0; i < numTables; i++) {
meanRegionsPerTable[i] = Double.valueOf(numRegionsPerTable[i]) / numServers;
minRegionSkewByTable += Cluster.getMinSkew(numRegionsPerTable[i], numServers);
maxRegionSkewByTable += Cluster.getMaxSkew(numRegionsPerTable[i], numServers);
}
computeRegionSkewPerTable();
for (int i = 0; i < regions.length; i ++) {
RegionInfo info = regions[i];
if (RegionReplicaUtil.isDefaultReplica(info)) {
@ -516,6 +530,53 @@ public abstract class BaseLoadBalancer implements LoadBalancer {
return numRegions < minLoad;
}
/**
* Return the min skew of distribution
*/
public static double getMinSkew(double total, double numServers) {
double mean = total / numServers;
// It's possible that there aren't enough regions to go around
double min;
if (numServers > total) {
min = ((numServers - total) * mean + (1 - mean) * total) ;
} else {
// Some will have 1 more than everything else.
int numHigh = (int) (total - (Math.floor(mean) * numServers));
int numLow = (int) (numServers - numHigh);
min = numHigh * (Math.ceil(mean) - mean) + numLow * (mean - Math.floor(mean));
}
return min;
}
/**
* Return the max deviation of distribution
* 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.
*/
public static double getMaxSkew(double total, double numServers) {
double mean = total / numServers;
return (total - mean) + (numServers - 1) * mean;
}
/**
* Scale the value between 0 and 1.
*
* @param min Min value
* @param max The Max value
* @param value The value to be scaled.
* @return The scaled value.
*/
public static double scale(double min, double max, double value) {
if (max <= min || value <= min) {
return 0;
}
if ((max - min) == 0) {
return 0;
}
return Math.max(0d, Math.min(1d, (value - min) / (max - min)));
}
/**
* Retrieves and lazily initializes a field storing the locality of
* every region/server combination
@ -573,6 +634,21 @@ public abstract class BaseLoadBalancer implements LoadBalancer {
return regionLoads[region].getLast().getStorefileSizeMB();
}
/**
* Recompute the region skew during init or plan of moves.
*/
private void computeRegionSkewPerTable() {
// reinitialize for recomputation
regionSkewByTable = 0;
for (int[] aNumRegionsPerServerPerTable : numRegionsPerServerPerTable) {
for (int tableIndex = 0; tableIndex < aNumRegionsPerServerPerTable.length; tableIndex++) {
regionSkewByTable += Math.abs(aNumRegionsPerServerPerTable[tableIndex]
- meanRegionsPerTable[tableIndex]);
}
}
}
/**
* Computes and caches the locality for each region/rack combinations,
* as well as storing a mapping of region -> server and region -> rack such that server
@ -828,22 +904,20 @@ public abstract class BaseLoadBalancer implements LoadBalancer {
int tableIndex = regionIndexToTableIndex[region];
if (oldServer >= 0) {
numRegionsPerServerPerTable[oldServer][tableIndex]--;
// update regionSkewPerTable for the move from old server
regionSkewByTable +=
Math.abs(numRegionsPerServerPerTable[oldServer][tableIndex]
- meanRegionsPerTable[tableIndex])
- Math.abs(numRegionsPerServerPerTable[oldServer][tableIndex] + 1
- meanRegionsPerTable[tableIndex]);
}
numRegionsPerServerPerTable[newServer][tableIndex]++;
//check whether this caused maxRegionsPerTable in the new Server to be updated
if (numRegionsPerServerPerTable[newServer][tableIndex] > numMaxRegionsPerTable[tableIndex]) {
numMaxRegionsPerTable[tableIndex] = numRegionsPerServerPerTable[newServer][tableIndex];
} else if (oldServer >= 0 && (numRegionsPerServerPerTable[oldServer][tableIndex] + 1)
== numMaxRegionsPerTable[tableIndex]) {
//recompute maxRegionsPerTable since the previous value was coming from the old server
numMaxRegionsPerTable[tableIndex] = 0;
for (int[] aNumRegionsPerServerPerTable : numRegionsPerServerPerTable) {
if (aNumRegionsPerServerPerTable[tableIndex] > numMaxRegionsPerTable[tableIndex]) {
numMaxRegionsPerTable[tableIndex] = aNumRegionsPerServerPerTable[tableIndex];
}
}
}
// update regionSkewPerTable for the move to new server
regionSkewByTable +=
Math.abs(numRegionsPerServerPerTable[newServer][tableIndex]
- meanRegionsPerTable[tableIndex])
- Math.abs(numRegionsPerServerPerTable[newServer][tableIndex] - 1
- meanRegionsPerTable[tableIndex]);
// update for servers
int primary = regionIndexToPrimaryIndex[region];
@ -1013,7 +1087,7 @@ public abstract class BaseLoadBalancer implements LoadBalancer {
.append(Arrays.toString(serverIndicesSortedByRegionCount))
.append(", regionsPerServer=").append(Arrays.deepToString(regionsPerServer));
desc.append(", numMaxRegionsPerTable=").append(Arrays.toString(numMaxRegionsPerTable))
desc.append(", regionSkewByTable=").append(regionSkewByTable)
.append(", numRegions=").append(numRegions).append(", numServers=").append(numServers)
.append(", numTables=").append(numTables).append(", numMovedRegions=")
.append(numMovedRegions).append('}');

101
hbase-server/src/main/java/org/apache/hadoop/hbase/master/balancer/StochasticLoadBalancer.java
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@ -762,6 +762,7 @@ public class StochasticLoadBalancer extends BaseLoadBalancer {
boolean isNeeded() {
return true;
}
float getMultiplier() {
return multiplier;
}
@ -770,35 +771,39 @@ public class StochasticLoadBalancer extends BaseLoadBalancer {
this.multiplier = m;
}
/** Called once per LB invocation to give the cost function
/**
* 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
/**
* 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. */
* 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);
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);
}
}
@ -822,59 +827,25 @@ public class StochasticLoadBalancer extends BaseLoadBalancer {
double total = getSum(stats);
double count = stats.length;
double mean = total/count;
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<stats.length; i++) {
for (int i = 0; i < stats.length; i++) {
double n = stats[i];
double diff = Math.abs(mean - n);
totalCost += diff;
}
double scaled = scale(min, max, totalCost);
return scaled;
return Cluster
.scale(Cluster.getMinSkew(total, count), Cluster.getMaxSkew(total, count), totalCost);
}
private double getSum(double[] stats) {
double total = 0;
for(double s:stats) {
for (double s : stats) {
total += s;
}
return total;
}
/**
* Scale the value between 0 and 1.
*
* @param min Min value
* @param max The Max value
* @param value The value to be scaled.
* @return The scaled value.
*/
protected double scale(double min, double max, double value) {
if (max <= min || value <= min) {
return 0;
}
if ((max - min) == 0) return 0;
return Math.max(0d, Math.min(1d, (value - min) / (max - min)));
}
}
/**
@ -927,7 +898,7 @@ public class StochasticLoadBalancer extends BaseLoadBalancer {
return 1000000; // return a number much greater than any of the other cost
}
return scale(0, Math.min(cluster.numRegions, maxMoves), moveCost);
return Cluster.scale(0, Math.min(cluster.numRegions, maxMoves), moveCost);
}
}
@ -1035,15 +1006,7 @@ public class StochasticLoadBalancer extends BaseLoadBalancer {
@Override
protected 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);
return Cluster.scale(cluster.minRegionSkewByTable, cluster.maxRegionSkewByTable, cluster.regionSkewByTable);
}
}
@ -1366,7 +1329,7 @@ public class StochasticLoadBalancer extends BaseLoadBalancer {
for (int i = 0 ; i < costsPerGroup.length; i++) {
totalCost += costsPerGroup[i];
}
return scale(0, maxCost, totalCost);
return Cluster.scale(0, maxCost, totalCost);
}
/**

4
hbase-server/src/test/java/org/apache/hadoop/hbase/master/balancer/TestBaseLoadBalancer.java
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@ -390,8 +390,8 @@ public class TestBaseLoadBalancer extends BalancerTestBase {
// now move region1 from servers[0] to servers[2]
cluster.doAction(new MoveRegionAction(0, 0, 2));
// check that the numMaxRegionsPerTable for "table" has increased to 2
assertEquals(2, cluster.numMaxRegionsPerTable[0]);
// check that the regionSkewByTable for "table" has increased to 2
assertEquals(2, cluster.regionSkewByTable, 0.01);
// now repeat check whether moving region1 from servers[1] to servers[2]
// would lower availability
assertTrue(cluster.wouldLowerAvailability(hri1, servers[2]));