HBASE-14604 Improve MoveCostFunction in StochasticLoadBalancer (Guanghao Zhang)

hbase-server/src/main/java/org/apache/hadoop/hbase/master/balancer/BaseLoadBalancer.java

@@ -52,6 +52,7 @@ import org.apache.hadoop.hbase.master.RegionPlan;
 import org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer.Cluster.Action.Type;
 import org.apache.hadoop.util.StringUtils;
 
+import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Joiner;
 import com.google.common.collect.ArrayListMultimap;
 import com.google.common.collect.Lists;
@@ -896,6 +897,16 @@ public abstract class BaseLoadBalancer implements LoadBalancer {
       }
     }
 
+    @VisibleForTesting
+    protected void setNumRegions(int numRegions) {
+      this.numRegions = numRegions;
+    }
+
+    @VisibleForTesting
+    protected void setNumMovedRegions(int numMovedRegions) {
+      this.numMovedRegions = numMovedRegions;
+    }
+
     @edu.umd.cs.findbugs.annotations.SuppressWarnings(value="SBSC_USE_STRINGBUFFER_CONCATENATION",
         justification="Not important but should be fixed")
     @Override

hbase-server/src/main/java/org/apache/hadoop/hbase/master/balancer/StochasticLoadBalancer.java

@@ -1026,7 +1026,7 @@ public class StochasticLoadBalancer extends BaseLoadBalancer {
         return 1000000;   // return a number much greater than any of the other cost
       }
 
-      return scale(0, cluster.numRegions, moveCost);
+      return scale(0, Math.min(cluster.numRegions, maxMoves), moveCost);
     }
   }
 

hbase-server/src/test/java/org/apache/hadoop/hbase/master/balancer/TestStochasticLoadBalancer.java

@@ -120,6 +120,44 @@ public class TestStochasticLoadBalancer extends BalancerTestBase {
 
   }
 
+  @Test
+  public void testMoveCost() throws Exception {
+    Configuration conf = HBaseConfiguration.create();
+    StochasticLoadBalancer.CostFunction
+        costFunction = new StochasticLoadBalancer.MoveCostFunction(conf);
+    for (int[] mockCluster : clusterStateMocks) {
+      BaseLoadBalancer.Cluster cluster = mockCluster(mockCluster);
+      costFunction.init(cluster);
+      double cost = costFunction.cost();
+      assertEquals(0.0f, cost, 0.001);
+
+      // cluster region number is smaller than maxMoves=600
+      cluster.setNumRegions(200);
+      cluster.setNumMovedRegions(10);
+      cost = costFunction.cost();
+      assertEquals(0.05f, cost, 0.001);
+      cluster.setNumMovedRegions(100);
+      cost = costFunction.cost();
+      assertEquals(0.5f, cost, 0.001);
+      cluster.setNumMovedRegions(200);
+      cost = costFunction.cost();
+      assertEquals(1.0f, cost, 0.001);
+
+
+      // cluster region number is bigger than maxMoves=2500
+      cluster.setNumRegions(10000);
+      cluster.setNumMovedRegions(250);
+      cost = costFunction.cost();
+      assertEquals(0.1f, cost, 0.001);
+      cluster.setNumMovedRegions(1250);
+      cost = costFunction.cost();
+      assertEquals(0.5f, cost, 0.001);
+      cluster.setNumMovedRegions(2500);
+      cost = costFunction.cost();
+      assertEquals(1.0f, cost, 0.01);
+    }
+  }
+
   @Test
   public void testSkewCost() {
     Configuration conf = HBaseConfiguration.create();