minor changes from review

server/src/main/java/io/druid/server/coordinator/AbstractCostBalancerStrategy.java

@@ -33,11 +33,11 @@ public abstract class AbstractCostBalancerStrategy implements BalancerStrategy
   private static final int DAY_IN_MILLIS = 1000 * 60 * 60 * 24;
   private static final int SEVEN_DAYS_IN_MILLIS = 7 * DAY_IN_MILLIS;
   private static final int THIRTY_DAYS_IN_MILLIS = 30 * DAY_IN_MILLIS;
-  private final long referenceTimestampInMillis;
+  private final long referenceTimestamp;
 
   public AbstractCostBalancerStrategy(DateTime referenceTimestamp)
   {
-    this.referenceTimestampInMillis = referenceTimestamp.getMillis();
+    this.referenceTimestamp = referenceTimestamp.getMillis();
   }
 
   @Override
@@ -103,8 +103,8 @@ public abstract class AbstractCostBalancerStrategy implements BalancerStrategy
       dataSourcePenalty = 2;
     }
 
-    double segment1diff = referenceTimestampInMillis - segment1.getInterval().getEndMillis();
-    double segment2diff = referenceTimestampInMillis - segment2.getInterval().getEndMillis();
+    double segment1diff = referenceTimestamp - segment1.getInterval().getEndMillis();
+    double segment2diff = referenceTimestamp - segment2.getInterval().getEndMillis();
     if (segment1diff < SEVEN_DAYS_IN_MILLIS && segment2diff < SEVEN_DAYS_IN_MILLIS) {
       recencyPenalty = (2 - segment1diff / SEVEN_DAYS_IN_MILLIS) * (2 - segment2diff / SEVEN_DAYS_IN_MILLIS);
     }

server/src/main/java/io/druid/server/coordinator/BalancerStrategy.java

@@ -25,12 +25,6 @@ import java.util.List;
 
 public interface BalancerStrategy
 {
-  public static final String COST = "cost";
-
-  public static final String COST_MULTI = "cost_multi";
-
-  public static final String RANDOM = "random";
-
   public ServerHolder findNewSegmentHomeBalancer(final DataSegment proposalSegment, final List<ServerHolder> serverHolders);
 
   public ServerHolder findNewSegmentHomeReplicator(final DataSegment proposalSegment, final List<ServerHolder> serverHolders);

server/src/main/java/io/druid/server/coordinator/CoordinatorDynamicConfig.java

@@ -31,7 +31,7 @@ public class CoordinatorDynamicConfig
   private final int maxSegmentsToMove;
   private final int replicantLifetime;
   private final int replicationThrottleLimit;
-  private final int costBalancerThreads;
+  private final int balancerComputeThreads;
   private final boolean emitBalancingStats;
 
   @JsonCreator
@@ -42,7 +42,7 @@ public class CoordinatorDynamicConfig
       @JsonProperty("maxSegmentsToMove") int maxSegmentsToMove,
       @JsonProperty("replicantLifetime") int replicantLifetime,
       @JsonProperty("replicationThrottleLimit") int replicationThrottleLimit,
-      @JsonProperty("costBalancerThreads") int costBalancerThreads,
+      @JsonProperty("balancerComputeThreads") int balancerComputeThreads,
       @JsonProperty("emitBalancingStats") boolean emitBalancingStats
   )
   {
@@ -53,7 +53,7 @@ public class CoordinatorDynamicConfig
     this.replicantLifetime = replicantLifetime;
     this.replicationThrottleLimit = replicationThrottleLimit;
     this.emitBalancingStats = emitBalancingStats;
-    this.costBalancerThreads = costBalancerThreads;
+    this.balancerComputeThreads = balancerComputeThreads;
   }
 
   @JsonProperty
@@ -99,9 +99,9 @@ public class CoordinatorDynamicConfig
   }
 
   @JsonProperty
-  public int getCostBalancerThreads()
+  public int getBalancerComputeThreads()
   {
-    return costBalancerThreads;
+    return balancerComputeThreads;
   }
 
   public static class Builder
@@ -113,7 +113,7 @@ public class CoordinatorDynamicConfig
     private int replicantLifetime;
     private int replicationThrottleLimit;
     private boolean emitBalancingStats;
-    private int costBalancerThreads;
+    private int balancerComputeThreads;
 
     public Builder()
     {
@@ -127,7 +127,7 @@ public class CoordinatorDynamicConfig
         int maxSegmentsToMove,
         int replicantLifetime,
         int replicationThrottleLimit,
-        int costBalancerThreads,
+        int balancerComputeThreads,
         boolean emitBalancingStats
     )
     {
@@ -138,7 +138,7 @@ public class CoordinatorDynamicConfig
       this.replicantLifetime = replicantLifetime;
       this.replicationThrottleLimit = replicationThrottleLimit;
       this.emitBalancingStats = emitBalancingStats;
-      this.costBalancerThreads = costBalancerThreads;
+      this.balancerComputeThreads = balancerComputeThreads;
     }
 
     public Builder withMillisToWaitBeforeDeleting(long millisToWaitBeforeDeleting)
@@ -177,9 +177,9 @@ public class CoordinatorDynamicConfig
       return this;
     }
 
-    public Builder withCostBalancerThreads(int costBalancerThreads)
+    public Builder withBalancerComputeThreads(int balancerComputeThreads)
     {
-      this.costBalancerThreads = costBalancerThreads;
+      this.balancerComputeThreads = balancerComputeThreads;
       return this;
     }
 
@@ -192,7 +192,7 @@ public class CoordinatorDynamicConfig
           maxSegmentsToMove,
           replicantLifetime,
           replicationThrottleLimit,
-          costBalancerThreads,
+          balancerComputeThreads,
           emitBalancingStats
       );
     }

server/src/main/java/io/druid/server/coordinator/DruidCoordinator.java

@@ -19,9 +19,6 @@
 
 package io.druid.server.coordinator;
 
-import static io.druid.server.coordinator.BalancerStrategy.COST;
-import static io.druid.server.coordinator.BalancerStrategy.COST_MULTI;
-import static io.druid.server.coordinator.BalancerStrategy.RANDOM;
 import com.google.common.base.Function;
 import com.google.common.base.Predicate;
 import com.google.common.base.Throwables;
@@ -740,7 +737,7 @@ public class DruidCoordinator
         }
 
         BalancerStrategyFactory factory =
-            new CostBalancerMultithreadStrategyFactory(getDynamicConfigs().getCostBalancerThreads());
+            new CostBalancerMultithreadStrategyFactory(getDynamicConfigs().getBalancerComputeThreads());
 
         // Do coordinator stuff.
         DruidCoordinatorRuntimeParams params =

server/src/main/java/io/druid/server/coordinator/DruidCoordinatorConfig.java

@@ -42,10 +42,6 @@ public abstract class DruidCoordinatorConfig
   @Default("PT1800s")
   public abstract Duration getCoordinatorIndexingPeriod();
 
-  @Config("druid.coordinator.balancer.strategy")
-  @Default("cost")
-  public abstract String getCoordinatorBalancerStrategy();
-
   @Config("druid.coordinator.merge.on")
   public boolean isMergeSegments()
   {