clarax commented on a change in pull request #3356:
URL: https://github.com/apache/hbase/pull/3356#discussion_r657546722



##########
File path: 
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/StochasticLoadBalancer.java
##########
@@ -319,38 +318,33 @@ boolean needsBalance(TableName tableName, 
BalancerClusterState cluster) {
       return true;
     }
 
+    sumMultiplier = 0.0f;
     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;
-      }
+      double cost = c.cost();
       if (!c.isNeeded()) {
         LOG.trace("{} not needed", c.getClass().getSimpleName());
         continue;
       }
+      total += cost * multiplier;
       sumMultiplier += multiplier;
-      total += c.cost() * multiplier;
     }
 
-    boolean balanced = total <= 0 || sumMultiplier <= 0 ||
-        (sumMultiplier > 0 && (total / sumMultiplier) < minCostNeedBalance);
+    boolean balanced = (total / sumMultiplier < minCostNeedBalance);
+
     if (balanced) {
       final double calculatedTotal = total;
-      final double calculatedMultiplier = sumMultiplier;
-      sendRejectionReasonToRingBuffer(() -> getBalanceReason(calculatedTotal, 
calculatedMultiplier),
-        costFunctions);
-    }
-    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());
-      }
+      sendRejectionReasonToRingBuffer(() -> getBalanceReason(calculatedTotal), 
costFunctions);
+      LOG.info("{} - skipping load balancing because weighted average 
imbalance={} > threshold({})."
+          + "functionCost={}."
+          + "If you want more aggressive balancing, either lower 
minCostNeedbalance {}"
+          + "or increase the relative weight(s) of the specific cost 
function(s).",
+        isByTable ? "Table specific ("+tableName+")" : "Cluster wide", 
functionCost(),
+        total / sumMultiplier, minCostNeedBalance);

Review comment:
       Updated log from test run:  skipping load balancing because weighted 
average imbalance=RegionCountSkewCostFunction : (multiplier=500.0, 
imbalance=0.0, balanced); PrimaryRegionCountSkewCostFunction : (not needed); 
MoveCostFunction : (multiplier=7.0, imbalance=0.0, balanced); 
RackLocalityCostFunction : (multiplier=15.0, imbalance=0.0, balanced); 
TableSkewCostFunction : (multiplier=35.0, imbalance=1.0); 
RegionReplicaHostCostFunction : (not needed); RegionReplicaRackCostFunction : 
(not needed); ReadRequestCostFunction : (multiplier=5.0, imbalance=0.0, 
balanced); CPRequestCostFunction : (multiplier=5.0, imbalance=0.0, balanced); 
WriteRequestCostFunction : (multiplier=5.0, imbalance=0.0, balanced); 
MemStoreSizeCostFunction : (multiplier=5.0, imbalance=0.0, balanced); 
StoreFileCostFunction : (multiplier=5.0, imbalance=0.0, balanced);  > 
threshold(0.06013745704467354).functionCost=1.0. If you want more aggressive 
balancing, either lower hbase.master.balancer.stochastic.minCostNeedBala
 nce from {}or increase the relative multiplier(s) of the specific cost 
function(s)




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