add cluster balance indicator

include/dsn/utility/stddev.h

@@ -7,9 +7,9 @@
 #include <vector>
 
 namespace dsn {
-namespace stddev {
+namespace math {
 
 double mean_stddev(const std::vector<unsigned> &result_set, bool partial_sample);
 
-} // namespace stddev
+} // namespace math
 } // namespace dsn

src/core/core/stddev.cpp

@@ -8,7 +8,7 @@
 #include <dsn/utility/stddev.h>
 
 namespace dsn {
-namespace stddev {
+namespace math {
 
 double mean_stddev(const std::vector<unsigned> &result_set, bool partial_sample)
 {
@@ -30,5 +30,5 @@ double mean_stddev(const std::vector<unsigned> &result_set, bool partial_sample)
     return stddev;
 }
 
-} // namespace stddev
+} // namespace math
 } // namespace dsn

src/dist/replication/meta_server/greedy_load_balancer.cpp

@@ -199,8 +199,8 @@ void greedy_load_balancer::score(meta_view view, double &primary_stddev, double
     if (primary_count.size() <= 1 || partition_count.size() <= 1)
         return;
 
-    primary_stddev = stddev::mean_stddev(primary_count, partial_sample);
-    total_stddev = stddev::mean_stddev(partition_count, partial_sample);
+    primary_stddev = math::mean_stddev(primary_count, partial_sample);
+    total_stddev = math::mean_stddev(partition_count, partial_sample);
 }
 
 std::shared_ptr<configuration_balancer_request>

src/dist/replication/test/meta_test/unit_test/balancer_validator.cpp

@@ -229,6 +229,7 @@ void meta_service_test_app::balancer_validator()
 
         // iterate 1000000 times
         for (int i = 0; i < 1000000 && lb->balance({&apps, &nodes}, ml); ++i) {
+            dinfo("the %dth round of balancer", i);
             migration_check_and_apply(apps, nodes, ml, &manager);
             lb->check({&apps, &nodes}, ml);
             dinfo("balance checker operation count = %d", ml.size());
@@ -327,6 +328,7 @@ void meta_service_test_app::balance_config_file()
 
         // iterate 1000 times
         for (int i = 0; i < 1000 && lb->balance({&apps, &nodes}, ml); ++i) {
+            dinfo("the %dth round of balancer", i);
             migration_check_and_apply(apps, nodes, ml, nullptr);
             lb->check({&apps, &nodes}, ml);
             dinfo("balance checker operation count = %d", ml.size());