optimize code structure to economize computing resources (#1536)

* 优化代码结构,减少不必要的计算,节省计算资源

* 优化代码结构,减少不必要的计算,节省计算资源

apm-collector/apm-collector-analysis/analysis-metric/metric-provider/src/main/java/org/apache/skywalking/apm/collector/analysis/metric/provider/worker/global/std/ResponseTimeDistributionSpanListener.java

@@ -73,15 +73,16 @@ public class ResponseTimeDistributionSpanListener implements FirstSpanListener {
     }
 
     int getStep(int duration) {
-        int countOfResponseTimeSteps = configService.getResponseTimeStep() * configService.getCountOfResponseTimeSteps();
         int responseTimeStep = configService.getResponseTimeStep();
+        int countOfResponseTimeSteps = configService.getCountOfResponseTimeSteps();
+        int totalTimeOfResponseTimeSteps = configService.getTotalTimeOfResponseTimeSteps();
 
-        if (duration > countOfResponseTimeSteps) {
-            return countOfResponseTimeSteps / responseTimeStep;
+        if (duration > totalTimeOfResponseTimeSteps) {
+            return countOfResponseTimeSteps;
         } else if (duration <= responseTimeStep) {
             return 0;
         } else {
-            return (int)Math.ceil((double)duration / (double)responseTimeStep) - 1;
+            return (int) Math.ceil((double) duration / (double) responseTimeStep) - 1;
         }
     }
 

apm-collector/apm-collector-analysis/analysis-metric/metric-provider/src/test/java/org/apache/skywalking/apm/collector/analysis/metric/provider/worker/global/std/ResponseTimeDistributionSpanListenerTestCase.java

@@ -42,6 +42,7 @@ public class ResponseTimeDistributionSpanListenerTestCase {
         IResponseTimeDistributionConfigService service = Mockito.mock(IResponseTimeDistributionConfigService.class);
         Mockito.when(service.getResponseTimeStep()).thenReturn(50);
         Mockito.when(service.getCountOfResponseTimeSteps()).thenReturn(40);
+        Mockito.when(service.getTotalTimeOfResponseTimeSteps()).thenReturn(2050);
 
         ModuleDefine module = Mockito.mock(ModuleDefine.class);
         Whitebox.setInternalState(module, "loadedProviders", loadedProviders);

apm-collector/apm-collector-configuration/collector-configuration-define/src/main/java/org/apache/skywalking/apm/collector/configuration/service/IResponseTimeDistributionConfigService.java

@@ -28,4 +28,12 @@ public interface IResponseTimeDistributionConfigService extends Service {
     int getResponseTimeStep();
 
     int getCountOfResponseTimeSteps();
+
+    /**
+     * Equals to getResponseTimeStep() * getCountOfResponseTimeSteps() ,just for economizes computing resources
+     *
+     * @return
+     */
+    int getTotalTimeOfResponseTimeSteps();
+
 }

apm-collector/apm-collector-configuration/collector-configuration-provider/src/main/java/org/apache/skywalking/apm/collector/configuration/service/ResponseTimeDistributionConfigService.java

@@ -25,10 +25,12 @@ public class ResponseTimeDistributionConfigService implements IResponseTimeDistr
 
     private final int responseTimeStep;
     private final int countOfResponseTimeSteps;
+    private final int totalTimeOfResponseTimeSteps;
 
     public ResponseTimeDistributionConfigService(int responseTimeStep, int countOfResponseTimeSteps) {
         this.responseTimeStep = responseTimeStep;
         this.countOfResponseTimeSteps = countOfResponseTimeSteps + 1;
+        this.totalTimeOfResponseTimeSteps = this.responseTimeStep * this.countOfResponseTimeSteps;
     }
 
     @Override public int getResponseTimeStep() {
@@ -38,4 +40,9 @@ public class ResponseTimeDistributionConfigService implements IResponseTimeDistr
     @Override public int getCountOfResponseTimeSteps() {
         return countOfResponseTimeSteps;
     }
+
+    @Override
+    public int getTotalTimeOfResponseTimeSteps() {
+        return totalTimeOfResponseTimeSteps;
+    }
 }