INT-3653: Fix Mean Calculations

JIRA: https://jira.spring.io/browse/INT-3653

After moving to nanosecond precision, the mean calculations were incorrect.

Add test cases to verify correctness.

spring-integration-core/src/main/java/org/springframework/integration/support/management/ExponentialMovingAverageRate.java

@@ -124,7 +124,7 @@ public class ExponentialMovingAverageRate {
 		}
 		long delta = System.nanoTime() - t0;
 		double value = delta > 0 ? delta / period : 0;
-		return count / (count / rates.getMeanNanos() + value);
+		return count / (count / rates.getMean() + value);
 	}
 
 	/**

spring-integration-core/src/main/java/org/springframework/integration/support/management/ExponentialMovingAverageRatio.java

@@ -95,7 +95,7 @@ public class ExponentialMovingAverageRatio {
 		t0 = t;
 		sum = alpha * sum + value;
 		weight = alpha * weight + 1;
-		cumulative.appendNanos(sum / weight);
+		cumulative.append(sum / weight);
 	}
 
 	/**
@@ -130,7 +130,7 @@ public class ExponentialMovingAverageRatio {
 		}
 		long t = System.nanoTime();
 		double alpha = Math.exp((t0 - t) / 1000000. * lapse);
-		return alpha * cumulative.getMeanNanos() + 1 - alpha;
+		return alpha * cumulative.getMean() + 1 - alpha;
 	}
 
 	/**

spring-integration-core/src/test/java/org/springframework/integration/support/management/ExponentialMovingAverageRateTests.java

@@ -22,6 +22,7 @@ import org.junit.Ignore;
 import org.junit.Test;
 
 import org.springframework.integration.test.util.TestUtils;
+import org.springframework.util.StopWatch;
 
 /**
  * @author Dave Syer
@@ -126,4 +127,18 @@ public class ExponentialMovingAverageRateTests {
 		assertEquals(0, history.getMax(), 0.01);
 	}
 
+	@Test
+	public void testRate() {
+		ExponentialMovingAverageRate rate = new ExponentialMovingAverageRate(1, 60, 10);
+		int count = 1000000;
+		StopWatch watch = new StopWatch();
+		watch.start();
+		for (int i = 0; i < count; i++) {
+			rate.increment();
+		}
+		watch.stop();
+		double calculatedRate = count / (double) watch.getTotalTimeMillis() * 1000;
+		assertEquals(calculatedRate, rate.getMean(), 2000000);
+	}
+
 }

spring-integration-core/src/test/java/org/springframework/integration/support/management/ExponentialMovingAverageRatioTests.java

@@ -130,4 +130,19 @@ public class ExponentialMovingAverageRatioTests {
 		return sum / count;
 	}
 
+	@Test
+	public void testRatio() {
+		ExponentialMovingAverageRatio ratio = new ExponentialMovingAverageRatio(60, 10);
+		for (int i = 0; i < 10000; i++) {
+			if (i % 10 == 0) {
+				ratio.failure();
+			}
+			else {
+				ratio.success();
+			}
+		}
+		assertEquals(0.9, ratio.getMax(), 0.01);
+		assertEquals(0.9, ratio.getMean(), 0.01);
+	}
+
 }

spring-integration-core/src/test/java/org/springframework/integration/support/management/ExponentialMovingAverageTests.java

@@ -65,4 +65,26 @@ public class ExponentialMovingAverageTests {
 		assertEquals(String.format("[N=%d, min=%f, max=%f, mean=%f, sigma=%f]", 0, 0d, 0d, 0d, 0d), history.toString());
 	}
 
+	@Test
+	public void testAv() throws Exception {
+		ExponentialMovingAverage av = new ExponentialMovingAverage(10);
+		for (int i = 0; i < 10000; i++) {
+			switch (i % 3) {
+				case 0:
+					av.appendNanos(20000);
+					break;
+				case 1:
+					av.appendNanos(30000);
+					break;
+				case 2:
+					av.appendNanos(40000);
+					break;
+			}
+		}
+		assertEquals(0.04, av.getMax(), 0.001);
+		assertEquals(0.02, av.getMin(), 0.001);
+		assertEquals(0.03, av.getMean(), 0.001);
+	}
+
+
 }