Merge pull request #183 from deploymenttheory/dev

Adjust response time variability threshold and concurrency logic in t…

Author: ShocOne

concurrency/const.go

@@ -54,4 +54,9 @@ const (
 	// high. If response times exceed this threshold, it could signal that the system or the external service
 	// is under heavy load and may benefit from scaling down concurrency to alleviate pressure.
 	ResponseTimeCriticalThreshold = 2 * time.Second
+
+	debounceScaleDownThreshold = 5 // Number of consecutive triggers before scaling down
+
+	//
+	AcceptableAverageResponseTime = 100 * time.Millisecond
 )

concurrency/metrics.go

@@ -5,6 +5,7 @@ import (
 	"math"
 	"net/http"
 	"strconv"
+	"sync"
 	"time"
 
 	"go.uber.org/zap"
@@ -194,39 +195,47 @@ func (ch *ConcurrencyHandler) MonitorServerResponseCodes(resp *http.Response) in
 
 // A slice to hold the last n response times for averaging
 var responseTimes []time.Duration
+var responseTimesLock sync.Mutex
 
+// MonitorResponseTimeVariability monitors the response time variability and suggests a concurrency adjustment.
 // MonitorResponseTimeVariability monitors the response time variability and suggests a concurrency adjustment.
 func (ch *ConcurrencyHandler) MonitorResponseTimeVariability(responseTime time.Duration) int {
-	ch.Metrics.Lock.Lock() // Ensure thread safety when accessing shared metrics
-	defer ch.Metrics.Lock.Unlock()
+	ch.Metrics.ResponseTimeVariability.Lock.Lock()
+	defer ch.Metrics.ResponseTimeVariability.Lock.Unlock()
 
-	// Append the latest response time
+	responseTimesLock.Lock() // Ensure safe concurrent access
 	responseTimes = append(responseTimes, responseTime)
-	if len(responseTimes) > 10 { // Use the last 10 measurements for a smoother average
-		responseTimes = responseTimes[1:]
+	if len(responseTimes) > 10 {
+		responseTimes = responseTimes[1:] // Maintain last 10 measurements
 	}
+	responseTimesLock.Unlock()
 
 	stdDev := calculateStdDev(responseTimes)
+	averageResponseTime := calculateAverage(responseTimes)
 
-	// Action determination with debounce effect
-	// Debounce mechanism for scaling down
-	const debounceCount = 3 // Threshold must be exceeded in 3 consecutive checks to act
-	if stdDev > (ch.Metrics.ResponseTimeVariability.StdDevThreshold * 2) {
+	// Multi-factor check before scaling down
+	if stdDev > ch.Metrics.ResponseTimeVariability.StdDevThreshold && averageResponseTime > AcceptableAverageResponseTime {
 		ch.Metrics.ResponseTimeVariability.DebounceScaleDownCount++
-		ch.logger.Info("Increased debounce counter", zap.Int("counter", ch.Metrics.ResponseTimeVariability.DebounceScaleDownCount))
-		if ch.Metrics.ResponseTimeVariability.DebounceScaleDownCount >= debounceCount {
-			ch.Metrics.ResponseTimeVariability.DebounceScaleDownCount = 0 // reset counter after action
-			ch.logger.Info("Concurrent requests scaling down due to high response time variability")
+		if ch.Metrics.ResponseTimeVariability.DebounceScaleDownCount >= debounceScaleDownThreshold {
+			ch.Metrics.ResponseTimeVariability.DebounceScaleDownCount = 0
 			return -1 // Suggest decrease concurrency
 		}
 	} else {
-		ch.Metrics.ResponseTimeVariability.DebounceScaleDownCount = 0 // reset counter if condition not met
-		if stdDev <= ch.Metrics.ResponseTimeVariability.StdDevThreshold && len(ch.sem) < cap(ch.sem) {
-			ch.logger.Info("Concurrent requests scaling up as conditions are favorable")
-			return 1 // Suggest increase concurrency if there is capacity
+		ch.Metrics.ResponseTimeVariability.DebounceScaleDownCount = 0 // Reset counter if conditions are not met
+		if stdDev <= ch.Metrics.ResponseTimeVariability.StdDevThreshold {
+			return 1 // Suggest increase concurrency if conditions are favorable
 		}
 	}
-	return 0
+	return 0 // Default to no change
+}
+
+// calculateAverage computes the average response time from a slice of response times.
+func calculateAverage(times []time.Duration) time.Duration {
+	var total time.Duration
+	for _, t := range times {
+		total += t
+	}
+	return total / time.Duration(len(times))
 }
 
 // calculateStdDev computes the standard deviation of response times.