loadr/lib/metrics.go

package lib

import (
	"fmt"
	"math"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"time"
)

// Global metrics instance to track performance during load testing
var metrics = PerformanceMetrics{
	// Initialize MinLatency to the maximum possible duration
	MinLatency: time.Duration(math.MaxInt64),
	// Initialize response counters map
	ResponseCounters: make(map[int]int32),
}

// UpdateMetrics synchronously updates performance metrics for each request
//   - duration: time taken to complete the request
//   - resp: HTTP response from the request
//   - second: elapsed seconds since the start of the test
func UpdateMetrics(duration time.Duration, resp *http.Response, second int) {
	metrics.Mu.Lock()
	defer metrics.Mu.Unlock()

	// Increment total requests
	metrics.TotalRequests++
	// Add current request's latency to total
	metrics.TotalLatency += duration

	// Update maximum latency if current duration is higher
	if duration > metrics.MaxLatency {
		metrics.MaxLatency = duration
	}
	// Update minimum latency if current duration is lower
	if duration < metrics.MinLatency {
		metrics.MinLatency = duration
	}

	// Track successful responses
	if resp.StatusCode == http.StatusOK {
		metrics.TotalResponses++
		metrics.ResponseCounters[second]++
	}

	// Debug log of current metrics
	fmt.Printf("Current metrics - Total Requests: %d, Total Responses: %d\n",
		metrics.TotalRequests, metrics.TotalResponses)
}

// CalculateAndPrintMetrics generates a comprehensive report of load test performance
// Parameters:
//   - startTime: when the load test began
//   - requestsPerSecond: target request rate
//   - endpoint: URL being tested
//   - patterns: request patterns used in the test
func CalculateAndPrintMetrics(startTime time.Time, requestsPerSecond float64, endpoint string, patterns []RequestPattern) {
	// Small delay to ensure all metrics are captured
	time.Sleep(100 * time.Millisecond)

	metrics.Mu.Lock()
	defer metrics.Mu.Unlock()

	// Calculate average latency
	averageLatency := time.Duration(0)
	if metrics.TotalRequests > 0 {
		averageLatency = metrics.TotalLatency / time.Duration(metrics.TotalRequests)
	}

	// Calculate total test duration and total responses
	totalDuration := time.Since(startTime).Seconds()
	totalResponses := int32(0)
	for _, count := range metrics.ResponseCounters {
		totalResponses += count
	}

	// Ensure MinLatency is not left at its initial max value
	if metrics.MinLatency == time.Duration(math.MaxInt64) {
		metrics.MinLatency = 0
	}

	// Build detailed results string
	results := fmt.Sprintf("Load Test Report\n")
	results += fmt.Sprintf("=============\n\n")

	// Report endpoint and request pattern
	results += fmt.Sprintf("Endpoint: %s\n", endpoint)
	results += fmt.Sprintf("Pattern: ")

	for i, p := range patterns {
		if i > 0 {
			results += " → "
		}

		var patternDesc string
		if p.Percentage > 0 && p.Percentage < 100 {
			// Probabilistic pattern (e.g., "20%p80%g")
			patternDesc = fmt.Sprintf("%.0f%%%s", p.Percentage, strings.ToLower(p.Verb[:1]))
		} else {
			// Simple or sequential pattern (e.g., "5p", "3g", "1p5g")
			patternDesc = fmt.Sprintf("%d%s", p.Sequence, strings.ToLower(p.Verb[:1]))
		}

		results += patternDesc
	}
	results += "\n\n"

	// Detailed performance metrics
	results += fmt.Sprintf("Performance Metrics\n")
	results += fmt.Sprintf("-----------------\n")
	results += fmt.Sprintf("Total Requests Sent: %d\n", metrics.TotalRequests)
	results += fmt.Sprintf("Total Responses Received: %d\n", totalResponses)
	results += fmt.Sprintf("Average Latency: %s\n", averageLatency)
	results += fmt.Sprintf("Max Latency: %s\n", metrics.MaxLatency)
	results += fmt.Sprintf("Min Latency: %s\n", metrics.MinLatency)
	results += fmt.Sprintf("Requests/sec (Target): %.2f\n", requestsPerSecond)
	results += fmt.Sprintf("Requests/sec (Actual): %.2f\n", float64(metrics.TotalRequests)/totalDuration)
	results += fmt.Sprintf("Responses/sec: %.2f\n", float64(totalResponses)/totalDuration)

	// Print and save the report
	fmt.Println(results)
	saveReport(results)
}

// saveReport writes the load test results to a timestamped file in the .reports directory
// Parameters:
//   - results: formatted results string to be saved
func saveReport(results string) {
	// Ensure .reports directory exists
	resultsDir := ".reports"
	os.MkdirAll(resultsDir, os.ModePerm)

	// Create a unique filename based on current timestamp
	resultsFile := filepath.Join(resultsDir, fmt.Sprintf("%d.txt", time.Now().Unix()))

	// Write results to file
	if err := os.WriteFile(resultsFile, []byte(results), 0644); err != nil {
		fmt.Println("Error saving report:", err)
		return
	}

	fmt.Println("Report saved:", resultsFile)
}