Update Golang test app to generate telemetry data

Author: IshwarKanse

tests/test-e2e-apps/golang/Dockerfile

@@ -1,8 +1,30 @@
-FROM golang:1.23-alpine as builder
+# Stage 1: Build the Go application
+FROM golang:1.23.0-alpine AS builder
 
+# Set the working directory inside the container for the build stage.
+WORKDIR /app
+
+# Copy the Go source file into the working directory inside the container.
 COPY main.go .
-RUN CGO_ENABLED=0 GOOS=linux GO111MODULE=on go build -o app main.go
 
+# Build the Go application.
+# - CGO_ENABLED=0: Disables CGO, which is necessary to build a statically linked binary
+#   that can run in a minimal 'scratch' image without external C libraries.
+# - GOOS=linux: Explicitly sets the target operating system to Linux, which is standard for containers.
+# -o /app/rolldice: Specifies the output path and name for the compiled executable inside this builder stage.
+# main.go: The source file to compile.
+RUN CGO_ENABLED=0 GOOS=linux go build -ldflags="-w -s" -o /app/rolldice main.go
+
+# Stage 2: Create the final minimal production image
 FROM scratch
-COPY --from=builder /go/app .
-ENTRYPOINT ["./app"]
+
+# Set the working directory for the final image.
+WORKDIR /
+
+# Copy only the compiled binary from the 'builder' stage (/app/rolldice)
+# into the root directory of the final 'scratch' image.
+COPY --from=builder /app/rolldice /rolldice
+
+# Set the command to run when the container starts.
+# This executes the compiled Go binary we copied into the image.
+ENTRYPOINT ["/rolldice"]

tests/test-e2e-apps/golang/main.go

@@ -4,23 +4,106 @@
 package main
 
 import (
+	"crypto/rand"
 	"fmt"
+	"log"
+	"math/big"
 	"net/http"
+	"os"
+	"strconv"
 	"time"
 )
 
+// getRandomNumber generates a random integer between min and max (inclusive).
+func getRandomNumber(min, max int) (int, error) {
+	if min > max {
+		return 0, fmt.Errorf("min (%d) cannot be greater than max (%d)", min, max)
+	}
+
+	// Calculate the range size.
+	rangeSize := big.NewInt(int64(max - min + 1))
+
+	// Generate a random number n, where 0 <= n < rangeSize.
+	n, err := rand.Int(rand.Reader, rangeSize)
+	if err != nil {
+		// Return an error if random number generation fails
+		return 0, fmt.Errorf("failed to generate random number: %w", err)
+	}
+
+	// Convert the big.Int result back to a regular int.
+	// Add min to shift the range from [0, rangeSize) to [min, max].
+	// n.Int64() is safe here because rangeSize fits in int64 if max-min+1 does.
+	result := int(n.Int64()) + min
+	return result, nil
+}
+
+// rollDiceHandler handles requests to the /rolldice endpoint.
+func rollDiceHandler(w http.ResponseWriter, r *http.Request) {
+	// Ensure we only handle GET requests for this endpoint
+	if r.Method != http.MethodGet {
+		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	// Generate a random number between 1 and 6
+	diceRoll, err := getRandomNumber(1, 6)
+	if err != nil {
+		// Log the error and return an internal server error if generation failed
+		log.Printf("Error generating random number: %v", err)
+		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
+		return
+	}
+
+	// Convert the integer result to a string
+	responseString := strconv.Itoa(diceRoll)
+
+	// Set the content type header to text/plain
+	w.Header().Set("Content-Type", "text/plain")
+
+	// Write the string response back to the client
+	_, writeErr := fmt.Fprint(w, responseString)
+	if writeErr != nil {
+		// Log the error if writing the response failed (response may be partially sent)
+		log.Printf("Error writing response: %v", writeErr)
+		// Attempt to send an error, though headers might already be sent
+		// http.Error(w, "Internal Server Error", http.StatusInternalServerError) // Avoid sending second error
+	}
+	log.Printf("Rolled a %d for request from %s", diceRoll, r.RemoteAddr) // Optional: Log the roll
+}
+
 func main() {
-	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
-		fmt.Println("Hi")
-	})
+	// Get the port from the environment variable, default to "8095" if not set
+	port := os.Getenv("PORT")
+	if port == "" {
+		port = "8095"
+	}
+
+	// Register the handler function for the "/rolldice" path with the DefaultServeMux.
+	http.HandleFunc("/rolldice", rollDiceHandler)
+
+	// Construct the server address string (e.g., ":8095")
+	serverAddr := ":" + port
 
+	// Configure the HTTP server with timeouts
 	server := &http.Server{
-		Addr:              ":8080",
-		ReadHeaderTimeout: 3 * time.Second,
+		Addr: serverAddr,
+		// Use DefaultServeMux by leaving Handler nil, which includes our /rolldice handler
+		Handler:      nil,
+		ReadTimeout:  10 * time.Second, // Max time to read entire request, including body
+		WriteTimeout: 10 * time.Second, // Max time to write response
+		IdleTimeout:  60 * time.Second, // Max time for connections using TCP Keep-Alive
 	}
 
+	// Print a message indicating the server is starting
+	log.Printf("Listening for requests on http://localhost:%s", port)
+
+	// Start the configured HTTP server.
+	// This ListenAndServe is now called on our configured server instance.
 	err := server.ListenAndServe()
-	if err != nil {
-		panic(err)
+	if err != nil && err != http.ErrServerClosed {
+		// Log any fatal errors encountered during server startup, ignore ErrServerClosed
+		log.Fatalf("Server failed to start or unexpectedly closed: %v", err)
+	} else if err == http.ErrServerClosed {
+		log.Println("Server shut down gracefully")
 	}
 }