fix linter

Signed-off-by: Musilah <nataleigh.nk@gmail.com>

Author: Musilah

cmd/main.go

@@ -36,6 +36,8 @@ const (
 
 	coapWithoutDTLS = "MPROXY_COAP_WITHOUT_DTLS_"
 	coapWithDTLS    = "MPROXY_COAP_WITH_DTLS_"
+
+	defaultTargetHost = "localhost"
 )
 
 func main() {
@@ -136,7 +138,7 @@ func startMQTTProxy(g *errgroup.Group, ctx context.Context, envPrefix string, ha
 	}
 
 	if cfg.TargetHost == "" {
-		cfg.TargetHost = "localhost"
+		cfg.TargetHost = defaultTargetHost
 	}
 
 	if cfg.TargetPort == "" {
@@ -187,7 +189,7 @@ func startWebSocketProxy(g *errgroup.Group, ctx context.Context, envPrefix strin
 	}
 
 	if cfg.TargetHost == "" {
-		cfg.TargetHost = "localhost"
+		cfg.TargetHost = defaultTargetHost
 	}
 
 	if cfg.TargetPort == "" {
@@ -245,7 +247,7 @@ func startHTTPProxy(g *errgroup.Group, ctx context.Context, envPrefix string, ha
 	}
 
 	if cfg.TargetHost == "" {
-		cfg.TargetHost = "localhost"
+		cfg.TargetHost = defaultTargetHost
 	}
 
 	if cfg.TargetPort == "" {
@@ -300,7 +302,7 @@ func startCoAPProxy(g *errgroup.Group, ctx context.Context, envPrefix string, ha
 	}
 
 	if cfg.TargetHost == "" {
-		cfg.TargetHost = "localhost"
+		cfg.TargetHost = defaultTargetHost
 	}
 
 	if cfg.TargetPort == "" {

cmd/production/handlers.go

@@ -13,6 +13,8 @@ import (
 	"github.com/absmach/mproxy/pkg/ratelimit"
 )
 
+const protocolMQTT = "mqtt"
+
 // RateLimitedHandler wraps a handler with rate limiting.
 type RateLimitedHandler struct {
 	handler          handler.Handler
@@ -97,13 +99,10 @@ type InstrumentedHandler struct {
 func (h *InstrumentedHandler) AuthConnect(ctx context.Context, hctx *handler.Context) error {
 	start := time.Now()
 	h.metrics.AuthAttempts.WithLabelValues(hctx.Protocol, "connect").Inc()
-
 	err := h.handler.AuthConnect(ctx, hctx)
-
 	if err != nil {
 		h.metrics.AuthFailures.WithLabelValues(hctx.Protocol, "connect", "unauthorized").Inc()
 	}
-
 	duration := time.Since(start).Seconds()
 	h.metrics.RequestDuration.WithLabelValues(hctx.Protocol, "connect").Observe(duration)
 
@@ -114,17 +113,13 @@ func (h *InstrumentedHandler) AuthConnect(ctx context.Context, hctx *handler.Con
 func (h *InstrumentedHandler) AuthPublish(ctx context.Context, hctx *handler.Context, topic *string, payload *[]byte) error {
 	start := time.Now()
 	h.metrics.AuthAttempts.WithLabelValues(hctx.Protocol, "publish").Inc()
-
 	if payload != nil {
 		h.metrics.RequestSize.WithLabelValues(hctx.Protocol).Observe(float64(len(*payload)))
 	}
-
 	err := h.handler.AuthPublish(ctx, hctx, topic, payload)
-
 	if err != nil {
 		h.metrics.AuthFailures.WithLabelValues(hctx.Protocol, "publish", "unauthorized").Inc()
 	}
-
 	duration := time.Since(start).Seconds()
 	h.metrics.RequestDuration.WithLabelValues(hctx.Protocol, "publish").Observe(duration)
 
@@ -141,13 +136,10 @@ func (h *InstrumentedHandler) AuthPublish(ctx context.Context, hctx *handler.Con
 func (h *InstrumentedHandler) AuthSubscribe(ctx context.Context, hctx *handler.Context, topics *[]string) error {
 	start := time.Now()
 	h.metrics.AuthAttempts.WithLabelValues(hctx.Protocol, "subscribe").Inc()
-
 	err := h.handler.AuthSubscribe(ctx, hctx, topics)
-
 	if err != nil {
 		h.metrics.AuthFailures.WithLabelValues(hctx.Protocol, "subscribe", "unauthorized").Inc()
 	}
-
 	duration := time.Since(start).Seconds()
 	h.metrics.RequestDuration.WithLabelValues(hctx.Protocol, "subscribe").Observe(duration)
 
@@ -170,7 +162,7 @@ func (h *InstrumentedHandler) OnConnect(ctx context.Context, hctx *handler.Conte
 
 // OnPublish implements handler.Handler with metrics.
 func (h *InstrumentedHandler) OnPublish(ctx context.Context, hctx *handler.Context, topic string, payload []byte) error {
-	if hctx.Protocol == "mqtt" {
+	if hctx.Protocol == protocolMQTT {
 		h.metrics.MQTTPackets.WithLabelValues("publish", "upstream").Inc()
 	}
 
@@ -179,7 +171,7 @@ func (h *InstrumentedHandler) OnPublish(ctx context.Context, hctx *handler.Conte
 
 // OnSubscribe implements handler.Handler with metrics.
 func (h *InstrumentedHandler) OnSubscribe(ctx context.Context, hctx *handler.Context, topics []string) error {
-	if hctx.Protocol == "mqtt" {
+	if hctx.Protocol == protocolMQTT {
 		h.metrics.MQTTPackets.WithLabelValues("subscribe", "upstream").Inc()
 	}
 
@@ -188,7 +180,7 @@ func (h *InstrumentedHandler) OnSubscribe(ctx context.Context, hctx *handler.Con
 
 // OnUnsubscribe implements handler.Handler with metrics.
 func (h *InstrumentedHandler) OnUnsubscribe(ctx context.Context, hctx *handler.Context, topics []string) error {
-	if hctx.Protocol == "mqtt" {
+	if hctx.Protocol == protocolMQTT {
 		h.metrics.MQTTPackets.WithLabelValues("unsubscribe", "upstream").Inc()
 	}
 

cmd/production/main.go

@@ -30,27 +30,29 @@ import (
 	"golang.org/x/sync/errgroup"
 )
 
+const logError = "error"
+
 // Config holds the application configuration.
 type Config struct {
 	// Observability
-	MetricsPort  int    `env:"METRICS_PORT"  envDefault:"9090"`
-	HealthPort   int    `env:"HEALTH_PORT"   envDefault:"8080"`
-	LogLevel     string `env:"LOG_LEVEL"     envDefault:"info"`
-	LogFormat    string `env:"LOG_FORMAT"    envDefault:"json"`
+	MetricsPort int    `env:"METRICS_PORT"  envDefault:"9090"`
+	HealthPort  int    `env:"HEALTH_PORT"   envDefault:"8080"`
+	LogLevel    string `env:"LOG_LEVEL"     envDefault:"info"`
+	LogFormat   string `env:"LOG_FORMAT"    envDefault:"json"`
 
 	// Resource Limits
-	MaxConnections  int `env:"MAX_CONNECTIONS"  envDefault:"10000"`
-	MaxGoroutines   int `env:"MAX_GOROUTINES"   envDefault:"50000"`
+	MaxConnections int `env:"MAX_CONNECTIONS"  envDefault:"10000"`
+	MaxGoroutines  int `env:"MAX_GOROUTINES"   envDefault:"50000"`
 
 	// Connection Pooling
 	PoolMaxIdle     int           `env:"POOL_MAX_IDLE"      envDefault:"100"`
 	PoolMaxActive   int           `env:"POOL_MAX_ACTIVE"    envDefault:"1000"`
 	PoolIdleTimeout time.Duration `env:"POOL_IDLE_TIMEOUT"  envDefault:"5m"`
 
 	// Circuit Breaker
-	BreakerMaxFailures   int           `env:"BREAKER_MAX_FAILURES"   envDefault:"5"`
-	BreakerResetTimeout  time.Duration `env:"BREAKER_RESET_TIMEOUT"  envDefault:"60s"`
-	BreakerTimeout       time.Duration `env:"BREAKER_TIMEOUT"        envDefault:"30s"`
+	BreakerMaxFailures  int           `env:"BREAKER_MAX_FAILURES"   envDefault:"5"`
+	BreakerResetTimeout time.Duration `env:"BREAKER_RESET_TIMEOUT"  envDefault:"60s"`
+	BreakerTimeout      time.Duration `env:"BREAKER_TIMEOUT"        envDefault:"30s"`
 
 	// Rate Limiting
 	RateLimitCapacity  int64 `env:"RATE_LIMIT_CAPACITY"   envDefault:"100"`
@@ -70,14 +72,20 @@ type Config struct {
 }
 
 func main() {
+	if err := run(); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
+
+func run() error {
 	// Load configuration
 	cfg := Config{}
 	if err := godotenv.Load(); err != nil {
 		// .env file is optional
 	}
 	if err := env.Parse(&cfg); err != nil {
-		fmt.Fprintf(os.Stderr, "Failed to parse config: %v\n", err)
-		os.Exit(1)
+		return fmt.Errorf("failed to parse config: %w", err)
 	}
 
 	// Setup logger
@@ -216,7 +224,7 @@ func main() {
 
 	mqttProxy, err := proxy.NewMQTT(mqttProxyConfig, instrumentedHandler)
 	if err != nil {
-		logger.Error("Failed to create MQTT proxy", slog.String("error", err.Error()))
+		logger.Error("Failed to create MQTT proxy", slog.String(logError, err.Error()))
 	} else {
 		g.Go(func() error {
 			address := net.JoinHostPort(mqttProxyConfig.Host, mqttProxyConfig.Port)
@@ -246,21 +254,22 @@ func main() {
 	shutdownCtx, shutdownCancel := context.WithTimeout(context.Background(), cfg.ShutdownTimeout)
 	defer shutdownCancel()
 
-	done := make(chan error)
+	done := make(chan error, 1)
 	go func() {
 		done <- g.Wait()
 	}()
 
 	select {
 	case err := <-done:
 		if err != nil {
-			logger.Error("Shutdown error", slog.String("error", err.Error()))
-			os.Exit(1)
+			logger.Error("Shutdown error", slog.String(logError, err.Error()))
+			return err
 		}
 		logger.Info("Graceful shutdown completed")
+		return nil
 	case <-shutdownCtx.Done():
 		logger.Warn("Shutdown timeout exceeded, forcing exit")
-		os.Exit(1)
+		return shutdownCtx.Err()
 	}
 }
 
@@ -274,7 +283,7 @@ func setupLogger(level, format string) *slog.Logger {
 		logLevel = slog.LevelInfo
 	case "warn":
 		logLevel = slog.LevelWarn
-	case "error":
+	case logError:
 		logLevel = slog.LevelError
 	default:
 		logLevel = slog.LevelInfo
@@ -311,7 +320,7 @@ func startMetricsServer(port int, logger *slog.Logger) {
 	}
 
 	if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
-		logger.Error("Metrics server error", slog.String("error", err.Error()))
+		logger.Error("Metrics server error", slog.String(logError, err.Error()))
 	}
 }
 
@@ -334,6 +343,6 @@ func startHealthServer(port int, checker *health.Checker, logger *slog.Logger) {
 	}
 
 	if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
-		logger.Error("Health server error", slog.String("error", err.Error()))
+		logger.Error("Health server error", slog.String(logError, err.Error()))
 	}
 }

pkg/breaker/breaker.go

@@ -10,10 +10,8 @@ import (
 	"time"
 )
 
-var (
-	// ErrCircuitOpen is returned when the circuit breaker is open.
-	ErrCircuitOpen = errors.New("circuit breaker is open")
-)
+// ErrCircuitOpen is returned when the circuit breaker is open.
+var ErrCircuitOpen = errors.New("circuit breaker is open")
 
 // State represents the circuit breaker state.
 type State int
@@ -51,14 +49,14 @@ type Config struct {
 
 // CircuitBreaker implements the circuit breaker pattern.
 type CircuitBreaker struct {
-	mu               sync.RWMutex
-	config           Config
-	state            State
-	failures         int
-	successes        int
-	lastFailureTime  time.Time
-	lastStateChange  time.Time
-	onStateChange    func(from, to State)
+	mu              sync.RWMutex
+	config          Config
+	state           State
+	failures        int
+	successes       int
+	lastFailureTime time.Time
+	lastStateChange time.Time
+	onStateChange   func(from, to State)
 }
 
 // New creates a new circuit breaker.

pkg/errors/errors.go

@@ -9,7 +9,7 @@ import (
 	"fmt"
 )
 
-// Common error types
+// Common error types.
 var (
 	// ErrUnauthorized indicates authentication or authorization failure.
 	ErrUnauthorized = errors.New("unauthorized")
@@ -41,11 +41,11 @@ var (
 
 // ProxyError wraps an error with additional context.
 type ProxyError struct {
-	Op        string // Operation that failed
-	Protocol  string // Protocol (mqtt, http, coap, websocket)
-	SessionID string // Session identifier
+	Op         string // Operation that failed
+	Protocol   string // Protocol (mqtt, http, coap, websocket)
+	SessionID  string // Session identifier
 	RemoteAddr string // Client address
-	Err       error  // Underlying error
+	Err        error  // Underlying error
 }
 
 // Error implements the error interface.
@@ -67,11 +67,11 @@ func New(op, protocol, sessionID, remoteAddr string, err error) error {
 		return nil
 	}
 	return &ProxyError{
-		Op:        op,
-		Protocol:  protocol,
-		SessionID: sessionID,
+		Op:         op,
+		Protocol:   protocol,
+		SessionID:  sessionID,
 		RemoteAddr: remoteAddr,
-		Err:       err,
+		Err:        err,
 	}
 }
 

pkg/health/health.go

@@ -120,13 +120,13 @@ func (c *Checker) HTTPHandler() http.HandlerFunc {
 		w.Header().Set("Content-Type", "application/json")
 		if status == StatusUnhealthy {
 			w.WriteHeader(http.StatusServiceUnavailable)
-		} else if status == StatusDegraded {
-			w.WriteHeader(http.StatusOK) // Still accept traffic
 		} else {
-			w.WriteHeader(http.StatusOK)
+			w.WriteHeader(http.StatusOK) // Still accept traffic
 		}
 
-		json.NewEncoder(w).Encode(response)
+		if err := json.NewEncoder(w).Encode(response); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+		}
 	}
 }
 
@@ -135,9 +135,11 @@ func LivenessHandler() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "application/json")
 		w.WriteHeader(http.StatusOK)
-		json.NewEncoder(w).Encode(map[string]string{
+		if err := json.NewEncoder(w).Encode(map[string]string{
 			"status": "alive",
-		})
+		}); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+		}
 	}
 }
 
@@ -161,6 +163,8 @@ func (c *Checker) ReadinessHandler() http.HandlerFunc {
 			w.WriteHeader(http.StatusOK)
 		}
 
-		json.NewEncoder(w).Encode(response)
+		if err := json.NewEncoder(w).Encode(response); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+		}
 	}
 }