wip.

hitless.go

@@ -0,0 +1,416 @@
+package redis
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/redis/go-redis/v9/internal"
+	"github.com/redis/go-redis/v9/internal/hitless"
+	"github.com/redis/go-redis/v9/internal/pool"
+)
+
+// HitlessUpgradeConfig provides configuration for hitless upgrades
+type HitlessUpgradeConfig struct {
+	// Enabled controls whether hitless upgrades are active
+	Enabled bool
+
+	// TransitionTimeout is the increased timeout for connections during transitions
+	// (MIGRATING/FAILING_OVER). This should be longer than normal operation timeouts
+	// to account for the time needed to complete the transition.
+	// Default: 60 seconds
+	TransitionTimeout time.Duration
+
+	// CleanupInterval controls how often expired states are cleaned up
+	// Default: 30 seconds
+	CleanupInterval time.Duration
+}
+
+// DefaultHitlessUpgradeConfig returns the default configuration for hitless upgrades
+func DefaultHitlessUpgradeConfig() *HitlessUpgradeConfig {
+	return &HitlessUpgradeConfig{
+		Enabled:           true,
+		TransitionTimeout: 60 * time.Second, // Longer timeout for transitioning connections
+		CleanupInterval:   30 * time.Second, // How often to clean up expired states
+	}
+}
+
+// HitlessUpgradeStatistics provides statistics about ongoing upgrade operations
+type HitlessUpgradeStatistics struct {
+	ActiveConnections      int       // Total connections in transition
+	IsMoving               bool      // Whether pool is currently moving
+	MigratingConnections   int       // Connections in MIGRATING state
+	FailingOverConnections int       // Connections in FAILING_OVER state
+	Timestamp              time.Time // When these statistics were collected
+}
+
+// HitlessUpgradeStatus provides detailed status of all ongoing upgrades
+type HitlessUpgradeStatus struct {
+	ConnectionStates map[interface{}]interface{}
+	IsMoving         bool
+	NewEndpoint      string
+	Timestamp        time.Time
+}
+
+// HitlessIntegration provides the interface for hitless upgrade functionality
+type HitlessIntegration interface {
+	// IsEnabled returns whether hitless upgrades are currently enabled
+	IsEnabled() bool
+
+	// EnableHitlessUpgrades enables hitless upgrade functionality
+	EnableHitlessUpgrades()
+
+	// DisableHitlessUpgrades disables hitless upgrade functionality
+	DisableHitlessUpgrades()
+
+	// GetConnectionTimeout returns the appropriate timeout for a connection
+	// If the connection is transitioning, returns the longer TransitionTimeout
+	GetConnectionTimeout(conn interface{}, defaultTimeout time.Duration) time.Duration
+
+	// GetConnectionTimeouts returns both read and write timeouts for a connection
+	// If the connection is transitioning, returns increased timeouts
+	GetConnectionTimeouts(conn interface{}, defaultReadTimeout, defaultWriteTimeout time.Duration) (time.Duration, time.Duration)
+
+	// MarkConnectionAsBlocking marks a connection as having blocking commands
+	MarkConnectionAsBlocking(conn interface{}, isBlocking bool)
+
+	// IsConnectionMarkedForClosing checks if a connection should be closed
+	IsConnectionMarkedForClosing(conn interface{}) bool
+
+	// ShouldRedirectBlockingConnection checks if a blocking connection should be redirected
+	ShouldRedirectBlockingConnection(conn interface{}) (bool, string)
+
+	// GetUpgradeStatistics returns current upgrade statistics
+	GetUpgradeStatistics() *HitlessUpgradeStatistics
+
+	// GetUpgradeStatus returns detailed upgrade status
+	GetUpgradeStatus() *HitlessUpgradeStatus
+
+	// UpdateConfig updates the hitless upgrade configuration
+	UpdateConfig(config *HitlessUpgradeConfig) error
+
+	// GetConfig returns the current configuration
+	GetConfig() *HitlessUpgradeConfig
+
+	// Close shuts down the hitless integration
+	Close() error
+}
+
+// hitlessIntegrationImpl implements the HitlessIntegration interface
+type hitlessIntegrationImpl struct {
+	integration *hitless.RedisClientIntegration
+	mu          sync.RWMutex
+}
+
+// newHitlessIntegration creates a new hitless integration instance
+func newHitlessIntegration(config *HitlessUpgradeConfig) *hitlessIntegrationImpl {
+	if config == nil {
+		config = DefaultHitlessUpgradeConfig()
+	}
+
+	// Convert to internal config format
+	internalConfig := &hitless.HitlessUpgradeConfig{
+		Enabled:           config.Enabled,
+		TransitionTimeout: config.TransitionTimeout,
+		CleanupInterval:   config.CleanupInterval,
+	}
+
+	integration := hitless.NewRedisClientIntegration(internalConfig, 3*time.Second, 3*time.Second)
+
+	return &hitlessIntegrationImpl{
+		integration: integration,
+	}
+}
+
+// newHitlessIntegrationWithTimeouts creates a new hitless integration instance with timeout configuration
+func newHitlessIntegrationWithTimeouts(config *HitlessUpgradeConfig, defaultReadTimeout, defaultWriteTimeout time.Duration) *hitlessIntegrationImpl {
+	// Start with defaults
+	defaults := DefaultHitlessUpgradeConfig()
+
+	// If config is nil, use all defaults
+	if config == nil {
+		config = defaults
+	}
+
+	// Ensure all fields are set with defaults if they are zero values
+	enabled := config.Enabled
+	transitionTimeout := config.TransitionTimeout
+	cleanupInterval := config.CleanupInterval
+
+	// Apply defaults for zero values
+	if transitionTimeout == 0 {
+		transitionTimeout = defaults.TransitionTimeout
+	}
+	if cleanupInterval == 0 {
+		cleanupInterval = defaults.CleanupInterval
+	}
+
+	// Convert to internal config format with all fields properly set
+	internalConfig := &hitless.HitlessUpgradeConfig{
+		Enabled:           enabled,
+		TransitionTimeout: transitionTimeout,
+		CleanupInterval:   cleanupInterval,
+	}
+
+	integration := hitless.NewRedisClientIntegration(internalConfig, defaultReadTimeout, defaultWriteTimeout)
+
+	return &hitlessIntegrationImpl{
+		integration: integration,
+	}
+}
+
+// IsEnabled returns whether hitless upgrades are currently enabled
+func (h *hitlessIntegrationImpl) IsEnabled() bool {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+	return h.integration.IsEnabled()
+}
+
+// EnableHitlessUpgrades enables hitless upgrade functionality
+func (h *hitlessIntegrationImpl) EnableHitlessUpgrades() {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	h.integration.EnableHitlessUpgrades()
+}
+
+// DisableHitlessUpgrades disables hitless upgrade functionality
+func (h *hitlessIntegrationImpl) DisableHitlessUpgrades() {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	h.integration.DisableHitlessUpgrades()
+}
+
+// GetConnectionTimeout returns the appropriate timeout for a connection
+func (h *hitlessIntegrationImpl) GetConnectionTimeout(conn interface{}, defaultTimeout time.Duration) time.Duration {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+
+	// Convert interface{} to *pool.Conn
+	if poolConn, ok := conn.(*pool.Conn); ok {
+		return h.integration.GetConnectionTimeout(poolConn, defaultTimeout)
+	}
+
+	// If not a pool connection, return default timeout
+	return defaultTimeout
+}
+
+// GetConnectionTimeouts returns both read and write timeouts for a connection
+func (h *hitlessIntegrationImpl) GetConnectionTimeouts(conn interface{}, defaultReadTimeout, defaultWriteTimeout time.Duration) (time.Duration, time.Duration) {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+
+	// Convert interface{} to *pool.Conn
+	if poolConn, ok := conn.(*pool.Conn); ok {
+		return h.integration.GetConnectionTimeouts(poolConn, defaultReadTimeout, defaultWriteTimeout)
+	}
+
+	// If not a pool connection, return default timeouts
+	return defaultReadTimeout, defaultWriteTimeout
+}
+
+// MarkConnectionAsBlocking marks a connection as having blocking commands
+func (h *hitlessIntegrationImpl) MarkConnectionAsBlocking(conn interface{}, isBlocking bool) {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	// Convert interface{} to *pool.Conn
+	if poolConn, ok := conn.(*pool.Conn); ok {
+		h.integration.MarkConnectionAsBlocking(poolConn, isBlocking)
+	}
+}
+
+// IsConnectionMarkedForClosing checks if a connection should be closed
+func (h *hitlessIntegrationImpl) IsConnectionMarkedForClosing(conn interface{}) bool {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+
+	// Convert interface{} to *pool.Conn
+	if poolConn, ok := conn.(*pool.Conn); ok {
+		return h.integration.IsConnectionMarkedForClosing(poolConn)
+	}
+
+	return false
+}
+
+// ShouldRedirectBlockingConnection checks if a blocking connection should be redirected
+func (h *hitlessIntegrationImpl) ShouldRedirectBlockingConnection(conn interface{}) (bool, string) {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+
+	// Convert interface{} to *pool.Conn (can be nil for checking pool state)
+	var poolConn *pool.Conn
+	if conn != nil {
+		if pc, ok := conn.(*pool.Conn); ok {
+			poolConn = pc
+		}
+	}
+
+	return h.integration.ShouldRedirectBlockingConnection(poolConn)
+}
+
+// GetUpgradeStatistics returns current upgrade statistics
+func (h *hitlessIntegrationImpl) GetUpgradeStatistics() *HitlessUpgradeStatistics {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+
+	stats := h.integration.GetUpgradeStatistics()
+	if stats == nil {
+		return &HitlessUpgradeStatistics{Timestamp: time.Now()}
+	}
+
+	return &HitlessUpgradeStatistics{
+		ActiveConnections:      stats.ActiveConnections,
+		IsMoving:               stats.IsMoving,
+		MigratingConnections:   stats.MigratingConnections,
+		FailingOverConnections: stats.FailingOverConnections,
+		Timestamp:              stats.Timestamp,
+	}
+}
+
+// GetUpgradeStatus returns detailed upgrade status
+func (h *hitlessIntegrationImpl) GetUpgradeStatus() *HitlessUpgradeStatus {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+
+	status := h.integration.GetUpgradeStatus()
+	if status == nil {
+		return &HitlessUpgradeStatus{
+			ConnectionStates: make(map[interface{}]interface{}),
+			IsMoving:         false,
+			NewEndpoint:      "",
+			Timestamp:        time.Now(),
+		}
+	}
+
+	return &HitlessUpgradeStatus{
+		ConnectionStates: convertToInterfaceMap(status.ConnectionStates),
+		IsMoving:         status.IsMoving,
+		NewEndpoint:      status.NewEndpoint,
+		Timestamp:        status.Timestamp,
+	}
+}
+
+// UpdateConfig updates the hitless upgrade configuration
+func (h *hitlessIntegrationImpl) UpdateConfig(config *HitlessUpgradeConfig) error {
+	if config == nil {
+		return fmt.Errorf("config cannot be nil")
+	}
+
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	// Start with defaults for any zero values
+	defaults := DefaultHitlessUpgradeConfig()
+
+	// Ensure all fields are set with defaults if they are zero values
+	enabled := config.Enabled
+	transitionTimeout := config.TransitionTimeout
+	cleanupInterval := config.CleanupInterval
+
+	// Apply defaults for zero values
+	if transitionTimeout == 0 {
+		transitionTimeout = defaults.TransitionTimeout
+	}
+	if cleanupInterval == 0 {
+		cleanupInterval = defaults.CleanupInterval
+	}
+
+	// Convert to internal config format with all fields properly set
+	internalConfig := &hitless.HitlessUpgradeConfig{
+		Enabled:           enabled,
+		TransitionTimeout: transitionTimeout,
+		CleanupInterval:   cleanupInterval,
+	}
+
+	return h.integration.UpdateConfig(internalConfig)
+}
+
+// GetConfig returns the current configuration
+func (h *hitlessIntegrationImpl) GetConfig() *HitlessUpgradeConfig {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+
+	internalConfig := h.integration.GetConfig()
+	if internalConfig == nil {
+		return DefaultHitlessUpgradeConfig()
+	}
+
+	return &HitlessUpgradeConfig{
+		Enabled:           internalConfig.Enabled,
+		TransitionTimeout: internalConfig.TransitionTimeout,
+		CleanupInterval:   internalConfig.CleanupInterval,
+	}
+}
+
+// Close shuts down the hitless integration
+func (h *hitlessIntegrationImpl) Close() error {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	return h.integration.Close()
+}
+
+// getInternalIntegration returns the internal integration for use by Redis clients
+func (h *hitlessIntegrationImpl) getInternalIntegration() *hitless.RedisClientIntegration {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+	return h.integration
+}
+
+// ClientTimeoutProvider interface for extracting timeout configuration from client options
+type ClientTimeoutProvider interface {
+	GetReadTimeout() time.Duration
+	GetWriteTimeout() time.Duration
+}
+
+// optionsTimeoutProvider implements ClientTimeoutProvider for Options struct
+type optionsTimeoutProvider struct {
+	readTimeout  time.Duration
+	writeTimeout time.Duration
+}
+
+func (p *optionsTimeoutProvider) GetReadTimeout() time.Duration {
+	return p.readTimeout
+}
+
+func (p *optionsTimeoutProvider) GetWriteTimeout() time.Duration {
+	return p.writeTimeout
+}
+
+// newOptionsTimeoutProvider creates a timeout provider from Options
+func newOptionsTimeoutProvider(readTimeout, writeTimeout time.Duration) ClientTimeoutProvider {
+	return &optionsTimeoutProvider{
+		readTimeout:  readTimeout,
+		writeTimeout: writeTimeout,
+	}
+}
+
+// initializeHitlessIntegration initializes hitless integration for a client
+func initializeHitlessIntegration(client interface{}, config *HitlessUpgradeConfig, timeoutProvider ClientTimeoutProvider) (*hitlessIntegrationImpl, error) {
+	if config == nil || !config.Enabled {
+		return nil, nil
+	}
+
+	// Extract timeout configuration from client options
+	defaultReadTimeout := timeoutProvider.GetReadTimeout()
+	defaultWriteTimeout := timeoutProvider.GetWriteTimeout()
+
+	// Create hitless integration - each client gets its own instance
+	integration := newHitlessIntegrationWithTimeouts(config, defaultReadTimeout, defaultWriteTimeout)
+
+	// Push notification handlers are registered directly by the client
+	// No separate registration needed in simplified implementation
+
+	internal.Logger.Printf(context.Background(), "hitless: initialized hitless upgrades for client")
+
+	return integration, nil
+}
+
+// convertToInterfaceMap converts a typed map to interface{} map for public API
+func convertToInterfaceMap(input map[*pool.Conn]*hitless.ConnectionState) map[interface{}]interface{} {
+	result := make(map[interface{}]interface{})
+	for k, v := range input {
+		result[k] = v
+	}
+	return result
+}

hitless_config_defaults_test.go

@@ -0,0 +1,197 @@
+package redis
+
+import (
+	"testing"
+	"time"
+)
+
+func TestHitlessUpgradeConfig_DefaultValues(t *testing.T) {
+	tests := []struct {
+		name           string
+		inputConfig    *HitlessUpgradeConfig
+		expectedConfig *HitlessUpgradeConfig
+	}{
+		{
+			name:        "nil config should use all defaults",
+			inputConfig: nil,
+			expectedConfig: &HitlessUpgradeConfig{
+				Enabled:           true,
+				TransitionTimeout: 60 * time.Second,
+				CleanupInterval:   30 * time.Second,
+			},
+		},
+		{
+			name: "zero TransitionTimeout should use default",
+			inputConfig: &HitlessUpgradeConfig{
+				Enabled:           false,
+				TransitionTimeout: 0, // Zero value
+				CleanupInterval:   45 * time.Second,
+			},
+			expectedConfig: &HitlessUpgradeConfig{
+				Enabled:           false,
+				TransitionTimeout: 60 * time.Second, // Should use default
+				CleanupInterval:   45 * time.Second,
+			},
+		},
+		{
+			name: "zero CleanupInterval should use default",
+			inputConfig: &HitlessUpgradeConfig{
+				Enabled:           true,
+				TransitionTimeout: 90 * time.Second,
+				CleanupInterval:   0, // Zero value
+			},
+			expectedConfig: &HitlessUpgradeConfig{
+				Enabled:           true,
+				TransitionTimeout: 90 * time.Second,
+				CleanupInterval:   30 * time.Second, // Should use default
+			},
+		},
+		{
+			name: "both timeouts zero should use defaults",
+			inputConfig: &HitlessUpgradeConfig{
+				Enabled:           true,
+				TransitionTimeout: 0, // Zero value
+				CleanupInterval:   0, // Zero value
+			},
+			expectedConfig: &HitlessUpgradeConfig{
+				Enabled:           true,
+				TransitionTimeout: 60 * time.Second, // Should use default
+				CleanupInterval:   30 * time.Second, // Should use default
+			},
+		},
+		{
+			name: "all values set should be preserved",
+			inputConfig: &HitlessUpgradeConfig{
+				Enabled:           false,
+				TransitionTimeout: 120 * time.Second,
+				CleanupInterval:   60 * time.Second,
+			},
+			expectedConfig: &HitlessUpgradeConfig{
+				Enabled:           false,
+				TransitionTimeout: 120 * time.Second,
+				CleanupInterval:   60 * time.Second,
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Test with a mock client that has hitless upgrades enabled
+			opt := &Options{
+				Addr:                 "127.0.0.1:6379",
+				Protocol:             3,
+				HitlessUpgrades:      true,
+				HitlessUpgradeConfig: tt.inputConfig,
+				ReadTimeout:          5 * time.Second,
+				WriteTimeout:         5 * time.Second,
+			}
+
+			// Test the integration creation using the internal method directly
+			// since initializeHitlessIntegration requires a push processor
+			integration := newHitlessIntegrationWithTimeouts(tt.inputConfig, opt.ReadTimeout, opt.WriteTimeout)
+			if integration == nil {
+				t.Fatal("Integration should not be nil")
+			}
+
+			// Get the config from the integration
+			actualConfig := integration.GetConfig()
+			if actualConfig == nil {
+				t.Fatal("Config should not be nil")
+			}
+
+			// Verify all fields match expected values
+			if actualConfig.Enabled != tt.expectedConfig.Enabled {
+				t.Errorf("Enabled: expected %v, got %v", tt.expectedConfig.Enabled, actualConfig.Enabled)
+			}
+			if actualConfig.TransitionTimeout != tt.expectedConfig.TransitionTimeout {
+				t.Errorf("TransitionTimeout: expected %v, got %v", tt.expectedConfig.TransitionTimeout, actualConfig.TransitionTimeout)
+			}
+			if actualConfig.CleanupInterval != tt.expectedConfig.CleanupInterval {
+				t.Errorf("CleanupInterval: expected %v, got %v", tt.expectedConfig.CleanupInterval, actualConfig.CleanupInterval)
+			}
+
+			// Test UpdateConfig as well
+			newConfig := &HitlessUpgradeConfig{
+				Enabled:           !tt.expectedConfig.Enabled,
+				TransitionTimeout: 0, // Zero value should use default
+				CleanupInterval:   0, // Zero value should use default
+			}
+
+			err := integration.UpdateConfig(newConfig)
+			if err != nil {
+				t.Fatalf("Failed to update config: %v", err)
+			}
+
+			// Verify updated config has defaults applied
+			updatedConfig := integration.GetConfig()
+			if updatedConfig.Enabled == tt.expectedConfig.Enabled {
+				t.Error("Enabled should have been toggled")
+			}
+			if updatedConfig.TransitionTimeout != 60*time.Second {
+				t.Errorf("TransitionTimeout should use default (60s), got %v", updatedConfig.TransitionTimeout)
+			}
+			if updatedConfig.CleanupInterval != 30*time.Second {
+				t.Errorf("CleanupInterval should use default (30s), got %v", updatedConfig.CleanupInterval)
+			}
+		})
+	}
+}
+
+func TestDefaultHitlessUpgradeConfig(t *testing.T) {
+	config := DefaultHitlessUpgradeConfig()
+	
+	if config == nil {
+		t.Fatal("Default config should not be nil")
+	}
+	
+	if !config.Enabled {
+		t.Error("Default config should have Enabled=true")
+	}
+	
+	if config.TransitionTimeout != 60*time.Second {
+		t.Errorf("Default TransitionTimeout should be 60s, got %v", config.TransitionTimeout)
+	}
+	
+	if config.CleanupInterval != 30*time.Second {
+		t.Errorf("Default CleanupInterval should be 30s, got %v", config.CleanupInterval)
+	}
+}
+
+func TestHitlessUpgradeConfig_ZeroValueHandling(t *testing.T) {
+	// Test that zero values are properly handled in various scenarios
+	
+	// Test 1: Partial config with some zero values
+	partialConfig := &HitlessUpgradeConfig{
+		Enabled: true,
+		// TransitionTimeout and CleanupInterval are zero values
+	}
+	
+	integration := newHitlessIntegrationWithTimeouts(partialConfig, 3*time.Second, 3*time.Second)
+	if integration == nil {
+		t.Fatal("Integration should not be nil")
+	}
+	
+	config := integration.GetConfig()
+	if config.TransitionTimeout == 0 {
+		t.Error("Zero TransitionTimeout should have been replaced with default")
+	}
+	if config.CleanupInterval == 0 {
+		t.Error("Zero CleanupInterval should have been replaced with default")
+	}
+	
+	// Test 2: Empty struct
+	emptyConfig := &HitlessUpgradeConfig{}
+	
+	integration2 := newHitlessIntegrationWithTimeouts(emptyConfig, 3*time.Second, 3*time.Second)
+	if integration2 == nil {
+		t.Fatal("Integration should not be nil")
+	}
+	
+	config2 := integration2.GetConfig()
+	if config2.TransitionTimeout == 0 {
+		t.Error("Zero TransitionTimeout in empty config should have been replaced with default")
+	}
+	if config2.CleanupInterval == 0 {
+		t.Error("Zero CleanupInterval in empty config should have been replaced with default")
+	}
+}

internal/hitless/README.md

@@ -0,0 +1,23 @@
+# Hitless Upgrade Package
+
+This package implements hitless upgrade functionality for Redis cluster clients using the push notification architecture. It provides handlers for managing connection and pool state during Redis cluster upgrades.
+
+## Quick Start
+
+To enable hitless upgrades in your Redis client, simply set the configuration option:
+
+```go
+import "github.com/redis/go-redis/v9"
+
+// Enable hitless upgrades with a simple configuration option
+client := redis.NewClusterClient(&redis.ClusterOptions{
+    Addrs:           []string{"127.0.0.1:7000", "127.0.0.1:7001", "127.0.0.1:7002"},
+    Protocol:        3,    // RESP3 required for push notifications
+    HitlessUpgrades: true, // Enable hitless upgrades
+})
+defer client.Close()
+
+// That's it! Use your client normally - hitless upgrades work automatically
+ctx := context.Background()
+client.Set(ctx, "key", "value", 0)
+```

internal/hitless/client_integration.go

@@ -0,0 +1,200 @@
+package hitless
+
+import (
+	"context"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/redis/go-redis/v9/internal/pool"
+	"github.com/redis/go-redis/v9/push"
+)
+
+// ClientIntegrator provides integration between hitless upgrade handlers and Redis clients
+type ClientIntegrator struct {
+	upgradeHandler *UpgradeHandler
+	mu             sync.RWMutex
+
+	// Simple atomic state for pool redirection
+	isMoving    int32  // atomic: 0 = not moving, 1 = moving
+	newEndpoint string // only written during MOVING, read-only after
+}
+
+// NewClientIntegrator creates a new client integrator with client timeout configuration
+func NewClientIntegrator(defaultReadTimeout, defaultWriteTimeout time.Duration) *ClientIntegrator {
+	return &ClientIntegrator{
+		upgradeHandler: NewUpgradeHandler(defaultReadTimeout, defaultWriteTimeout),
+	}
+}
+
+// GetUpgradeHandler returns the upgrade handler for direct access
+func (ci *ClientIntegrator) GetUpgradeHandler() *UpgradeHandler {
+	return ci.upgradeHandler
+}
+
+// HandlePushNotification is the main entry point for processing upgrade notifications
+func (ci *ClientIntegrator) HandlePushNotification(ctx context.Context, handlerCtx push.NotificationHandlerContext, notification []interface{}) error {
+	// Handle MOVING notifications for pool redirection
+	if len(notification) > 0 {
+		if notificationType, ok := notification[0].(string); ok && notificationType == "MOVING" {
+			if len(notification) >= 3 {
+				if newEndpoint, ok := notification[2].(string); ok {
+					// Simple atomic state update - no locks needed
+					ci.newEndpoint = newEndpoint
+					atomic.StoreInt32(&ci.isMoving, 1)
+				}
+			}
+		}
+	}
+
+	return ci.upgradeHandler.HandlePushNotification(ctx, handlerCtx, notification)
+}
+
+// Close shuts down the client integrator
+func (ci *ClientIntegrator) Close() error {
+	ci.mu.Lock()
+	defer ci.mu.Unlock()
+
+	// Reset atomic state
+	atomic.StoreInt32(&ci.isMoving, 0)
+	ci.newEndpoint = ""
+
+	return nil
+}
+
+// IsMoving returns true if the pool is currently moving to a new endpoint
+// Uses atomic read - no locks needed
+func (ci *ClientIntegrator) IsMoving() bool {
+	return atomic.LoadInt32(&ci.isMoving) == 1
+}
+
+// GetNewEndpoint returns the new endpoint if moving, empty string otherwise
+// Safe to read without locks since it's only written during MOVING
+func (ci *ClientIntegrator) GetNewEndpoint() string {
+	if ci.IsMoving() {
+		return ci.newEndpoint
+	}
+	return ""
+}
+
+// PushNotificationHandlerInterface defines the interface for push notification handlers
+// This implements the interface expected by the push notification system
+type PushNotificationHandlerInterface interface {
+	HandlePushNotification(ctx context.Context, handlerCtx push.NotificationHandlerContext, notification []interface{}) error
+}
+
+// Ensure ClientIntegrator implements the interface
+var _ PushNotificationHandlerInterface = (*ClientIntegrator)(nil)
+
+// PoolRedirector provides pool redirection functionality for hitless upgrades
+type PoolRedirector struct {
+	poolManager *PoolEndpointManager
+	mu          sync.RWMutex
+}
+
+// NewPoolRedirector creates a new pool redirector
+func NewPoolRedirector() *PoolRedirector {
+	return &PoolRedirector{
+		poolManager: NewPoolEndpointManager(),
+	}
+}
+
+// RedirectPool redirects a connection pool to a new endpoint
+func (pr *PoolRedirector) RedirectPool(ctx context.Context, pooler pool.Pooler, newEndpoint string, timeout time.Duration) error {
+	pr.mu.Lock()
+	defer pr.mu.Unlock()
+
+	return pr.poolManager.RedirectPool(ctx, pooler, newEndpoint, timeout)
+}
+
+// IsPoolRedirected checks if a pool is currently redirected
+func (pr *PoolRedirector) IsPoolRedirected(pooler pool.Pooler) bool {
+	pr.mu.RLock()
+	defer pr.mu.RUnlock()
+
+	return pr.poolManager.IsPoolRedirected(pooler)
+}
+
+// GetRedirection returns redirection information for a pool
+func (pr *PoolRedirector) GetRedirection(pooler pool.Pooler) (*EndpointRedirection, bool) {
+	pr.mu.RLock()
+	defer pr.mu.RUnlock()
+
+	return pr.poolManager.GetRedirection(pooler)
+}
+
+// Close shuts down the pool redirector
+func (pr *PoolRedirector) Close() error {
+	pr.mu.Lock()
+	defer pr.mu.Unlock()
+
+	// Clean up all redirections
+	ctx := context.Background()
+	pr.poolManager.CleanupExpiredRedirections(ctx)
+
+	return nil
+}
+
+// ConnectionStateTracker tracks connection states during upgrades
+type ConnectionStateTracker struct {
+	upgradeHandler *UpgradeHandler
+	mu             sync.RWMutex
+}
+
+// NewConnectionStateTracker creates a new connection state tracker with timeout configuration
+func NewConnectionStateTracker(defaultReadTimeout, defaultWriteTimeout time.Duration) *ConnectionStateTracker {
+	return &ConnectionStateTracker{
+		upgradeHandler: NewUpgradeHandler(defaultReadTimeout, defaultWriteTimeout),
+	}
+}
+
+// IsConnectionTransitioning checks if a connection is currently transitioning
+func (cst *ConnectionStateTracker) IsConnectionTransitioning(conn *pool.Conn) bool {
+	cst.mu.RLock()
+	defer cst.mu.RUnlock()
+
+	return cst.upgradeHandler.IsConnectionTransitioning(conn)
+}
+
+// GetConnectionState returns the current state of a connection
+func (cst *ConnectionStateTracker) GetConnectionState(conn *pool.Conn) (*ConnectionState, bool) {
+	cst.mu.RLock()
+	defer cst.mu.RUnlock()
+
+	return cst.upgradeHandler.GetConnectionState(conn)
+}
+
+// CleanupConnection removes tracking for a connection
+func (cst *ConnectionStateTracker) CleanupConnection(conn *pool.Conn) {
+	cst.mu.Lock()
+	defer cst.mu.Unlock()
+
+	cst.upgradeHandler.CleanupConnection(conn)
+}
+
+// Close shuts down the connection state tracker
+func (cst *ConnectionStateTracker) Close() error {
+	cst.mu.Lock()
+	defer cst.mu.Unlock()
+
+	// Clean up all expired states
+	cst.upgradeHandler.CleanupExpiredStates()
+
+	return nil
+}
+
+// HitlessUpgradeConfig provides configuration for hitless upgrades
+type HitlessUpgradeConfig struct {
+	Enabled           bool
+	TransitionTimeout time.Duration
+	CleanupInterval   time.Duration
+}
+
+// DefaultHitlessUpgradeConfig returns default configuration for hitless upgrades
+func DefaultHitlessUpgradeConfig() *HitlessUpgradeConfig {
+	return &HitlessUpgradeConfig{
+		Enabled:           true,
+		TransitionTimeout: 60 * time.Second, // Longer timeout for transitioning connections
+		CleanupInterval:   30 * time.Second, // How often to clean up expired states
+	}
+}

internal/hitless/pool_manager.go

@@ -0,0 +1,205 @@
+package hitless
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"sync"
+	"time"
+
+	"github.com/redis/go-redis/v9/internal"
+	"github.com/redis/go-redis/v9/internal/pool"
+)
+
+// PoolEndpointManager manages endpoint transitions for connection pools during hitless upgrades.
+// It provides functionality to redirect new connections to new endpoints while maintaining
+// existing connections until they can be gracefully transitioned.
+type PoolEndpointManager struct {
+	mu sync.RWMutex
+
+	// Map of pools to their endpoint redirections
+	redirections map[interface{}]*EndpointRedirection
+
+	// Original dialers for pools (to restore after transition)
+	originalDialers map[interface{}]func(context.Context) (net.Conn, error)
+}
+
+// EndpointRedirection represents an active endpoint redirection
+type EndpointRedirection struct {
+	OriginalEndpoint string
+	NewEndpoint      string
+	StartTime        time.Time
+	Timeout          time.Duration
+
+	// Statistics
+	NewConnections    int64
+	FailedConnections int64
+}
+
+// NewPoolEndpointManager creates a new pool endpoint manager
+func NewPoolEndpointManager() *PoolEndpointManager {
+	return &PoolEndpointManager{
+		redirections:    make(map[interface{}]*EndpointRedirection),
+		originalDialers: make(map[interface{}]func(context.Context) (net.Conn, error)),
+	}
+}
+
+// RedirectPool redirects new connections from a pool to a new endpoint
+func (m *PoolEndpointManager) RedirectPool(ctx context.Context, pooler pool.Pooler, newEndpoint string, timeout time.Duration) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	// Check if pool is already being redirected
+	if _, exists := m.redirections[pooler]; exists {
+		return fmt.Errorf("pool is already being redirected")
+	}
+
+	// Get the current dialer from the pool
+	connPool, ok := pooler.(*pool.ConnPool)
+	if !ok {
+		return fmt.Errorf("unsupported pool type: %T", pooler)
+	}
+
+	// Store original dialer
+	originalDialer := m.getPoolDialer(connPool)
+	if originalDialer == nil {
+		return fmt.Errorf("could not get original dialer from pool")
+	}
+
+	m.originalDialers[pooler] = originalDialer
+
+	// Create new dialer that connects to the new endpoint
+	newDialer := m.createRedirectDialer(ctx, newEndpoint, originalDialer)
+
+	// Replace the pool's dialer
+	if err := m.setPoolDialer(connPool, newDialer); err != nil {
+		delete(m.originalDialers, pooler)
+		return fmt.Errorf("failed to set new dialer: %w", err)
+	}
+
+	// Record the redirection
+	m.redirections[pooler] = &EndpointRedirection{
+		OriginalEndpoint: m.extractEndpointFromDialer(originalDialer),
+		NewEndpoint:      newEndpoint,
+		StartTime:        time.Now(),
+		Timeout:          timeout,
+	}
+
+	internal.Logger.Printf(ctx, "hitless: redirected pool to new endpoint %s", newEndpoint)
+
+	return nil
+}
+
+// IsPoolRedirected checks if a pool is currently being redirected
+func (m *PoolEndpointManager) IsPoolRedirected(pooler pool.Pooler) bool {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	_, exists := m.redirections[pooler]
+	return exists
+}
+
+// GetRedirection returns redirection information for a pool
+func (m *PoolEndpointManager) GetRedirection(pooler pool.Pooler) (*EndpointRedirection, bool) {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	redirection, exists := m.redirections[pooler]
+	if !exists {
+		return nil, false
+	}
+
+	// Return a copy to avoid race conditions
+	redirectionCopy := *redirection
+	return &redirectionCopy, true
+}
+
+// CleanupExpiredRedirections removes expired redirections
+func (m *PoolEndpointManager) CleanupExpiredRedirections(ctx context.Context) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	now := time.Now()
+
+	for pooler, redirection := range m.redirections {
+		if now.Sub(redirection.StartTime) > redirection.Timeout {
+			// TODO: Here we should decide if we need to failback to the original dialer,
+			// i.e. if the new endpoint did not produce any active connections.
+			delete(m.redirections, pooler)
+			delete(m.originalDialers, pooler)
+			internal.Logger.Printf(ctx, "hitless: cleaned up expired redirection for pool")
+		}
+	}
+}
+
+// createRedirectDialer creates a dialer that connects to the new endpoint
+func (m *PoolEndpointManager) createRedirectDialer(ctx context.Context, newEndpoint string, originalDialer func(context.Context) (net.Conn, error)) func(context.Context) (net.Conn, error) {
+	return func(dialCtx context.Context) (net.Conn, error) {
+		// Try to connect to the new endpoint
+		conn, err := net.DialTimeout("tcp", newEndpoint, 10*time.Second)
+		if err != nil {
+			internal.Logger.Printf(ctx, "hitless: failed to connect to new endpoint %s: %v", newEndpoint, err)
+
+			// Fallback to original dialer
+			return originalDialer(dialCtx)
+		}
+
+		internal.Logger.Printf(ctx, "hitless: successfully connected to new endpoint %s", newEndpoint)
+		return conn, nil
+	}
+}
+
+// getPoolDialer extracts the dialer from a connection pool
+func (m *PoolEndpointManager) getPoolDialer(connPool *pool.ConnPool) func(context.Context) (net.Conn, error) {
+	return connPool.GetDialer()
+}
+
+// setPoolDialer sets a new dialer for a connection pool
+func (m *PoolEndpointManager) setPoolDialer(connPool *pool.ConnPool, dialer func(context.Context) (net.Conn, error)) error {
+	return connPool.SetDialer(dialer)
+}
+
+// extractEndpointFromDialer extracts the endpoint address from a dialer
+func (m *PoolEndpointManager) extractEndpointFromDialer(dialer func(context.Context) (net.Conn, error)) string {
+	// Try to extract endpoint by making a test connection
+	ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
+	defer cancel()
+
+	conn, err := dialer(ctx)
+	if err != nil {
+		return "unknown"
+	}
+	defer conn.Close()
+
+	if conn.RemoteAddr() != nil {
+		return conn.RemoteAddr().String()
+	}
+
+	return "unknown"
+}
+
+// GetActiveRedirections returns all active redirections
+func (m *PoolEndpointManager) GetActiveRedirections() map[interface{}]*EndpointRedirection {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	// Create copies to avoid race conditions
+	redirections := make(map[interface{}]*EndpointRedirection)
+	for pooler, redirection := range m.redirections {
+		redirectionCopy := *redirection
+		redirections[pooler] = &redirectionCopy
+	}
+
+	return redirections
+}
+
+// UpdateRedirectionStats updates statistics for a redirection
+func (m *PoolEndpointManager) UpdateRedirectionStats(pooler pool.Pooler, newConnections, failedConnections int64) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	if redirection, exists := m.redirections[pooler]; exists {
+		redirection.NewConnections += newConnections
+		redirection.FailedConnections += failedConnections
+	}
+}

internal/hitless/redis_integration.go

@@ -0,0 +1,309 @@
+package hitless
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/redis/go-redis/v9/internal"
+	"github.com/redis/go-redis/v9/internal/pool"
+	"github.com/redis/go-redis/v9/push"
+)
+
+// UpgradeStatus represents the current status of all upgrade operations
+type UpgradeStatus struct {
+	ConnectionStates map[*pool.Conn]*ConnectionState
+	IsMoving         bool
+	NewEndpoint      string
+	Timestamp        time.Time
+}
+
+// UpgradeStatistics provides statistics about upgrade operations
+type UpgradeStatistics struct {
+	ActiveConnections      int
+	IsMoving               bool
+	MigratingConnections   int
+	FailingOverConnections int
+	Timestamp              time.Time
+}
+
+// RedisClientIntegration provides complete hitless upgrade integration for Redis clients
+type RedisClientIntegration struct {
+	clientIntegrator       *ClientIntegrator
+	connectionStateTracker *ConnectionStateTracker
+	config                 *HitlessUpgradeConfig
+
+	mu      sync.RWMutex
+	enabled bool
+}
+
+// NewRedisClientIntegration creates a new Redis client integration for hitless upgrades
+// This is used internally by the main hitless.go package
+func NewRedisClientIntegration(config *HitlessUpgradeConfig, defaultReadTimeout, defaultWriteTimeout time.Duration) *RedisClientIntegration {
+	// Start with defaults
+	defaults := DefaultHitlessUpgradeConfig()
+
+	// If config is nil, use all defaults
+	if config == nil {
+		config = defaults
+	} else {
+		// Ensure all fields are set with defaults if they are zero values
+		if config.TransitionTimeout == 0 {
+			config = &HitlessUpgradeConfig{
+				Enabled:           config.Enabled,
+				TransitionTimeout: defaults.TransitionTimeout,
+				CleanupInterval:   config.CleanupInterval,
+			}
+		}
+		if config.CleanupInterval == 0 {
+			config = &HitlessUpgradeConfig{
+				Enabled:           config.Enabled,
+				TransitionTimeout: config.TransitionTimeout,
+				CleanupInterval:   defaults.CleanupInterval,
+			}
+		}
+	}
+
+	return &RedisClientIntegration{
+		clientIntegrator:       NewClientIntegrator(defaultReadTimeout, defaultWriteTimeout),
+		connectionStateTracker: NewConnectionStateTracker(defaultReadTimeout, defaultWriteTimeout),
+		config:                 config,
+		enabled:                config.Enabled,
+	}
+}
+
+// EnableHitlessUpgrades enables hitless upgrade functionality
+func (rci *RedisClientIntegration) EnableHitlessUpgrades() {
+	rci.mu.Lock()
+	defer rci.mu.Unlock()
+	rci.enabled = true
+}
+
+// DisableHitlessUpgrades disables hitless upgrade functionality
+func (rci *RedisClientIntegration) DisableHitlessUpgrades() {
+	rci.mu.Lock()
+	defer rci.mu.Unlock()
+	rci.enabled = false
+}
+
+// IsEnabled returns whether hitless upgrades are enabled
+func (rci *RedisClientIntegration) IsEnabled() bool {
+	rci.mu.RLock()
+	defer rci.mu.RUnlock()
+	return rci.enabled
+}
+
+// No client registration needed - each client has its own hitless integration instance
+
+// HandlePushNotification processes push notifications for hitless upgrades
+func (rci *RedisClientIntegration) HandlePushNotification(ctx context.Context, handlerCtx push.NotificationHandlerContext, notification []interface{}) error {
+	if !rci.IsEnabled() {
+		// If disabled, just log and return without processing
+		internal.Logger.Printf(ctx, "hitless: received notification but hitless upgrades are disabled")
+		return nil
+	}
+
+	return rci.clientIntegrator.HandlePushNotification(ctx, handlerCtx, notification)
+}
+
+// IsConnectionTransitioning checks if a connection is currently transitioning
+func (rci *RedisClientIntegration) IsConnectionTransitioning(conn *pool.Conn) bool {
+	if !rci.IsEnabled() {
+		return false
+	}
+
+	return rci.connectionStateTracker.IsConnectionTransitioning(conn)
+}
+
+// GetConnectionState returns the current state of a connection
+func (rci *RedisClientIntegration) GetConnectionState(conn *pool.Conn) (*ConnectionState, bool) {
+	if !rci.IsEnabled() {
+		return nil, false
+	}
+
+	return rci.connectionStateTracker.GetConnectionState(conn)
+}
+
+// GetUpgradeStatus returns comprehensive status of all ongoing upgrades
+func (rci *RedisClientIntegration) GetUpgradeStatus() *UpgradeStatus {
+	connStates := rci.clientIntegrator.GetUpgradeHandler().GetActiveTransitions()
+
+	return &UpgradeStatus{
+		ConnectionStates: connStates,
+		IsMoving:         rci.clientIntegrator.IsMoving(),
+		NewEndpoint:      rci.clientIntegrator.GetNewEndpoint(),
+		Timestamp:        time.Now(),
+	}
+}
+
+// GetUpgradeStatistics returns statistics about upgrade operations
+func (rci *RedisClientIntegration) GetUpgradeStatistics() *UpgradeStatistics {
+	connStates := rci.clientIntegrator.GetUpgradeHandler().GetActiveTransitions()
+
+	stats := &UpgradeStatistics{
+		ActiveConnections: len(connStates),
+		IsMoving:          rci.clientIntegrator.IsMoving(),
+		Timestamp:         time.Now(),
+	}
+
+	// Count by type
+	stats.MigratingConnections = 0
+	stats.FailingOverConnections = 0
+	for _, state := range connStates {
+		switch state.TransitionType {
+		case "MIGRATING":
+			stats.MigratingConnections++
+		case "FAILING_OVER":
+			stats.FailingOverConnections++
+		}
+	}
+
+	return stats
+}
+
+// GetConnectionTimeout returns the appropriate timeout for a connection
+// If the connection is transitioning (MIGRATING/FAILING_OVER), returns the longer TransitionTimeout
+// Otherwise returns the provided defaultTimeout
+func (rci *RedisClientIntegration) GetConnectionTimeout(conn *pool.Conn, defaultTimeout time.Duration) time.Duration {
+	if !rci.IsEnabled() {
+		return defaultTimeout
+	}
+
+	// Check if connection is transitioning
+	if rci.connectionStateTracker.IsConnectionTransitioning(conn) {
+		// Use longer timeout for transitioning connections
+		return rci.config.TransitionTimeout
+	}
+
+	return defaultTimeout
+}
+
+// GetConnectionTimeouts returns both read and write timeouts for a connection
+func (rci *RedisClientIntegration) GetConnectionTimeouts(conn *pool.Conn, defaultReadTimeout, defaultWriteTimeout time.Duration) (time.Duration, time.Duration) {
+	if !rci.IsEnabled() {
+		return defaultReadTimeout, defaultWriteTimeout
+	}
+
+	// Use the upgrade handler to get appropriate timeouts
+	upgradeHandler := rci.clientIntegrator.GetUpgradeHandler()
+	return upgradeHandler.GetConnectionTimeouts(conn, defaultReadTimeout, defaultWriteTimeout, rci.config.TransitionTimeout)
+}
+
+// MarkConnectionAsBlocking marks a connection as having blocking commands
+func (rci *RedisClientIntegration) MarkConnectionAsBlocking(conn *pool.Conn, isBlocking bool) {
+	if !rci.IsEnabled() {
+		return
+	}
+
+	// Use the upgrade handler to mark connection as blocking
+	upgradeHandler := rci.clientIntegrator.GetUpgradeHandler()
+	upgradeHandler.MarkConnectionAsBlocking(conn, isBlocking)
+}
+
+// IsConnectionMarkedForClosing checks if a connection should be closed
+func (rci *RedisClientIntegration) IsConnectionMarkedForClosing(conn *pool.Conn) bool {
+	if !rci.IsEnabled() {
+		return false
+	}
+
+	// Use the upgrade handler to check if connection is marked for closing
+	upgradeHandler := rci.clientIntegrator.GetUpgradeHandler()
+	return upgradeHandler.IsConnectionMarkedForClosing(conn)
+}
+
+// ShouldRedirectBlockingConnection checks if a blocking connection should be redirected
+func (rci *RedisClientIntegration) ShouldRedirectBlockingConnection(conn *pool.Conn) (bool, string) {
+	if !rci.IsEnabled() {
+		return false, ""
+	}
+
+	// Check client integrator's atomic state for pool-level redirection
+	if rci.clientIntegrator.IsMoving() {
+		return true, rci.clientIntegrator.GetNewEndpoint()
+	}
+
+	// Check specific connection state
+	upgradeHandler := rci.clientIntegrator.GetUpgradeHandler()
+	return upgradeHandler.ShouldRedirectBlockingConnection(conn, rci.clientIntegrator)
+}
+
+// CleanupConnection removes tracking for a connection (called when connection is closed)
+func (rci *RedisClientIntegration) CleanupConnection(conn *pool.Conn) {
+	if rci.IsEnabled() {
+		rci.connectionStateTracker.CleanupConnection(conn)
+	}
+}
+
+// CleanupPool removed - no pool state to clean up
+
+// Close shuts down the Redis client integration
+func (rci *RedisClientIntegration) Close() error {
+	rci.mu.Lock()
+	defer rci.mu.Unlock()
+
+	var firstErr error
+
+	// Close all components
+	if err := rci.clientIntegrator.Close(); err != nil && firstErr == nil {
+		firstErr = err
+	}
+
+	// poolRedirector removed in simplified implementation
+
+	if err := rci.connectionStateTracker.Close(); err != nil && firstErr == nil {
+		firstErr = err
+	}
+
+	rci.enabled = false
+
+	return firstErr
+}
+
+// GetConfig returns the current configuration
+func (rci *RedisClientIntegration) GetConfig() *HitlessUpgradeConfig {
+	rci.mu.RLock()
+	defer rci.mu.RUnlock()
+
+	// Return a copy to prevent modification
+	configCopy := *rci.config
+	return &configCopy
+}
+
+// UpdateConfig updates the configuration
+func (rci *RedisClientIntegration) UpdateConfig(config *HitlessUpgradeConfig) error {
+	if config == nil {
+		return fmt.Errorf("config cannot be nil")
+	}
+
+	rci.mu.Lock()
+	defer rci.mu.Unlock()
+
+	// Start with defaults for any zero values
+	defaults := DefaultHitlessUpgradeConfig()
+
+	// Ensure all fields are set with defaults if they are zero values
+	enabled := config.Enabled
+	transitionTimeout := config.TransitionTimeout
+	cleanupInterval := config.CleanupInterval
+
+	// Apply defaults for zero values
+	if transitionTimeout == 0 {
+		transitionTimeout = defaults.TransitionTimeout
+	}
+	if cleanupInterval == 0 {
+		cleanupInterval = defaults.CleanupInterval
+	}
+
+	// Create properly configured config
+	finalConfig := &HitlessUpgradeConfig{
+		Enabled:           enabled,
+		TransitionTimeout: transitionTimeout,
+		CleanupInterval:   cleanupInterval,
+	}
+
+	rci.config = finalConfig
+	rci.enabled = finalConfig.Enabled
+
+	return nil
+}

internal/hitless/upgrade_handler.go

@@ -0,0 +1,500 @@
+package hitless
+
+import (
+	"context"
+	"fmt"
+	"strconv"
+	"sync"
+	"time"
+
+	"github.com/redis/go-redis/v9/internal"
+	"github.com/redis/go-redis/v9/internal/pool"
+	"github.com/redis/go-redis/v9/push"
+)
+
+// UpgradeHandler handles hitless upgrade push notifications for Redis cluster upgrades.
+// It implements different strategies based on notification type:
+// - MOVING: Changes pool state to use new endpoint for future connections
+//   - mark existing connections for closing, handle pubsub to change underlying connection, change pool dialer with the new endpoint
+//
+// - MIGRATING/FAILING_OVER: Marks specific connection as in transition
+//   - relaxing timeouts
+//
+// - MIGRATED/FAILED_OVER: Clears transition state for specific connection
+//   - return to original timeouts
+type UpgradeHandler struct {
+	mu sync.RWMutex
+
+	// Connection-specific state for MIGRATING/FAILING_OVER notifications
+	connectionStates map[*pool.Conn]*ConnectionState
+
+	// Pool-level state removed - using atomic state in ClusterUpgradeManager instead
+
+	// Client configuration for getting default timeouts
+	defaultReadTimeout  time.Duration
+	defaultWriteTimeout time.Duration
+}
+
+// ConnectionState tracks the state of a specific connection during upgrades
+type ConnectionState struct {
+	IsTransitioning bool
+	TransitionType  string
+	StartTime       time.Time
+	ShardID         string
+	TimeoutSeconds  int
+
+	// Timeout management
+	OriginalReadTimeout  time.Duration // Original read timeout
+	OriginalWriteTimeout time.Duration // Original write timeout
+
+	// MOVING state specific
+	MarkedForClosing bool      // Connection should be closed after current commands
+	IsBlocking       bool      // Connection has blocking commands
+	NewEndpoint      string    // New endpoint for blocking commands
+	LastCommandTime  time.Time // When the last command was sent
+}
+
+// PoolState removed - using atomic state in ClusterUpgradeManager instead
+
+// NewUpgradeHandler creates a new hitless upgrade handler with client timeout configuration
+func NewUpgradeHandler(defaultReadTimeout, defaultWriteTimeout time.Duration) *UpgradeHandler {
+	return &UpgradeHandler{
+		connectionStates:    make(map[*pool.Conn]*ConnectionState),
+		defaultReadTimeout:  defaultReadTimeout,
+		defaultWriteTimeout: defaultWriteTimeout,
+	}
+}
+
+// GetConnectionTimeouts returns the appropriate read and write timeouts for a connection
+// If the connection is transitioning, returns increased timeouts
+func (h *UpgradeHandler) GetConnectionTimeouts(conn *pool.Conn, defaultReadTimeout, defaultWriteTimeout, transitionTimeout time.Duration) (time.Duration, time.Duration) {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+
+	state, exists := h.connectionStates[conn]
+	if !exists || !state.IsTransitioning {
+		return defaultReadTimeout, defaultWriteTimeout
+	}
+
+	// For transitioning connections (MIGRATING/FAILING_OVER), use longer timeouts
+	switch state.TransitionType {
+	case "MIGRATING", "FAILING_OVER":
+		return transitionTimeout, transitionTimeout
+	case "MOVING":
+		// For MOVING connections, use default timeouts but mark for special handling
+		return defaultReadTimeout, defaultWriteTimeout
+	default:
+		return defaultReadTimeout, defaultWriteTimeout
+	}
+}
+
+// MarkConnectionForClosing marks a connection to be closed after current commands complete
+func (h *UpgradeHandler) MarkConnectionForClosing(conn *pool.Conn, newEndpoint string) {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	state, exists := h.connectionStates[conn]
+	if !exists {
+		state = &ConnectionState{
+			IsTransitioning: true,
+			TransitionType:  "MOVING",
+			StartTime:       time.Now(),
+		}
+		h.connectionStates[conn] = state
+	}
+
+	state.MarkedForClosing = true
+	state.NewEndpoint = newEndpoint
+	state.LastCommandTime = time.Now()
+}
+
+// IsConnectionMarkedForClosing checks if a connection should be closed
+func (h *UpgradeHandler) IsConnectionMarkedForClosing(conn *pool.Conn) bool {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+
+	state, exists := h.connectionStates[conn]
+	return exists && state.MarkedForClosing
+}
+
+// MarkConnectionAsBlocking marks a connection as having blocking commands
+func (h *UpgradeHandler) MarkConnectionAsBlocking(conn *pool.Conn, isBlocking bool) {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	state, exists := h.connectionStates[conn]
+	if !exists {
+		state = &ConnectionState{
+			IsTransitioning: false,
+		}
+		h.connectionStates[conn] = state
+	}
+
+	state.IsBlocking = isBlocking
+}
+
+// ShouldRedirectBlockingConnection checks if a blocking connection should be redirected
+// Uses client integrator's atomic state for pool-level checks - minimal locking
+func (h *UpgradeHandler) ShouldRedirectBlockingConnection(conn *pool.Conn, clientIntegrator interface{}) (bool, string) {
+	if conn != nil {
+		// Check specific connection - need lock only for connection state
+		h.mu.RLock()
+		state, exists := h.connectionStates[conn]
+		h.mu.RUnlock()
+
+		if exists && state.IsBlocking && state.TransitionType == "MOVING" && state.NewEndpoint != "" {
+			return true, state.NewEndpoint
+		}
+	}
+
+	// Check client integrator's atomic state - no locks needed
+	if ci, ok := clientIntegrator.(*ClientIntegrator); ok && ci != nil && ci.IsMoving() {
+		return true, ci.GetNewEndpoint()
+	}
+
+	return false, ""
+}
+
+// ShouldRedirectNewBlockingConnection removed - functionality merged into ShouldRedirectBlockingConnection
+
+// HandlePushNotification processes hitless upgrade push notifications
+func (h *UpgradeHandler) HandlePushNotification(ctx context.Context, handlerCtx push.NotificationHandlerContext, notification []interface{}) error {
+	if len(notification) == 0 {
+		return fmt.Errorf("hitless: empty notification received")
+	}
+
+	notificationType, ok := notification[0].(string)
+	if !ok {
+		return fmt.Errorf("hitless: notification type is not a string: %T", notification[0])
+	}
+
+	internal.Logger.Printf(ctx, "hitless: processing %s notification with %d elements", notificationType, len(notification))
+
+	switch notificationType {
+	case "MOVING":
+		return h.handleMovingNotification(ctx, handlerCtx, notification)
+	case "MIGRATING":
+		return h.handleMigratingNotification(ctx, handlerCtx, notification)
+	case "MIGRATED":
+		return h.handleMigratedNotification(ctx, handlerCtx, notification)
+	case "FAILING_OVER":
+		return h.handleFailingOverNotification(ctx, handlerCtx, notification)
+	case "FAILED_OVER":
+		return h.handleFailedOverNotification(ctx, handlerCtx, notification)
+	default:
+		internal.Logger.Printf(ctx, "hitless: unknown notification type: %s", notificationType)
+		return nil
+	}
+}
+
+// handleMovingNotification processes MOVING notifications that affect the entire pool
+// Format: ["MOVING", time_seconds, "new_endpoint"]
+func (h *UpgradeHandler) handleMovingNotification(ctx context.Context, handlerCtx push.NotificationHandlerContext, notification []interface{}) error {
+	if len(notification) < 3 {
+		return fmt.Errorf("hitless: MOVING notification requires at least 3 elements, got %d", len(notification))
+	}
+
+	// Parse timeout
+	timeoutSeconds, err := h.parseTimeoutSeconds(notification[1])
+	if err != nil {
+		return fmt.Errorf("hitless: failed to parse timeout for MOVING notification: %w", err)
+	}
+
+	// Parse new endpoint
+	newEndpoint, ok := notification[2].(string)
+	if !ok {
+		return fmt.Errorf("hitless: new endpoint is not a string: %T", notification[2])
+	}
+
+	internal.Logger.Printf(ctx, "hitless: MOVING notification - endpoint will move to %s in %d seconds", newEndpoint, timeoutSeconds)
+	h.mu.Lock()
+	// Mark all existing connections for closing after current commands complete
+	for _, state := range h.connectionStates {
+		state.MarkedForClosing = true
+		state.NewEndpoint = newEndpoint
+		state.TransitionType = "MOVING"
+		state.LastCommandTime = time.Now()
+	}
+	h.mu.Unlock()
+
+	internal.Logger.Printf(ctx, "hitless: marked existing connections for closing, new blocking commands will use %s", newEndpoint)
+
+	return nil
+}
+
+// Removed complex helper methods - simplified to direct inline logic
+
+// handleMigratingNotification processes MIGRATING notifications for specific connections
+// Format: ["MIGRATING", time_seconds, shard_id]
+func (h *UpgradeHandler) handleMigratingNotification(ctx context.Context, handlerCtx push.NotificationHandlerContext, notification []interface{}) error {
+	if len(notification) < 3 {
+		return fmt.Errorf("hitless: MIGRATING notification requires at least 3 elements, got %d", len(notification))
+	}
+
+	timeoutSeconds, err := h.parseTimeoutSeconds(notification[1])
+	if err != nil {
+		return fmt.Errorf("hitless: failed to parse timeout for MIGRATING notification: %w", err)
+	}
+
+	shardID, err := h.parseShardID(notification[2])
+	if err != nil {
+		return fmt.Errorf("hitless: failed to parse shard ID for MIGRATING notification: %w", err)
+	}
+
+	conn := handlerCtx.Conn
+	if conn == nil {
+		return fmt.Errorf("hitless: no connection available in handler context")
+	}
+
+	internal.Logger.Printf(ctx, "hitless: MIGRATING notification - shard %s will migrate in %d seconds on connection %p", shardID, timeoutSeconds, conn)
+
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	// Store original timeouts if not already stored
+	var originalReadTimeout, originalWriteTimeout time.Duration
+	if existingState, exists := h.connectionStates[conn]; exists {
+		originalReadTimeout = existingState.OriginalReadTimeout
+		originalWriteTimeout = existingState.OriginalWriteTimeout
+	} else {
+		// Get default timeouts from client configuration
+		originalReadTimeout = h.defaultReadTimeout
+		originalWriteTimeout = h.defaultWriteTimeout
+	}
+
+	h.connectionStates[conn] = &ConnectionState{
+		IsTransitioning:      true,
+		TransitionType:       "MIGRATING",
+		StartTime:            time.Now(),
+		ShardID:              shardID,
+		TimeoutSeconds:       timeoutSeconds,
+		OriginalReadTimeout:  originalReadTimeout,
+		OriginalWriteTimeout: originalWriteTimeout,
+		LastCommandTime:      time.Now(),
+	}
+
+	internal.Logger.Printf(ctx, "hitless: connection %p marked as MIGRATING with increased timeouts", conn)
+
+	return nil
+}
+
+// handleMigratedNotification processes MIGRATED notifications for specific connections
+// Format: ["MIGRATED", shard_id]
+func (h *UpgradeHandler) handleMigratedNotification(ctx context.Context, handlerCtx push.NotificationHandlerContext, notification []interface{}) error {
+	if len(notification) < 2 {
+		return fmt.Errorf("hitless: MIGRATED notification requires at least 2 elements, got %d", len(notification))
+	}
+
+	shardID, err := h.parseShardID(notification[1])
+	if err != nil {
+		return fmt.Errorf("hitless: failed to parse shard ID for MIGRATED notification: %w", err)
+	}
+
+	conn := handlerCtx.Conn
+	if conn == nil {
+		return fmt.Errorf("hitless: no connection available in handler context")
+	}
+
+	internal.Logger.Printf(ctx, "hitless: MIGRATED notification - shard %s migration completed on connection %p", shardID, conn)
+
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	// Clear the transitioning state for this connection and restore original timeouts
+	if state, exists := h.connectionStates[conn]; exists && state.TransitionType == "MIGRATING" && state.ShardID == shardID {
+		internal.Logger.Printf(ctx, "hitless: restoring original timeouts for connection %p (read: %v, write: %v)",
+			conn, state.OriginalReadTimeout, state.OriginalWriteTimeout)
+
+		// In a real implementation, this would restore the connection's original timeouts
+		// For now, we'll just log and delete the state
+		delete(h.connectionStates, conn)
+		internal.Logger.Printf(ctx, "hitless: cleared MIGRATING state and restored timeouts for connection %p", conn)
+	}
+
+	return nil
+}
+
+// handleFailingOverNotification processes FAILING_OVER notifications for specific connections
+// Format: ["FAILING_OVER", time_seconds, shard_id]
+func (h *UpgradeHandler) handleFailingOverNotification(ctx context.Context, handlerCtx push.NotificationHandlerContext, notification []interface{}) error {
+	if len(notification) < 3 {
+		return fmt.Errorf("hitless: FAILING_OVER notification requires at least 3 elements, got %d", len(notification))
+	}
+
+	timeoutSeconds, err := h.parseTimeoutSeconds(notification[1])
+	if err != nil {
+		return fmt.Errorf("hitless: failed to parse timeout for FAILING_OVER notification: %w", err)
+	}
+
+	shardID, err := h.parseShardID(notification[2])
+	if err != nil {
+		return fmt.Errorf("hitless: failed to parse shard ID for FAILING_OVER notification: %w", err)
+	}
+
+	conn := handlerCtx.Conn
+	if conn == nil {
+		return fmt.Errorf("hitless: no connection available in handler context")
+	}
+
+	internal.Logger.Printf(ctx, "hitless: FAILING_OVER notification - shard %s will failover in %d seconds on connection %p", shardID, timeoutSeconds, conn)
+
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	// Store original timeouts if not already stored
+	var originalReadTimeout, originalWriteTimeout time.Duration
+	if existingState, exists := h.connectionStates[conn]; exists {
+		originalReadTimeout = existingState.OriginalReadTimeout
+		originalWriteTimeout = existingState.OriginalWriteTimeout
+	} else {
+		// Get default timeouts from client configuration
+		originalReadTimeout = h.defaultReadTimeout
+		originalWriteTimeout = h.defaultWriteTimeout
+	}
+
+	h.connectionStates[conn] = &ConnectionState{
+		IsTransitioning:      true,
+		TransitionType:       "FAILING_OVER",
+		StartTime:            time.Now(),
+		ShardID:              shardID,
+		TimeoutSeconds:       timeoutSeconds,
+		OriginalReadTimeout:  originalReadTimeout,
+		OriginalWriteTimeout: originalWriteTimeout,
+		LastCommandTime:      time.Now(),
+	}
+
+	internal.Logger.Printf(ctx, "hitless: connection %p marked as FAILING_OVER with increased timeouts", conn)
+
+	return nil
+}
+
+// handleFailedOverNotification processes FAILED_OVER notifications for specific connections
+// Format: ["FAILED_OVER", shard_id]
+func (h *UpgradeHandler) handleFailedOverNotification(ctx context.Context, handlerCtx push.NotificationHandlerContext, notification []interface{}) error {
+	if len(notification) < 2 {
+		return fmt.Errorf("hitless: FAILED_OVER notification requires at least 2 elements, got %d", len(notification))
+	}
+
+	shardID, err := h.parseShardID(notification[1])
+	if err != nil {
+		return fmt.Errorf("hitless: failed to parse shard ID for FAILED_OVER notification: %w", err)
+	}
+
+	conn := handlerCtx.Conn
+	if conn == nil {
+		return fmt.Errorf("hitless: no connection available in handler context")
+	}
+
+	internal.Logger.Printf(ctx, "hitless: FAILED_OVER notification - shard %s failover completed on connection %p", shardID, conn)
+
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	// Clear the transitioning state for this connection and restore original timeouts
+	if state, exists := h.connectionStates[conn]; exists && state.TransitionType == "FAILING_OVER" && state.ShardID == shardID {
+		internal.Logger.Printf(ctx, "hitless: restoring original timeouts for connection %p (read: %v, write: %v)",
+			conn, state.OriginalReadTimeout, state.OriginalWriteTimeout)
+
+		// In a real implementation, this would restore the connection's original timeouts
+		// For now, we'll just log and delete the state
+		delete(h.connectionStates, conn)
+		internal.Logger.Printf(ctx, "hitless: cleared FAILING_OVER state and restored timeouts for connection %p", conn)
+	}
+
+	return nil
+}
+
+// parseTimeoutSeconds parses timeout value from notification
+func (h *UpgradeHandler) parseTimeoutSeconds(value interface{}) (int, error) {
+	switch v := value.(type) {
+	case int64:
+		return int(v), nil
+	case int:
+		return v, nil
+	case string:
+		return strconv.Atoi(v)
+	default:
+		return 0, fmt.Errorf("unsupported timeout type: %T", value)
+	}
+}
+
+// parseShardID parses shard ID from notification
+func (h *UpgradeHandler) parseShardID(value interface{}) (string, error) {
+	switch v := value.(type) {
+	case string:
+		return v, nil
+	case int64:
+		return strconv.FormatInt(v, 10), nil
+	case int:
+		return strconv.Itoa(v), nil
+	default:
+		return "", fmt.Errorf("unsupported shard ID type: %T", value)
+	}
+}
+
+// GetConnectionState returns the current state of a connection
+func (h *UpgradeHandler) GetConnectionState(conn *pool.Conn) (*ConnectionState, bool) {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+
+	state, exists := h.connectionStates[conn]
+	if !exists {
+		return nil, false
+	}
+
+	// Return a copy to avoid race conditions
+	stateCopy := *state
+	return &stateCopy, true
+}
+
+// IsConnectionTransitioning checks if a connection is currently transitioning
+func (h *UpgradeHandler) IsConnectionTransitioning(conn *pool.Conn) bool {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+
+	state, exists := h.connectionStates[conn]
+	return exists && state.IsTransitioning
+}
+
+// IsPoolMoving and GetNewEndpoint removed - using atomic state in ClusterUpgradeManager instead
+
+// CleanupExpiredStates removes expired connection and pool states
+func (h *UpgradeHandler) CleanupExpiredStates() {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	now := time.Now()
+
+	// Cleanup expired connection states
+	for conn, state := range h.connectionStates {
+		timeout := time.Duration(state.TimeoutSeconds) * time.Second
+		if now.Sub(state.StartTime) > timeout {
+			delete(h.connectionStates, conn)
+		}
+	}
+
+	// Pool state cleanup removed - using atomic state in ClusterUpgradeManager instead
+}
+
+// CleanupConnection removes state for a specific connection (called when connection is closed)
+func (h *UpgradeHandler) CleanupConnection(conn *pool.Conn) {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	delete(h.connectionStates, conn)
+}
+
+// GetActiveTransitions returns information about all active connection transitions
+func (h *UpgradeHandler) GetActiveTransitions() map[*pool.Conn]*ConnectionState {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+
+	// Create copies to avoid race conditions
+	connStates := make(map[*pool.Conn]*ConnectionState)
+	for conn, state := range h.connectionStates {
+		stateCopy := *state
+		connStates[conn] = &stateCopy
+	}
+
+	return connStates
+}

internal/pool/pool.go

@@ -565,3 +565,24 @@ func (p *ConnPool) isHealthyConn(cn *Conn) bool {
 	cn.SetUsedAt(now)
 	return true
 }
+
+// GetDialer returns the current dialer function for the pool
+func (p *ConnPool) GetDialer() func(context.Context) (net.Conn, error) {
+	p.connsMu.Lock()
+	defer p.connsMu.Unlock()
+	return p.cfg.Dialer
+}
+
+// SetDialer sets a new dialer function for the pool
+// This is used for hitless upgrades to redirect new connections to new endpoints
+func (p *ConnPool) SetDialer(dialer func(context.Context) (net.Conn, error)) error {
+	if p.closed() {
+		return ErrClosed
+	}
+
+	p.connsMu.Lock()
+	defer p.connsMu.Unlock()
+
+	p.cfg.Dialer = dialer
+	return nil
+}

internal/proto/peek_push_notification_test.go

@@ -3,6 +3,7 @@ package proto
 import (
 	"bytes"
 	"fmt"
+	"math/rand"
 	"strings"
 	"testing"
 )
@@ -215,9 +216,9 @@ func TestPeekPushNotificationName(t *testing.T) {
 					// This is acceptable behavior for malformed input
 					name, err := reader.PeekPushNotificationName()
 					if err != nil {
-						t.Logf("PeekPushNotificationName errored for corrupted data %s: %v", tc.name, err)
+						t.Logf("PeekPushNotificationName errored for corrupted data %s: %v (DATA: %s)", tc.name, err, tc.data)
 					} else {
-						t.Logf("PeekPushNotificationName returned '%s' for corrupted data %s", name, tc.name)
+						t.Logf("PeekPushNotificationName returned '%s' for corrupted data NAME: %s, DATA: %s", name, tc.name, tc.data)
 					}
 				})
 			}
@@ -293,15 +294,27 @@ func TestPeekPushNotificationName(t *testing.T) {
 func createValidPushNotification(notificationName, data string) *bytes.Buffer {
 	buf := &bytes.Buffer{}
 
+	simpleOrString := rand.Intn(2) == 0
+
 	if data == "" {
+
 		// Single element notification
 		buf.WriteString(">1\r\n")
+		if simpleOrString {
+			buf.WriteString(fmt.Sprintf("+%s\r\n", notificationName))
+		} else {
 			buf.WriteString(fmt.Sprintf("$%d\r\n%s\r\n", len(notificationName), notificationName))
+		}
 	} else {
 		// Two element notification
 		buf.WriteString(">2\r\n")
+		if simpleOrString {
+			buf.WriteString(fmt.Sprintf("+%s\r\n", notificationName))
+			buf.WriteString(fmt.Sprintf("+%s\r\n", data))
+		} else {
 			buf.WriteString(fmt.Sprintf("$%d\r\n%s\r\n", len(notificationName), notificationName))
-		buf.WriteString(fmt.Sprintf("$%d\r\n%s\r\n", len(data), data))
+			buf.WriteString(fmt.Sprintf("$%d\r\n%s\r\n", len(notificationName), notificationName))
+		}
 	}
 
 	return buf

internal/proto/reader.go

@@ -116,26 +116,55 @@ func (r *Reader) PeekPushNotificationName() (string, error) {
 	if buf[0] != RespPush {
 		return "", fmt.Errorf("redis: can't parse push notification: %q", buf)
 	}
-	// remove push notification type and length
-	buf = buf[2:]
+
+	if len(buf) < 3 {
+		return "", fmt.Errorf("redis: can't parse push notification: %q", buf)
+	}
+
+	// remove push notification type
+	buf = buf[1:]
+	// remove first line - e.g. >2\r\n
 	for i := 0; i < len(buf)-1; i++ {
 		if buf[i] == '\r' && buf[i+1] == '\n' {
 			buf = buf[i+2:]
 			break
+		} else {
+			if buf[i] < '0' || buf[i] > '9' {
+				return "", fmt.Errorf("redis: can't parse push notification: %q", buf)
 			}
 		}
+	}
+	if len(buf) < 2 {
+		return "", fmt.Errorf("redis: can't parse push notification: %q", buf)
+	}
+	// next line should be $<length><string>\r\n or +<length><string>\r\n
 	// should have the type of the push notification name and it's length
-	if buf[0] != RespString {
+	if buf[0] != RespString && buf[0] != RespStatus {
+		return "", fmt.Errorf("redis: can't parse push notification name: %q", buf)
+	}
+	typeOfName := buf[0]
+	// remove the type of the push notification name
+	buf = buf[1:]
+	if typeOfName == RespString {
+		// remove the length of the string
+		if len(buf) < 2 {
 			return "", fmt.Errorf("redis: can't parse push notification name: %q", buf)
 		}
-	// skip the length of the string
 		for i := 0; i < len(buf)-1; i++ {
 			if buf[i] == '\r' && buf[i+1] == '\n' {
 				buf = buf[i+2:]
 				break
+			} else {
+				if buf[i] < '0' || buf[i] > '9' {
+					return "", fmt.Errorf("redis: can't parse push notification name: %q", buf)
+				}
+			}
 		}
 	}
 
+	if len(buf) < 2 {
+		return "", fmt.Errorf("redis: can't parse push notification name: %q", buf)
+	}
 	// keep only the notification name
 	for i := 0; i < len(buf)-1; i++ {
 		if buf[i] == '\r' && buf[i+1] == '\n' {
@@ -143,6 +172,7 @@ func (r *Reader) PeekPushNotificationName() (string, error) {
 			break
 		}
 	}
+
 	return util.BytesToString(buf), nil
 }
 

options.go

@@ -224,6 +224,18 @@ type Options struct {
 	// PushNotificationProcessor is the processor for handling push notifications.
 	// If nil, a default processor will be created for RESP3 connections.
 	PushNotificationProcessor push.NotificationProcessor
+
+	// HitlessUpgrades enables hitless upgrade functionality for cluster upgrades.
+	// Requires Protocol: 3 (RESP3) for push notifications.
+	// When enabled, the client will automatically handle cluster upgrade notifications
+	// and manage connection/pool state transitions seamlessly.
+	//
+	// default: false
+	HitlessUpgrades bool
+
+	// HitlessUpgradeConfig provides custom configuration for hitless upgrades.
+	// If nil, default configuration will be used when HitlessUpgrades is true.
+	HitlessUpgradeConfig *HitlessUpgradeConfig
 }
 
 func (opt *Options) init() {

osscluster.go

@@ -110,6 +110,18 @@ type ClusterOptions struct {
 
 	// UnstableResp3 enables Unstable mode for Redis Search module with RESP3.
 	UnstableResp3 bool
+
+	// HitlessUpgrades enables hitless upgrade functionality for cluster upgrades.
+	// Requires Protocol: 3 (RESP3) for push notifications.
+	// When enabled, the client will automatically handle cluster upgrade notifications
+	// and manage connection/pool state transitions seamlessly.
+	//
+	// default: false
+	HitlessUpgrades bool
+
+	// HitlessUpgradeConfig provides custom configuration for hitless upgrades.
+	// If nil, default configuration will be used when HitlessUpgrades is true.
+	HitlessUpgradeConfig *HitlessUpgradeConfig
 }
 
 func (opt *ClusterOptions) init() {
@@ -329,6 +341,8 @@ func (opt *ClusterOptions) clientOptions() *Options {
 		// situations in the options below will prevent that from happening.
 		readOnly:             opt.ReadOnly && opt.ClusterSlots == nil,
 		UnstableResp3:        opt.UnstableResp3,
+		HitlessUpgrades:      opt.HitlessUpgrades,
+		HitlessUpgradeConfig: opt.HitlessUpgradeConfig,
 	}
 }
 
@@ -943,6 +957,9 @@ type ClusterClient struct {
 	cmdsInfoCache *cmdsInfoCache
 	cmdable
 	hooksMixin
+
+	// hitlessIntegration provides hitless upgrade functionality
+	hitlessIntegration HitlessIntegration
 }
 
 // NewClusterClient returns a Redis Cluster client as described in
@@ -969,6 +986,22 @@ func NewClusterClient(opt *ClusterOptions) *ClusterClient {
 		txPipeline: c.processTxPipeline,
 	})
 
+	// Initialize hitless upgrades if enabled
+	if opt.HitlessUpgrades {
+		if opt.Protocol != 3 {
+			internal.Logger.Printf(context.Background(), "hitless: RESP3 protocol required for hitless upgrades, but Protocol is %d", opt.Protocol)
+		} else {
+			timeoutProvider := newOptionsTimeoutProvider(opt.ReadTimeout, opt.WriteTimeout)
+			integration, err := initializeHitlessIntegration(c, opt.HitlessUpgradeConfig, timeoutProvider)
+			if err != nil {
+				internal.Logger.Printf(context.Background(), "hitless: failed to initialize hitless upgrades: %v", err)
+			} else {
+				c.hitlessIntegration = integration
+				internal.Logger.Printf(context.Background(), "hitless: successfully initialized hitless upgrades for cluster client")
+			}
+		}
+	}
+
 	return c
 }
 
@@ -977,6 +1010,14 @@ func (c *ClusterClient) Options() *ClusterOptions {
 	return c.opt
 }
 
+// GetHitlessIntegration returns the hitless integration instance for monitoring and control.
+// Returns nil if hitless upgrades are not enabled.
+func (c *ClusterClient) GetHitlessIntegration() HitlessIntegration {
+	return c.hitlessIntegration
+}
+
+// getPushNotificationProcessor removed - not needed in simplified implementation
+
 // ReloadState reloads cluster state. If available it calls ClusterSlots func
 // to get cluster slots information.
 func (c *ClusterClient) ReloadState(ctx context.Context) {
@@ -988,6 +1029,13 @@ func (c *ClusterClient) ReloadState(ctx context.Context) {
 // It is rare to Close a ClusterClient, as the ClusterClient is meant
 // to be long-lived and shared between many goroutines.
 func (c *ClusterClient) Close() error {
+	// Close hitless integration first
+	if c.hitlessIntegration != nil {
+		if err := c.hitlessIntegration.Close(); err != nil {
+			internal.Logger.Printf(context.Background(), "hitless: error closing hitless integration: %v", err)
+		}
+	}
+
 	return c.nodes.Close()
 }
 

push/handler_context.go

@@ -13,9 +13,6 @@ type NotificationHandlerContext struct {
 	// circular dependencies. The developer is responsible for type assertion.
 	// It can be one of the following types:
 	// - *redis.baseClient
-	// - *redis.Client
-	// - *redis.ClusterClient
-	// - *redis.Conn
 	Client interface{}
 
 	// ConnPool is the connection pool from which the connection was obtained.
@@ -25,7 +22,7 @@ type NotificationHandlerContext struct {
 	// - *pool.ConnPool
 	// - *pool.SingleConnPool
 	// - *pool.StickyConnPool
-	ConnPool interface{}
+	ConnPool pool.Pooler
 
 	// PubSub is the PubSub instance that received the notification.
 	// It is interface to both allow for future expansion and to avoid

redis.go

@@ -2,6 +2,7 @@ package redis
 
 import (
 	"context"
+	"crypto/tls"
 	"errors"
 	"fmt"
 	"net"
@@ -211,6 +212,9 @@ type baseClient struct {
 
 	// Push notification processing
 	pushProcessor push.NotificationProcessor
+
+	// hitlessIntegration provides hitless upgrade functionality
+	hitlessIntegration HitlessIntegration
 }
 
 func (c *baseClient) clone() *baseClient {
@@ -466,8 +470,17 @@ func (c *baseClient) releaseConn(ctx context.Context, cn *pool.Conn, err error)
 			// Push notification processing errors shouldn't break normal Redis operations
 			internal.Logger.Printf(ctx, "push: error processing pending notifications before releasing connection: %v", err)
 		}
+
+		// Check if connection is marked for closing due to hitless upgrades
+		if c.hitlessIntegration != nil && c.hitlessIntegration.IsConnectionMarkedForClosing(cn) {
+			// Connection is marked for closing (e.g., during MOVING state)
+			// Remove it instead of putting it back in the pool
+			internal.Logger.Printf(ctx, "hitless: closing connection marked for closure during upgrade")
+			c.connPool.Remove(ctx, cn, nil)
+		} else {
 			c.connPool.Put(ctx, cn)
 		}
+	}
 }
 
 func (c *baseClient) withConn(
@@ -528,7 +541,33 @@ func (c *baseClient) _process(ctx context.Context, cmd Cmder, attempt int) (bool
 	}
 
 	retryTimeout := uint32(0)
-	if err := c.withConn(ctx, func(ctx context.Context, cn *pool.Conn) error {
+
+	// Check if this is a blocking command that needs redirection
+	isBlockingCommand := cmd.readTimeout() != nil
+	var redirectedConn *pool.Conn
+	var shouldRedirect bool
+	var newEndpoint string
+
+	if c.hitlessIntegration != nil && isBlockingCommand {
+		// For blocking commands, check if we need to redirect to a new endpoint
+		// This happens during MOVING state when the endpoint is changing
+		shouldRedirect, newEndpoint = c.hitlessIntegration.ShouldRedirectBlockingConnection(nil)
+		if shouldRedirect {
+			// Create a new connection to the new endpoint
+			var err error
+			redirectedConn, err = c.createConnectionToEndpoint(ctx, newEndpoint)
+			if err != nil {
+				internal.Logger.Printf(ctx, "hitless: failed to create redirected connection to %s: %v", newEndpoint, err)
+				// Fall back to normal connection if redirection fails
+				shouldRedirect = false
+			} else {
+				internal.Logger.Printf(ctx, "hitless: redirecting blocking command %s to new endpoint %s", cmd.Name(), newEndpoint)
+			}
+		}
+	}
+
+	// Use redirected connection if available, otherwise use normal connection
+	connFunc := func(ctx context.Context, cn *pool.Conn) error {
 		// Process any pending push notifications before executing the command
 		if err := c.processPushNotifications(ctx, cn); err != nil {
 			// Log the error but don't fail the command execution
@@ -536,7 +575,19 @@ func (c *baseClient) _process(ctx context.Context, cmd Cmder, attempt int) (bool
 			internal.Logger.Printf(ctx, "push: error processing pending notifications before command: %v", err)
 		}
 
-		if err := cn.WithWriter(c.context(ctx), c.opt.WriteTimeout, func(wr *proto.Writer) error {
+		// Mark connection as blocking if this is a blocking command
+		if c.hitlessIntegration != nil && isBlockingCommand {
+			c.hitlessIntegration.MarkConnectionAsBlocking(cn, true)
+			internal.Logger.Printf(ctx, "hitless: marked connection as blocking for command %s", cmd.Name())
+		}
+
+		// Get appropriate write timeout for this connection
+		writeTimeout := c.opt.WriteTimeout
+		if c.hitlessIntegration != nil {
+			_, writeTimeout = c.hitlessIntegration.GetConnectionTimeouts(cn, c.opt.ReadTimeout, c.opt.WriteTimeout)
+		}
+
+		if err := cn.WithWriter(c.context(ctx), writeTimeout, func(wr *proto.Writer) error {
 			return writeCmd(wr, cmd)
 		}); err != nil {
 			atomic.StoreUint32(&retryTimeout, 1)
@@ -547,7 +598,7 @@ func (c *baseClient) _process(ctx context.Context, cmd Cmder, attempt int) (bool
 		if c.opt.Protocol != 2 && c.assertUnstableCommand(cmd) {
 			readReplyFunc = cmd.readRawReply
 		}
-		if err := cn.WithReader(c.context(ctx), c.cmdTimeout(cmd), func(rd *proto.Reader) error {
+		if err := cn.WithReader(c.context(ctx), c.cmdTimeoutForConnection(cmd, cn), func(rd *proto.Reader) error {
 			// To be sure there are no buffered push notifications, we process them before reading the reply
 			if err := c.processPendingPushNotificationWithReader(ctx, cn, rd); err != nil {
 				// Log the error but don't fail the command execution
@@ -564,8 +615,31 @@ func (c *baseClient) _process(ctx context.Context, cmd Cmder, attempt int) (bool
 			return err
 		}
 
+		// Unmark connection as blocking after command completes
+		if c.hitlessIntegration != nil && isBlockingCommand {
+			c.hitlessIntegration.MarkConnectionAsBlocking(cn, false)
+			internal.Logger.Printf(ctx, "hitless: unmarked connection as blocking after command %s completed", cmd.Name())
+		}
+
 		return nil
-	}); err != nil {
+	}
+
+	// Execute the command with either redirected or normal connection
+	var err error
+	if shouldRedirect && redirectedConn != nil {
+		// Use the redirected connection for blocking command
+		err = connFunc(ctx, redirectedConn)
+		// Close the redirected connection after use
+		defer func() {
+			redirectedConn.Close()
+			internal.Logger.Printf(ctx, "hitless: closed redirected connection to %s after blocking command completed", newEndpoint)
+		}()
+	} else {
+		// Use normal connection pool
+		err = c.withConn(ctx, connFunc)
+	}
+
+	if err != nil {
 		retry := shouldRetry(err, atomic.LoadUint32(&retryTimeout) == 1)
 		return retry, err
 	}
@@ -588,6 +662,70 @@ func (c *baseClient) cmdTimeout(cmd Cmder) time.Duration {
 	return c.opt.ReadTimeout
 }
 
+// cmdTimeoutForConnection returns the appropriate read timeout for a specific connection
+// taking into account hitless upgrade state
+func (c *baseClient) cmdTimeoutForConnection(cmd Cmder, cn *pool.Conn) time.Duration {
+	baseTimeout := c.cmdTimeout(cmd)
+
+	// If hitless upgrades are enabled, get dynamic timeout based on connection state
+	if c.hitlessIntegration != nil {
+		// For blocking commands, use the command's timeout but check if connection needs increased timeout
+		if cmd.readTimeout() != nil {
+			// For blocking commands, use the base timeout but apply hitless upgrade adjustments
+			adjustedTimeout := c.hitlessIntegration.GetConnectionTimeout(cn, baseTimeout)
+			return adjustedTimeout
+		} else {
+			// For regular commands, get both read and write timeouts (use read timeout for command)
+			readTimeout, _ := c.hitlessIntegration.GetConnectionTimeouts(cn, c.opt.ReadTimeout, c.opt.WriteTimeout)
+			return readTimeout
+		}
+	}
+
+	return baseTimeout
+}
+
+// createConnectionToEndpoint creates a new connection to a specific endpoint
+// This is used for redirecting blocking commands during MOVING state
+func (c *baseClient) createConnectionToEndpoint(ctx context.Context, endpoint string) (*pool.Conn, error) {
+	// Parse the endpoint to get host and port
+	addr := endpoint
+	if addr == "" {
+		return nil, fmt.Errorf("empty endpoint provided")
+	}
+
+	// Create a temporary dialer for the new endpoint
+	dialer := func(ctx context.Context) (net.Conn, error) {
+		netDialer := &net.Dialer{
+			Timeout:   c.opt.DialTimeout,
+			KeepAlive: 30 * time.Second,
+		}
+
+		if c.opt.TLSConfig == nil {
+			return netDialer.DialContext(ctx, c.opt.Network, addr)
+		}
+
+		return tls.DialWithDialer(netDialer, c.opt.Network, addr, c.opt.TLSConfig)
+	}
+
+	// Create a new connection using the dialer
+	netConn, err := dialer(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("failed to dial new endpoint %s: %w", endpoint, err)
+	}
+
+	// Wrap in pool.Conn
+	cn := pool.NewConn(netConn)
+
+	// Initialize the connection (auth, select db, etc.)
+	if err := c.initConn(ctx, cn); err != nil {
+		cn.Close()
+		return nil, fmt.Errorf("failed to initialize connection to %s: %w", endpoint, err)
+	}
+
+	internal.Logger.Printf(ctx, "hitless: created new connection to endpoint %s for blocking command redirection", endpoint)
+	return cn, nil
+}
+
 // context returns the context for the current connection.
 // If the context timeout is enabled, it returns the original context.
 // Otherwise, it returns a new background context.
@@ -604,8 +742,19 @@ func (c *baseClient) context(ctx context.Context) context.Context {
 // long-lived and shared between many goroutines.
 func (c *baseClient) Close() error {
 	var firstErr error
+
+	// Close hitless integration first
+	if c.hitlessIntegration != nil {
+		if err := c.hitlessIntegration.Close(); err != nil {
+			internal.Logger.Printf(context.Background(), "hitless: error closing hitless integration: %v", err)
+			if firstErr == nil {
+				firstErr = err
+			}
+		}
+	}
+
 	if c.onClose != nil {
-		if err := c.onClose(); err != nil {
+		if err := c.onClose(); err != nil && firstErr == nil {
 			firstErr = err
 		}
 	}
@@ -678,14 +827,15 @@ func (c *baseClient) pipelineProcessCmds(
 		internal.Logger.Printf(ctx, "push: error processing pending notifications before pipeline: %v", err)
 	}
 
-	if err := cn.WithWriter(c.context(ctx), c.opt.WriteTimeout, func(wr *proto.Writer) error {
+	readTimeout, writeTimeout := c.hitlessIntegration.GetConnectionTimeouts(cn, c.opt.ReadTimeout, c.opt.WriteTimeout)
+	if err := cn.WithWriter(c.context(ctx), writeTimeout, func(wr *proto.Writer) error {
 		return writeCmds(wr, cmds)
 	}); err != nil {
 		setCmdsErr(cmds, err)
 		return true, err
 	}
 
-	if err := cn.WithReader(c.context(ctx), c.opt.ReadTimeout, func(rd *proto.Reader) error {
+	if err := cn.WithReader(c.context(ctx), readTimeout, func(rd *proto.Reader) error {
 		// read all replies
 		return c.pipelineReadCmds(ctx, cn, rd, cmds)
 	}); err != nil {
@@ -725,14 +875,15 @@ func (c *baseClient) txPipelineProcessCmds(
 		internal.Logger.Printf(ctx, "push: error processing pending notifications before transaction: %v", err)
 	}
 
-	if err := cn.WithWriter(c.context(ctx), c.opt.WriteTimeout, func(wr *proto.Writer) error {
+	readTimeout, writeTimeout := c.hitlessIntegration.GetConnectionTimeouts(cn, c.opt.ReadTimeout, c.opt.WriteTimeout)
+	if err := cn.WithWriter(c.context(ctx), writeTimeout, func(wr *proto.Writer) error {
 		return writeCmds(wr, cmds)
 	}); err != nil {
 		setCmdsErr(cmds, err)
 		return true, err
 	}
 
-	if err := cn.WithReader(c.context(ctx), c.opt.ReadTimeout, func(rd *proto.Reader) error {
+	if err := cn.WithReader(c.context(ctx), readTimeout, func(rd *proto.Reader) error {
 		statusCmd := cmds[0].(*StatusCmd)
 		// Trim multi and exec.
 		trimmedCmds := cmds[1 : len(cmds)-1]
@@ -837,6 +988,22 @@ func NewClient(opt *Options) *Client {
 
 	c.connPool = newConnPool(opt, c.dialHook)
 
+	// Initialize hitless upgrades if enabled
+	if opt.HitlessUpgrades {
+		if opt.Protocol != 3 {
+			internal.Logger.Printf(context.Background(), "hitless: RESP3 protocol required for hitless upgrades, but Protocol is %d", opt.Protocol)
+		} else {
+			timeoutProvider := newOptionsTimeoutProvider(opt.ReadTimeout, opt.WriteTimeout)
+			integration, err := initializeHitlessIntegration(&c, opt.HitlessUpgradeConfig, timeoutProvider)
+			if err != nil {
+				internal.Logger.Printf(context.Background(), "hitless: failed to initialize hitless upgrades: %v", err)
+			} else {
+				c.hitlessIntegration = integration
+				internal.Logger.Printf(context.Background(), "hitless: successfully initialized hitless upgrades for client")
+			}
+		}
+	}
+
 	return &c
 }
 
@@ -857,6 +1024,12 @@ func (c *Client) WithTimeout(timeout time.Duration) *Client {
 	return &clone
 }
 
+// GetHitlessIntegration returns the hitless integration instance for monitoring and control.
+// Returns nil if hitless upgrades are not enabled.
+func (c *Client) GetHitlessIntegration() HitlessIntegration {
+	return c.hitlessIntegration
+}
+
 func (c *Client) Conn() *Conn {
 	return newConn(c.opt, pool.NewStickyConnPool(c.connPool), &c.hooksMixin)
 }