Add redis support for distributed caching (#83)

* Add redis support for distributed caching

* Move towards the self-provided Redis connection pool and RESP protocol implementation.
Official redis client library won't work with yaegi.

* fixup! Move towards the self-provided Redis connection pool and RESP protocol implementation. Official redis client library won't work with yaegi.

* fixup! fixup! Move towards the self-provided Redis connection pool and RESP protocol implementation. Official redis client library won't work with yaegi.

* fixup! fixup! fixup! Move towards the self-provided Redis connection pool and RESP protocol implementation. Official redis client library won't work with yaegi.

* fixup! fixup! fixup! fixup! Move towards the self-provided Redis connection pool and RESP protocol implementation. Official redis client library won't work with yaegi.

* fixup! fixup! fixup! fixup! fixup! Move towards the self-provided Redis connection pool and RESP protocol implementation. Official redis client library won't work with yaegi.

* ... and another all nighter.

* fixup! ... and another all nighter.

* fixup! fixup! ... and another all nighter.

* fixup! fixup! fixup! ... and another all nighter.

* Resolve issue #85 by adding ability to set custom claims in JWT tokens

* Remove redundant validation in auth middleware ( issue #89 )

* Add ability to set cookie prefix for session cookies ( #87 )

* fixup! Add ability to set cookie prefix for session cookies ( #87 )

* Add ability to set cookie max age - issue #91

* Potential fix for code scanning alert no. 10: Size computation for allocation may overflow

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>

* fixup! Merge main into 0.8.0-redis: resolve conflicts

---------

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>

internal/cache/backends/redis_health.go

@@ -0,0 +1,176 @@
+package backends
+
+import (
+	"context"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+// HealthMonitor continuously monitors Redis connection health and triggers reconnections
+type HealthMonitor struct {
+	pool   *ConnectionPool
+	config *HealthMonitorConfig
+
+	// State
+	healthy       atomic.Bool
+	running       atomic.Bool
+	lastCheckTime atomic.Int64 // Unix timestamp
+
+	// Metrics
+	consecutiveFailures atomic.Int64
+	totalChecks         atomic.Int64
+	totalFailures       atomic.Int64
+
+	// Lifecycle
+	stopChan chan struct{}
+	wg       sync.WaitGroup
+}
+
+// HealthMonitorConfig configures the health monitor
+type HealthMonitorConfig struct {
+	CheckInterval      time.Duration // How often to check health
+	Timeout            time.Duration // Timeout for health check
+	UnhealthyThreshold int           // Consecutive failures before marking unhealthy
+	OnHealthChange     func(healthy bool)
+}
+
+// DefaultHealthMonitorConfig returns default health monitor configuration
+func DefaultHealthMonitorConfig() *HealthMonitorConfig {
+	return &HealthMonitorConfig{
+		CheckInterval:      5 * time.Second,
+		Timeout:            3 * time.Second,
+		UnhealthyThreshold: 3,
+	}
+}
+
+// NewHealthMonitor creates a new health monitor
+func NewHealthMonitor(pool *ConnectionPool, config *HealthMonitorConfig) *HealthMonitor {
+	if config == nil {
+		config = DefaultHealthMonitorConfig()
+	}
+
+	hm := &HealthMonitor{
+		pool:     pool,
+		config:   config,
+		stopChan: make(chan struct{}),
+	}
+
+	hm.healthy.Store(true) // Assume healthy initially
+	return hm
+}
+
+// Start begins health monitoring
+func (hm *HealthMonitor) Start() {
+	if hm.running.Swap(true) {
+		return // Already running
+	}
+
+	hm.wg.Add(1)
+	go hm.monitorLoop()
+}
+
+// Stop stops health monitoring
+func (hm *HealthMonitor) Stop() {
+	if !hm.running.Swap(false) {
+		return // Not running
+	}
+
+	close(hm.stopChan)
+	hm.wg.Wait()
+}
+
+// IsHealthy returns the current health status
+func (hm *HealthMonitor) IsHealthy() bool {
+	return hm.healthy.Load()
+}
+
+// GetStats returns health monitor statistics
+func (hm *HealthMonitor) GetStats() map[string]interface{} {
+	lastCheck := time.Unix(hm.lastCheckTime.Load(), 0)
+
+	return map[string]interface{}{
+		"healthy":              hm.healthy.Load(),
+		"consecutive_failures": hm.consecutiveFailures.Load(),
+		"total_checks":         hm.totalChecks.Load(),
+		"total_failures":       hm.totalFailures.Load(),
+		"last_check":           lastCheck,
+	}
+}
+
+// monitorLoop runs the health check loop
+func (hm *HealthMonitor) monitorLoop() {
+	defer hm.wg.Done()
+
+	ticker := time.NewTicker(hm.config.CheckInterval)
+	defer ticker.Stop()
+
+	// Perform initial check immediately
+	hm.performHealthCheck()
+
+	for {
+		select {
+		case <-hm.stopChan:
+			return
+		case <-ticker.C:
+			hm.performHealthCheck()
+		}
+	}
+}
+
+// performHealthCheck executes a health check
+func (hm *HealthMonitor) performHealthCheck() {
+	hm.totalChecks.Add(1)
+	hm.lastCheckTime.Store(time.Now().Unix())
+
+	ctx, cancel := context.WithTimeout(context.Background(), hm.config.Timeout)
+	defer cancel()
+
+	// Try to get a connection and ping Redis
+	conn, err := hm.pool.Get(ctx)
+	if err != nil {
+		hm.recordFailure()
+		return
+	}
+	defer hm.pool.Put(conn)
+
+	// Ping Redis
+	_, err = conn.Do("PING")
+	if err != nil {
+		hm.recordFailure()
+		return
+	}
+
+	// Success!
+	hm.recordSuccess()
+}
+
+// recordSuccess records a successful health check
+func (hm *HealthMonitor) recordSuccess() {
+	wasHealthy := hm.healthy.Load()
+	hm.consecutiveFailures.Store(0)
+	hm.healthy.Store(true)
+
+	// Trigger callback if health changed
+	if !wasHealthy && hm.config.OnHealthChange != nil {
+		hm.config.OnHealthChange(true)
+	}
+}
+
+// recordFailure records a failed health check
+func (hm *HealthMonitor) recordFailure() {
+	hm.totalFailures.Add(1)
+	failures := hm.consecutiveFailures.Add(1)
+
+	wasHealthy := hm.healthy.Load()
+
+	// Mark unhealthy if threshold exceeded
+	if failures >= int64(hm.config.UnhealthyThreshold) {
+		hm.healthy.Store(false)
+
+		// Trigger callback if health changed
+		if wasHealthy && hm.config.OnHealthChange != nil {
+			hm.config.OnHealthChange(false)
+		}
+	}
+}