feat: 新增缓存同步器

internal/syncer/cache_syncer.go

@@ -0,0 +1,155 @@
+package syncer
+
+import (
+	"fmt"
+	"sync"
+	"time"
+
+	"gpt-load/internal/store"
+
+	"github.com/sirupsen/logrus"
+)
+
+// LoaderFunc defines a generic function signature for loading data from the source of truth (e.g., database).
+type LoaderFunc[T any] func() (T, error)
+
+// CacheSyncer is a generic service that manages in-memory caching and cross-instance synchronization.
+type CacheSyncer[T any] struct {
+	mu          sync.RWMutex
+	cache       T
+	loader      LoaderFunc[T]
+	store       store.Store
+	channelName string
+	logger      *logrus.Entry
+	stopChan    chan struct{}
+	wg          sync.WaitGroup
+}
+
+// NewCacheSyncer creates and initializes a new CacheSyncer.
+func NewCacheSyncer[T any](
+	loader LoaderFunc[T],
+	store store.Store,
+	channelName string,
+	logger *logrus.Entry,
+) (*CacheSyncer[T], error) {
+	s := &CacheSyncer[T]{
+		loader:      loader,
+		store:       store,
+		channelName: channelName,
+		logger:      logger,
+		stopChan:    make(chan struct{}),
+	}
+
+	if err := s.reload(); err != nil {
+		return nil, fmt.Errorf("initial load for %s failed: %w", channelName, err)
+	}
+
+	s.wg.Add(1)
+	go s.listenForUpdates()
+
+	return s, nil
+}
+
+// Get safely returns the cached data.
+func (s *CacheSyncer[T]) Get() T {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	return s.cache
+}
+
+// Invalidate publishes a notification to all instances to reload their cache.
+func (s *CacheSyncer[T]) Invalidate() error {
+	s.logger.Debug("publishing invalidation notification")
+	s.reload()
+	return s.store.Publish(s.channelName, []byte("reload"))
+}
+
+// Stop gracefully shuts down the syncer's background goroutine.
+func (s *CacheSyncer[T]) Stop() {
+	s.logger.Debug("stopping cache syncer...")
+	close(s.stopChan)
+	s.wg.Wait()
+	s.logger.Info("cache syncer stopped.")
+}
+
+// reload fetches the latest data using the loader function and updates the cache.
+func (s *CacheSyncer[T]) reload() error {
+	s.logger.Debug("reloading cache...")
+	newData, err := s.loader()
+	if err != nil {
+		s.logger.Errorf("failed to reload cache: %v", err)
+		return err
+	}
+
+	s.mu.Lock()
+	s.cache = newData
+	s.mu.Unlock()
+
+	s.logger.Info("cache reloaded successfully")
+	return nil
+}
+
+// listenForUpdates runs in the background, listening for invalidation messages.
+func (s *CacheSyncer[T]) listenForUpdates() {
+	defer s.wg.Done()
+
+	for {
+		select {
+		case <-s.stopChan:
+			s.logger.Info("received stop signal, exiting listener loop.")
+			return
+		default:
+		}
+
+		if s.store == nil {
+			s.logger.Warn("store is not configured, stopping subscription listener.")
+			return
+		}
+
+		subscription, err := s.store.Subscribe(s.channelName)
+		if err != nil {
+			s.logger.Errorf("failed to subscribe, retrying in 5s: %v", err)
+			select {
+			case <-time.After(5 * time.Second):
+				continue
+			case <-s.stopChan:
+				return
+			}
+		}
+
+		s.logger.Debugf("subscribed to channel: %s", s.channelName)
+
+	subscriberLoop:
+		for {
+			select {
+			case msg, ok := <-subscription.Channel():
+				if !ok {
+					s.logger.Warn("subscription channel closed, attempting to re-subscribe...")
+					break subscriberLoop // This will lead to closing the current subscription and retrying.
+				}
+				s.logger.Debugf("received invalidation notification, payload: %s", string(msg.Payload))
+				if err := s.reload(); err != nil {
+					s.logger.Errorf("failed to reload cache after notification: %v", err)
+				}
+			case <-s.stopChan:
+				s.logger.Info("received stop signal, exiting subscriber loop.")
+				if err := subscription.Close(); err != nil {
+					s.logger.Errorf("failed to close subscription: %v", err)
+				}
+				return
+			}
+		}
+
+		// Before retrying, ensure the old subscription is closed.
+		if err := subscription.Close(); err != nil {
+			s.logger.Errorf("failed to close subscription before retrying: %v", err)
+		}
+
+		// Wait a moment before retrying to avoid tight loops on persistent errors.
+		select {
+		case <-time.After(2 * time.Second):
+		case <-s.stopChan:
+			return
+		}
+	}
+}