more customer

pkg/actor/simple_grain_pool.go

@@ -43,6 +43,9 @@ type GrainPoolConfig[V any] struct {
 	Hostname         string
 	Spawn            func(ctx context.Context, id uint64) (Grain[V], error)
 	SpawnHost        func(host string) (Host[V], error)
+	// Destroy is an optional cleanup hook called when a grain is evicted on TTL
+	// (e.g. to detach inventory subscriptions wired into its mutations). Leave
+	// nil when there is nothing to clean up — purge() skips a nil Destroy.
 	Destroy          func(grain Grain[V]) error
 	TTL              time.Duration
 	PoolSize         int
@@ -96,8 +99,10 @@ func (p *SimpleGrainPool[V]) purge() {
 	for id, grain := range p.grains {
 		if grain.GetLastAccess().Before(purgeLimit) {
 			purgedIds = append(purgedIds, id)
-			if err := p.destroy(grain); err != nil {
-				log.Printf("failed to destroy grain %d: %v", id, err)
+			if p.destroy != nil {
+				if err := p.destroy(grain); err != nil {
+					log.Printf("failed to destroy grain %d: %v", id, err)
+				}
 			}
 
 			delete(p.grains, id)