[#1238] engine: Add non-blocking send in the shard's notification channel

Signed-off-by: Anton Nikiforov <an.nikiforov@yadro.com>

internal/logs/logs.go

@@ -252,6 +252,7 @@ const (
 	ShardCantInitializeMetabaseMoveToADegradedreadonlyMode               = "can't initialize metabase, move to a degraded-read-only mode"
 	ShardStopEventListenerByClosedEventChannel                           = "stop event listener by closed `event` channel"
 	ShardStopEventListenerByClosedStopChannel                            = "stop event listener by closed `stop` channel"
+	ShardEventProcessingInProgress                                       = "event processing is in progress, skip the received"
 	ShardStopEventListenerByContext                                      = "stop event listener by context"
 	ShardCouldNotSubmitGCJobToWorkerPool                                 = "could not submit GC job to worker pool"
 	ShardGCIsStopped                                                     = "GC is stopped"

pkg/local_object_storage/engine/shards.go

@@ -340,6 +340,9 @@ func (e *StorageEngine) HandleNewEpoch(ctx context.Context, epoch uint64) {
 		case <-ctx.Done():
 			return
 		case sh.NotificationChannel() <- ev:
+		default:
+			e.log.Debug(logs.ShardEventProcessingInProgress,
+				zap.Uint64("epoch", epoch), zap.Stringer("shard", sh.ID()))
 		}
 	}
 }