add logs for listener.

pkg/postage/listener/listener.go

@@ -219,12 +219,15 @@ func (l *listener) Listen(from uint64, updater postage.EventUpdater) <-chan stru
 			l.metrics.BackendCalls.Inc()
 
 			events, err := l.ev.FilterLogs(ctx, l.filterQuery(big.NewInt(int64(from)), big.NewInt(int64(to))))
+			l.logger.Info("listener filter logs from ", from, "to ", to)
 			if err != nil {
+				l.logger.Errorf("filter logs failed, err=%s", err.Error())
 				l.metrics.BackendErrors.Inc()
 				return err
 			}
 
 			if err := updater.TransactionStart(); err != nil {
+				l.logger.Errorf("TransactionStart failed, err=%s", err.Error())
 				return err
 			}
 
@@ -232,9 +235,11 @@ func (l *listener) Listen(from uint64, updater postage.EventUpdater) <-chan stru
 				startEv := time.Now()
 				err = updater.UpdateBlockNumber(e.BlockNumber)
 				if err != nil {
+					l.logger.Errorf("UpdateBlockNumber failed, err=%s", err.Error())
 					return err
 				}
 				if err = l.processEvent(e, updater); err != nil {
+					l.logger.Errorf("processEvent failed, err=%s", err.Error())
 					return err
 				}
 				totalTimeMetric(l.metrics.EventProcessDuration, startEv)
@@ -246,6 +251,7 @@ func (l *listener) Listen(from uint64, updater postage.EventUpdater) <-chan stru
 			}
 
 			if err := updater.TransactionEnd(); err != nil {
+				l.logger.Errorf("TransactionEnd failed, err=%s", err.Error())
 				return err
 			}