changefeed(ticdc): fix barrier ts set incorrectly cause monitor becom…

…e year (#11560)

close #11553

cdc/owner/changefeed.go

@@ -927,8 +927,6 @@ func (c *changefeed) handleBarrier(ctx context.Context,
 	barrier *schedulepb.BarrierWithMinTs,
 ) error {
 	barrierTp, barrierTs := c.barriers.Min()
-	c.metricsChangefeedBarrierTsGauge.Set(float64(oracle.ExtractPhysical(barrierTs)))
-
 	// It means:
 	//   1. All data before the barrierTs was sent to downstream.
 	//   2. No more data after barrierTs was sent to downstream.
@@ -970,6 +968,8 @@ func (c *changefeed) handleBarrier(ctx context.Context,
 		barrier.MinTableBarrierTs = barrierTs
 	}
 
+	// MinTableBarrierTs is always the next barrier that blocking the global resolvedTs.
+	c.metricsChangefeedBarrierTsGauge.Set(float64(oracle.ExtractPhysical(barrier.MinTableBarrierTs)))
 	return nil
 }