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Signed-off-by: Priya Bibra <[email protected]>

go/vt/vtgate/vstream_manager.go

@@ -691,13 +691,19 @@ func (vs *vstream) streamFromTablet(ctx context.Context, sgtid *binlogdatapb.Sha
 	}
 }
 
+// isRetriable determines whether we should exit immediately or retry the vstream.
+// The first return value determines if the error is retriable, the second indicates whether
+// the tablet on which the error occurred should be ommitted from the candidate list of tablets
+// to choose from on the retry.
 func (vs *vstream) isRetriableError(err error) (bool, bool) {
 	errCode := vterrors.Code(err)
 
 	if errCode == vtrpcpb.Code_FAILED_PRECONDITION || errCode == vtrpcpb.Code_UNAVAILABLE {
 		return true, false
 	}
 
+	// If there is a GTIDSet Mismatch on the tablet or if the tablet cannot be found,
+	// omit it from the candidate list in the TabletPicker on retry.
 	if (errCode == vtrpcpb.Code_INVALID_ARGUMENT && strings.Contains(err.Error(), "GTIDSet Mismatch")) || errCode == vtrpcpb.Code_NOT_FOUND {
 		return true, true
 	}

go/vt/vtgate/vstream_manager_test.go

@@ -461,7 +461,7 @@ func TestVStreamRetriableErrors(t *testing.T) {
 
 			vsm := newTestVStreamManager(ctx, hc, st, cells[0])
 
-			// always have the local cell tablet error so it's ignored on retry and we pick the other one
+			// Always have the local cell tablet error so it's ignored on retry and we pick the other one
 			// if the error requires ignoring the tablet on retry
 			sbc0.AddVStreamEvents(nil, vterrors.Errorf(tcase.code, tcase.msg))