Wrap healthcheck error only when in a tx

Signed-off-by: Florent Poinsard <florent.poinsard@outlook.fr>

go/vt/discovery/healthcheck.go

@@ -872,7 +872,7 @@ func (hc *HealthCheckImpl) TabletConnection(ctx context.Context, alias *topodata
 	hc.mu.Unlock()
 	if thc == nil || thc.Conn == nil {
 		// TODO: test that throws this error
-		return nil, vterrors.VT15001(vtrpc.Code_NOT_FOUND, fmt.Sprintf("tablet: %v is either down or nonexistent", alias))
+		return nil, vterrors.Errorf(vtrpc.Code_NOT_FOUND, "tablet: %v is either down or nonexistent", alias)
 	}
 	return thc.Connection(ctx), nil
 }

go/vt/vterrors/code.go

@@ -121,7 +121,7 @@ var (
 	VT14004 = errorWithoutState("VT14004", vtrpcpb.Code_UNAVAILABLE, "cannot find keyspace for: %s", "The specified keyspace could not be found.")
 	VT14005 = errorWithoutState("VT14005", vtrpcpb.Code_UNAVAILABLE, "cannot lookup sidecar database for keyspace: %s", "Failed to read sidecar database identifier.")
 
-	VT15001 = errorWithNoCode("VT15001", "transient error, please retry the transaction: %s", "The opened transaction should be closed by the application and re-tried.")
+	VT15001 = errorWithNoCode("VT15001", "transient transaction error, please issue a ROLLBACK and retry the transaction: %s", "The opened transaction must be ROLLBACK by the application and re-tried.")
 	VT15002 = errorWithoutState("VT15002", vtrpcpb.Code_FAILED_PRECONDITION, "previous transaction failed fatally: issue a ROLLBACK query in order to acknowledge the failed transaction", "This error appears after a VT15001 error was sent back to the client, future queries on the same session will fail until a ROLLBACK is explicitly sent to VTGate.")
 
 	// Errors is a list of errors that must match all the variables

go/vt/vtgate/scatter_conn.go

@@ -332,6 +332,10 @@ func getQueryService(ctx context.Context, rs *srvtopo.ResolvedShard, info *shard
 		return rs.Gateway, nil
 	}
 	qs, err := rs.Gateway.QueryServiceByAlias(ctx, info.alias, rs.Target)
+	if err != nil && info.transactionID != 0 {
+		err = vterrors.VT15001(vterrors.Code(err), err.Error())
+	}
+
 	if err == nil || skipReset {
 		return qs, err
 	}

go/vt/vtgate/tx_conn.go

@@ -166,7 +166,11 @@ func (txc *TxConn) queryService(ctx context.Context, alias *topodatapb.TabletAli
 	if alias == nil {
 		return txc.tabletGateway, nil
 	}
-	return txc.tabletGateway.QueryServiceByAlias(ctx, alias, nil)
+	qs, err := txc.tabletGateway.QueryServiceByAlias(ctx, alias, nil)
+	if err != nil {
+		return nil, vterrors.VT15001(vterrors.Code(err), err.Error())
+	}
+	return qs, nil
 }
 
 func (txc *TxConn) commitShard(ctx context.Context, s *vtgatepb.Session_ShardSession, logging *econtext.ExecuteLogger) error {