// NewQueryResultReaderForTablet creates a new QueryResultReader for
// the provided tablet / sql query
func NewQueryResultReaderForTablet(ts topo.Server, tabletAlias topo.TabletAlias, sql string) (*QueryResultReader, error) {
tablet, err := ts.GetTablet(tabletAlias)
if err != nil {
return nil, err
}
endPoint, err := tablet.EndPoint()
if err != nil {
return nil, err
}
conn, err := tabletconn.GetDialer()(context.TODO(), *endPoint, tablet.Keyspace, tablet.Shard, 30*time.Second)
if err != nil {
return nil, err
}
sr, clientErrFn, err := conn.StreamExecute(context.TODO(), sql, make(map[string]interface{}), 0)
if err != nil {
return nil, err
}
// read the columns, or grab the error
cols, ok := <-sr
if !ok {
return nil, fmt.Errorf("Cannot read Fields for query '%v': %v", sql, clientErrFn())
}
return &QueryResultReader{
Output: sr,
Fields: cols.Fields,
conn: conn,
clientErrFn: clientErrFn,
}, nil
}
// getConn reuses an existing connection if possible. Otherwise
// it returns a connection which it will save for future reuse.
// If it returns an error, retry will tell you if getConn can be retried.
// If the context has a deadline and exceeded, it returns error and no-retry immediately.
func (sdc *ShardConn) getConn(ctx context.Context) (conn tabletconn.TabletConn, endPoint topo.EndPoint, err error, retry bool) {
sdc.mu.Lock()
defer sdc.mu.Unlock()
// fail-fast if deadline exceeded
deadline, ok := ctx.Deadline()
if ok {
if time.Now().After(deadline) {
return nil, topo.EndPoint{}, tabletconn.OperationalError("vttablet: deadline exceeded"), false
}
}
if sdc.conn != nil {
return sdc.conn, sdc.conn.EndPoint(), nil, false
}
endPoint, err = sdc.balancer.Get()
if err != nil {
return nil, topo.EndPoint{}, err, false
}
conn, err = tabletconn.GetDialer()(ctx, endPoint, sdc.keyspace, sdc.shard, sdc.timeout)
if err != nil {
sdc.balancer.MarkDown(endPoint.Uid, err.Error())
return nil, endPoint, err, true
}
sdc.conn = conn
return sdc.conn, endPoint, nil, false
}
func (conn *Conn) dial() (err error) {
// build the endpoint in the right format
host, port, err := netutil.SplitHostPort(conn.dbi.Host)
if err != nil {
return err
}
endPoint := topo.EndPoint{
Host: host,
NamedPortMap: map[string]int{
"_vtocc": port,
},
}
// and dial
tabletConn, err := tabletconn.GetDialer()(context.TODO(), endPoint, conn.keyspace(), conn.shard(), conn.timeout)
if err != nil {
return err
}
conn.tabletConn = tabletConn
return
}