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// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package database
import (
// RegisterOCWrapper registers a driver that wraps the OpenCensus driver, which in
// turn wraps the driver named as the first argument.
func RegisterOCWrapper(driverName string, opts ...ocsql.TraceOption) (string, error) {
// Get the driver to wrap.
db, err := sql.Open(driverName, "")
if err != nil {
return "", err
dri := db.Driver()
if err := db.Close(); err != nil {
return "", err
name := "ocWrapper-" + driverName
sql.Register(name, &wrapOCDriver{dri, opts})
return name, nil
type wrapOCDriver struct {
underlying driver.Driver
opts []ocsql.TraceOption
// Open implements database/sql/driver.Driver.
func (d *wrapOCDriver) Open(name string) (driver.Conn, error) {
conn, err := d.underlying.Open(name)
if err != nil {
return nil, err
oc := ocsql.WrapConn(conn, d.opts...)
return &wrapConn{conn, oc.(iconn)}, nil
type iconn interface {
// A wrapConn knows about both the underlying Conn, and the OpenCensus Conn that wraps it.
// It delegates all calls to the OpenCensus Conn, but the underlying conn is available
// to this package.
type wrapConn struct {
underlying driver.Conn
oc iconn
// Ping and all the following methods implement driver.Conn and related interfaces,
// listed in the iconn interface above.
func (c *wrapConn) Ping(ctx context.Context) error { return c.oc.Ping(ctx) }
func (c *wrapConn) Prepare(query string) (driver.Stmt, error) { return c.oc.Prepare(query) }
func (c *wrapConn) Close() error { return c.oc.Close() }
func (c *wrapConn) Begin() (driver.Tx, error) { return nil, errors.New("unimplmented") }
func (c *wrapConn) ExecContext(ctx context.Context, q string, args []driver.NamedValue) (driver.Result, error) {
return c.oc.ExecContext(ctx, q, args)
func (c *wrapConn) QueryContext(ctx context.Context, q string, args []driver.NamedValue) (driver.Rows, error) {
return c.oc.QueryContext(ctx, q, args)
func (c *wrapConn) PrepareContext(ctx context.Context, query string) (driver.Stmt, error) {
return c.oc.PrepareContext(ctx, query)
func (c *wrapConn) BeginTx(ctx context.Context, opts driver.TxOptions) (driver.Tx, error) {
return c.oc.BeginTx(ctx, opts)