driver.go

/*
Copyright 2019 The Vitess Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package vitessdriver

import (
	"context"
	"database/sql"
	"database/sql/driver"
	"encoding/base64"
	"encoding/json"
	"errors"
	"fmt"

	"google.golang.org/grpc"

	"vitess.io/vitess/go/sqltypes"
	querypb "vitess.io/vitess/go/vt/proto/query"
	vtgatepb "vitess.io/vitess/go/vt/proto/vtgate"
	"vitess.io/vitess/go/vt/vtgate/grpcvtgateconn"
	"vitess.io/vitess/go/vt/vtgate/vtgateconn"
)

var (
	errNoIntermixing        = errors.New("named and positional arguments intermixing disallowed")
	errIsolationUnsupported = errors.New("isolation levels are not supported")
)

// Type-check interfaces.
var (
	_ interface {
		driver.Connector
	} = &connector{}

	_ interface {
		driver.Driver
		driver.DriverContext
	} = drv{}

	_ interface {
		driver.Conn
		driver.ConnBeginTx
		driver.ConnPrepareContext
		driver.ExecerContext
		driver.Pinger
		driver.QueryerContext
		driver.Tx
	} = &conn{}

	_ interface {
		driver.Stmt
		driver.StmtExecContext
		driver.StmtQueryContext
	} = &stmt{}
)

func init() {
	sql.Register("vitess", drv{})
}

// Open is a Vitess helper function for sql.Open().
//
// It opens a database connection to vtgate running at "address".
func Open(address, target string) (*sql.DB, error) {
	c := Configuration{
		Address: address,
		Target:  target,
	}
	return OpenWithConfiguration(c)
}

// OpenForStreaming is the same as Open() but uses streaming RPCs to retrieve
// the results.
//
// The streaming mode is recommended for large results.
func OpenForStreaming(address, target string) (*sql.DB, error) {
	c := Configuration{
		Address:   address,
		Target:    target,
		Streaming: true,
	}
	return OpenWithConfiguration(c)
}

// OpenWithConfiguration is the generic Vitess helper function for sql.Open().
//
// It allows to pass in a Configuration struct to control all possible
// settings of the Vitess Go SQL driver.
func OpenWithConfiguration(c Configuration) (*sql.DB, error) {
	c.setDefaults()

	json, err := c.toJSON()
	if err != nil {
		return nil, err
	}

	if len(c.GRPCDialOptions) != 0 {
		vtgateconn.RegisterDialer(c.Protocol, grpcvtgateconn.Dial(c.GRPCDialOptions...))
	}

	return sql.Open(c.DriverName, json)
}

type drv struct{}

// Open implements the database/sql/driver.Driver interface.
//
// For "name", the Vitess driver requires that a JSON object is passed in.
//
// Instead of using this call and passing in a hand-crafted JSON string, it's
// recommended to use the public Vitess helper functions like
// Open(), OpenShard() or OpenWithConfiguration() instead. These will generate
// the required JSON string behind the scenes for you.
//
// Example for a JSON string:
//
//	{"protocol": "grpc", "address": "localhost:1111", "target": "@primary"}
//
// For a description of the available fields, see the Configuration struct.
func (d drv) Open(name string) (driver.Conn, error) {
	conn, err := d.OpenConnector(name)
	if err != nil {
		return nil, err
	}

	return conn.Connect(context.Background())
}

// OpenConnector implements the database/sql/driver.DriverContext interface.
//
// See the documentation of Open for details on the format of name.
func (d drv) OpenConnector(name string) (driver.Connector, error) {
	var cfg Configuration
	if err := json.Unmarshal([]byte(name), &cfg); err != nil {
		return nil, err
	}

	cfg.setDefaults()
	return d.newConnector(cfg)
}

// A connector holds immutable state for the creation of additional conns via
// the Connect method.
type connector struct {
	drv     drv
	cfg     Configuration
	convert *converter
}

func (d drv) newConnector(cfg Configuration) (driver.Connector, error) {
	convert, err := newConverter(&cfg)
	if err != nil {
		return nil, err
	}

	return &connector{
		drv:     d,
		cfg:     cfg,
		convert: convert,
	}, nil
}

// Connect implements the database/sql/driver.Connector interface.
func (c *connector) Connect(ctx context.Context) (driver.Conn, error) {
	conn := &conn{
		cfg:     c.cfg,
		convert: c.convert,
	}

	if err := conn.dial(ctx); err != nil {
		return nil, err
	}

	return conn, nil
}

// Driver implements the database/sql/driver.Connector interface.
func (c *connector) Driver() driver.Driver { return c.drv }

// Configuration holds all Vitess driver settings.
//
// Fields with documented default values do not have to be set explicitly.
type Configuration struct {
	// Protocol is the name of the vtgate RPC client implementation.
	// Note: In open-source "grpc" is the recommended implementation.
	//
	// Default: "grpc"
	Protocol string

	// Address must point to a vtgate instance.
	//
	// Format: hostname:port
	Address string

	// Target specifies the default target.
	Target string

	// Streaming is true when streaming RPCs are used.
	// Recommended for large results.
	// Default: false
	Streaming bool

	// DefaultLocation is the timezone string that will be used
	// when converting DATETIME and DATE into time.Time.
	// This setting has no effect if ConvertDatetime is not set.
	// Default: UTC
	DefaultLocation string

	// GRPCDialOptions registers a new vtgateconn dialer with these dial options using the
	// protocol as the key. This may overwrite the default grpcvtgateconn dial option
	// if a custom one hasn't been specified in the config.
	//
	// Default: none
	GRPCDialOptions []grpc.DialOption `json:"-"`

	// Driver is the name registered with the database/sql package. This override
	// is here in case you have wrapped the driver for stats or other interceptors.
	//
	// Default: "vitess"
	DriverName string `json:"-"`

	// SessionToken is a protobuf encoded vtgatepb.Session represented as base64, which
	// can be used to distribute a transaction over the wire.
	SessionToken string
}

// toJSON converts Configuration to the JSON string which is required by the
// Vitess driver. Default values for empty fields will be set.
func (c Configuration) toJSON() (string, error) {
	jsonBytes, err := json.Marshal(c)
	if err != nil {
		return "", err
	}
	return string(jsonBytes), nil
}

// setDefaults sets the default values for empty fields.
func (c *Configuration) setDefaults() {
	// if no protocol is provided default to grpc so the driver is in control
	// of the connection protocol and not the flag vtgateconn.VtgateProtocol
	if c.Protocol == "" {
		c.Protocol = "grpc"
	}

	if c.DriverName == "" {
		c.DriverName = "vitess"
	}
}

type conn struct {
	cfg     Configuration
	convert *converter
	conn    *vtgateconn.VTGateConn
	session *vtgateconn.VTGateSession
}

func (c *conn) dial(ctx context.Context) error {
	var err error
	c.conn, err = vtgateconn.DialProtocol(ctx, c.cfg.Protocol, c.cfg.Address)
	if err != nil {
		return err
	}
	if c.cfg.SessionToken != "" {
		sessionFromToken, err := sessionTokenToSession(c.cfg.SessionToken)
		if err != nil {
			return err
		}
		c.session = c.conn.SessionFromPb(sessionFromToken)
	} else {
		c.session = c.conn.Session(c.cfg.Target, nil)
	}
	return nil
}

func (c *conn) Ping(ctx context.Context) error {
	if c.cfg.Streaming {
		return errors.New("Ping not allowed for streaming connections")
	}

	_, err := c.ExecContext(ctx, "select 1", nil)
	return err
}

func (c *conn) Prepare(query string) (driver.Stmt, error) {
	return &stmt{c: c, query: query}, nil
}

func (c *conn) PrepareContext(ctx context.Context, query string) (driver.Stmt, error) {
	return c.Prepare(query)
}

func (c *conn) Close() error {
	c.conn.Close()
	return nil
}

// DistributedTxFromSessionToken allows users to send serialized sessions over the wire and
// reconnect to an existing transaction. Setting the sessionToken and address on the
// supplied configuration is the minimum required
// WARNING: the original Tx must already have already done work on all shards to be affected,
// otherwise the ShardSessions will not be sent through in the session token, and thus will
// never be committed in the source. The returned validation function checks to make sure that
// the new transaction work has not added any new ShardSessions.
func DistributedTxFromSessionToken(ctx context.Context, c Configuration) (*sql.Tx, func() error, error) {
	if c.SessionToken == "" {
		return nil, nil, errors.New("c.SessionToken is required")
	}

	session, err := sessionTokenToSession(c.SessionToken)
	if err != nil {
		return nil, nil, err
	}

	// if there isn't 1 or more shards already referenced, no work in this Tx can be committed
	originalShardSessionCount := len(session.ShardSessions)
	if originalShardSessionCount == 0 {
		return nil, nil, errors.New("there must be at least 1 ShardSession")
	}

	db, err := OpenWithConfiguration(c)
	if err != nil {
		return nil, nil, err
	}

	// this should return the only connection associated with the db
	tx, err := db.BeginTx(ctx, nil)
	if err != nil {
		return nil, nil, err
	}

	// this is designed to be run after all new work has been done in the tx, similar to
	// where you would traditionally run a tx.Commit, to help prevent you from silently
	// losing transactional data.
	validationFunc := func() error {
		var sessionToken string
		sessionToken, err = SessionTokenFromTx(ctx, tx)
		if err != nil {
			return err
		}

		session, err = sessionTokenToSession(sessionToken)
		if err != nil {
			return err
		}

		if len(session.ShardSessions) > originalShardSessionCount {
			return fmt.Errorf("mismatched ShardSession count: originally %d, now %d",
				originalShardSessionCount, len(session.ShardSessions),
			)
		}

		return nil
	}

	return tx, validationFunc, nil
}

// SessionTokenFromTx serializes the sessionFromToken on the tx, which can be reconstituted
// into a *sql.Tx using DistributedTxFromSessionToken
func SessionTokenFromTx(ctx context.Context, tx *sql.Tx) (string, error) {
	var sessionToken string

	err := tx.QueryRowContext(ctx, "vt_session_token").Scan(&sessionToken)
	if err != nil {
		return "", err
	}

	session, err := sessionTokenToSession(sessionToken)
	if err != nil {
		return "", err
	}

	// if there isn't 1 or more shards already referenced, no work in this Tx can be committed
	originalShardSessionCount := len(session.ShardSessions)
	if originalShardSessionCount == 0 {
		return "", errors.New("there must be at least 1 ShardSession")
	}

	return sessionToken, nil
}

func newSessionTokenRow(session *vtgatepb.Session, c *converter) (driver.Rows, error) {
	sessionToken, err := sessionToSessionToken(session)
	if err != nil {
		return nil, err
	}

	qr := sqltypes.Result{
		Fields: []*querypb.Field{{
			Name: "vt_session_token",
			Type: sqltypes.VarBinary,
		}},
		Rows: [][]sqltypes.Value{{
			sqltypes.NewVarBinary(sessionToken),
		}},
	}

	return newRows(&qr, c), nil
}

func sessionToSessionToken(session *vtgatepb.Session) (string, error) {
	b, err := session.MarshalVT()
	if err != nil {
		return "", err
	}

	return base64.StdEncoding.EncodeToString(b), nil
}

func sessionTokenToSession(sessionToken string) (*vtgatepb.Session, error) {
	b, err := base64.StdEncoding.DecodeString(sessionToken)
	if err != nil {
		return nil, err
	}

	session := &vtgatepb.Session{}
	err = session.UnmarshalVT(b)
	if err != nil {
		return nil, err
	}

	return session, nil
}

func (c *conn) Begin() (driver.Tx, error) {
	// if we're loading from an existing session, we need to avoid starting a new transaction
	if c.cfg.SessionToken != "" {
		return c, nil
	}

	if _, err := c.Exec("begin", nil); err != nil {
		return nil, err
	}
	return c, nil
}

func (c *conn) BeginTx(_ context.Context, opts driver.TxOptions) (driver.Tx, error) {
	// We don't use the context. The function signature accepts the context
	// to signal to the driver that it's allowed to call Rollback on Cancel.
	if opts.Isolation != driver.IsolationLevel(0) || opts.ReadOnly {
		return nil, errIsolationUnsupported
	}
	return c.Begin()
}

func (c *conn) Commit() error {
	// if we're loading from an existing session, disallow committing/rolling back the transaction
	// this isn't a technical limitation, but is enforced to prevent misuse, so that only
	// the original creator of the transaction can commit/rollback
	if c.cfg.SessionToken != "" {
		return errors.New("calling Commit from a distributed tx is not allowed")
	}

	_, err := c.Exec("commit", nil)
	return err
}

func (c *conn) Rollback() error {
	// if we're loading from an existing session, disallow committing/rolling back the transaction
	// this isn't a technical limitation, but is enforced to prevent misuse, so that only
	// the original creator of the transaction can commit/rollback
	if c.cfg.SessionToken != "" {
		return errors.New("calling Rollback from a distributed tx is not allowed")
	}

	_, err := c.Exec("rollback", nil)
	return err
}

func (c *conn) Exec(query string, args []driver.Value) (driver.Result, error) {
	ctx := context.TODO()

	if c.cfg.Streaming {
		return nil, errors.New("Exec not allowed for streaming connections")
	}
	bindVars, err := c.convert.buildBindVars(args)
	if err != nil {
		return nil, err
	}

	qr, err := c.session.Execute(ctx, query, bindVars)
	if err != nil {
		return nil, err
	}
	return result{int64(qr.InsertID), int64(qr.RowsAffected)}, nil
}

func (c *conn) ExecContext(ctx context.Context, query string, args []driver.NamedValue) (driver.Result, error) {
	if c.cfg.Streaming {
		return nil, errors.New("Exec not allowed for streaming connections")
	}

	bv, err := c.convert.bindVarsFromNamedValues(args)
	if err != nil {
		return nil, err
	}
	qr, err := c.session.Execute(ctx, query, bv)
	if err != nil {
		return nil, err
	}
	return result{int64(qr.InsertID), int64(qr.RowsAffected)}, nil
}

func (c *conn) Query(query string, args []driver.Value) (driver.Rows, error) {
	ctx := context.TODO()
	bindVars, err := c.convert.buildBindVars(args)
	if err != nil {
		return nil, err
	}

	if c.cfg.Streaming {
		stream, err := c.session.StreamExecute(ctx, query, bindVars)
		if err != nil {
			return nil, err
		}
		return newStreamingRows(stream, c.convert), nil
	}

	qr, err := c.session.Execute(ctx, query, bindVars)
	if err != nil {
		return nil, err
	}
	return newRows(qr, c.convert), nil
}

func (c *conn) QueryContext(ctx context.Context, query string, args []driver.NamedValue) (driver.Rows, error) {
	// special case for serializing the current sessionFromToken state
	if query == "vt_session_token" {
		return newSessionTokenRow(c.session.SessionPb(), c.convert)
	}

	bv, err := c.convert.bindVarsFromNamedValues(args)
	if err != nil {
		return nil, err
	}

	if c.cfg.Streaming {
		stream, err := c.session.StreamExecute(ctx, query, bv)
		if err != nil {
			return nil, err
		}
		return newStreamingRows(stream, c.convert), nil
	}

	qr, err := c.session.Execute(ctx, query, bv)
	if err != nil {
		return nil, err
	}
	return newRows(qr, c.convert), nil
}

type stmt struct {
	c     *conn
	query string
}

func (s *stmt) Close() error {
	return nil
}

func (s *stmt) NumInput() int {
	// -1 = Golang sql won't sanity check argument counts before Exec or Query.
	return -1
}

func (s *stmt) Exec(args []driver.Value) (driver.Result, error) {
	return s.c.Exec(s.query, args)
}

func (s *stmt) ExecContext(ctx context.Context, args []driver.NamedValue) (driver.Result, error) {
	return s.c.ExecContext(ctx, s.query, args)
}

func (s *stmt) Query(args []driver.Value) (driver.Rows, error) {
	return s.c.Query(s.query, args)
}

func (s *stmt) QueryContext(ctx context.Context, args []driver.NamedValue) (driver.Rows, error) {
	return s.c.QueryContext(ctx, s.query, args)
}

type result struct {
	insertid, rowsaffected int64
}

func (r result) LastInsertId() (int64, error) {
	return r.insertid, nil
}

func (r result) RowsAffected() (int64, error) {
	return r.rowsaffected, nil
}