[chore]: Bump github.com/jackc/pgx/v5 from 5.5.5 to 5.6.0 (#2929)

vendor/github.com/jackc/pgx/v5/pgconn/pgconn.go

@@ -18,8 +18,8 @@ import (
 
 	"github.com/jackc/pgx/v5/internal/iobufpool"
 	"github.com/jackc/pgx/v5/internal/pgio"
+	"github.com/jackc/pgx/v5/pgconn/ctxwatch"
 	"github.com/jackc/pgx/v5/pgconn/internal/bgreader"
-	"github.com/jackc/pgx/v5/pgconn/internal/ctxwatch"
 	"github.com/jackc/pgx/v5/pgproto3"
 )
 
@@ -82,6 +82,8 @@ type PgConn struct {
 	slowWriteTimer    *time.Timer
 	bgReaderStarted   chan struct{}
 
+	customData map[string]any
+
 	config *Config
 
 	status byte // One of connStatus* constants
@@ -103,8 +105,9 @@ type PgConn struct {
 	cleanupDone chan struct{}
 }
 
-// Connect establishes a connection to a PostgreSQL server using the environment and connString (in URL or DSN format)
-// to provide configuration. See documentation for [ParseConfig] for details. ctx can be used to cancel a connect attempt.
+// Connect establishes a connection to a PostgreSQL server using the environment and connString (in URL or keyword/value
+// format) to provide configuration. See documentation for [ParseConfig] for details. ctx can be used to cancel a
+// connect attempt.
 func Connect(ctx context.Context, connString string) (*PgConn, error) {
 	config, err := ParseConfig(connString)
 	if err != nil {
@@ -114,9 +117,9 @@ func Connect(ctx context.Context, connString string) (*PgConn, error) {
 	return ConnectConfig(ctx, config)
 }
 
-// Connect establishes a connection to a PostgreSQL server using the environment and connString (in URL or DSN format)
-// and ParseConfigOptions to provide additional configuration. See documentation for [ParseConfig] for details. ctx can be
-// used to cancel a connect attempt.
+// Connect establishes a connection to a PostgreSQL server using the environment and connString (in URL or keyword/value
+// format) and ParseConfigOptions to provide additional configuration. See documentation for [ParseConfig] for details.
+// ctx can be used to cancel a connect attempt.
 func ConnectWithOptions(ctx context.Context, connString string, parseConfigOptions ParseConfigOptions) (*PgConn, error) {
 	config, err := ParseConfigWithOptions(connString, parseConfigOptions)
 	if err != nil {
@@ -131,15 +134,46 @@ func ConnectWithOptions(ctx context.Context, connString string, parseConfigOptio
 //
 // If config.Fallbacks are present they will sequentially be tried in case of error establishing network connection. An
 // authentication error will terminate the chain of attempts (like libpq:
-// https://www.postgresql.org/docs/11/libpq-connect.html#LIBPQ-MULTIPLE-HOSTS) and be returned as the error. Otherwise,
-// if all attempts fail the last error is returned.
-func ConnectConfig(octx context.Context, config *Config) (pgConn *PgConn, err error) {
+// https://www.postgresql.org/docs/11/libpq-connect.html#LIBPQ-MULTIPLE-HOSTS) and be returned as the error.
+func ConnectConfig(ctx context.Context, config *Config) (*PgConn, error) {
 	// Default values are set in ParseConfig. Enforce initial creation by ParseConfig rather than setting defaults from
 	// zero values.
 	if !config.createdByParseConfig {
 		panic("config must be created by ParseConfig")
 	}
 
+	var allErrors []error
+
+	connectConfigs, errs := buildConnectOneConfigs(ctx, config)
+	if len(errs) > 0 {
+		allErrors = append(allErrors, errs...)
+	}
+
+	if len(connectConfigs) == 0 {
+		return nil, &ConnectError{Config: config, err: fmt.Errorf("hostname resolving error: %w", errors.Join(allErrors...))}
+	}
+
+	pgConn, errs := connectPreferred(ctx, config, connectConfigs)
+	if len(errs) > 0 {
+		allErrors = append(allErrors, errs...)
+		return nil, &ConnectError{Config: config, err: errors.Join(allErrors...)}
+	}
+
+	if config.AfterConnect != nil {
+		err := config.AfterConnect(ctx, pgConn)
+		if err != nil {
+			pgConn.conn.Close()
+			return nil, &ConnectError{Config: config, err: fmt.Errorf("AfterConnect error: %w", err)}
+		}
+	}
+
+	return pgConn, nil
+}
+
+// buildConnectOneConfigs resolves hostnames and builds a list of connectOneConfigs to try connecting to. It returns a
+// slice of successfully resolved connectOneConfigs and a slice of errors. It is possible for both slices to contain
+// values if some hosts were successfully resolved and others were not.
+func buildConnectOneConfigs(ctx context.Context, config *Config) ([]*connectOneConfig, []error) {
 	// Simplify usage by treating primary config and fallbacks the same.
 	fallbackConfigs := []*FallbackConfig{
 		{
@@ -149,95 +183,28 @@ func ConnectConfig(octx context.Context, config *Config) (pgConn *PgConn, err er
 		},
 	}
 	fallbackConfigs = append(fallbackConfigs, config.Fallbacks...)
-	ctx := octx
-	fallbackConfigs, err = expandWithIPs(ctx, config.LookupFunc, fallbackConfigs)
-	if err != nil {
-		return nil, &ConnectError{Config: config, msg: "hostname resolving error", err: err}
-	}
 
-	if len(fallbackConfigs) == 0 {
-		return nil, &ConnectError{Config: config, msg: "hostname resolving error", err: errors.New("ip addr wasn't found")}
-	}
+	var configs []*connectOneConfig
 
-	foundBestServer := false
-	var fallbackConfig *FallbackConfig
-	for i, fc := range fallbackConfigs {
-		// ConnectTimeout restricts the whole connection process.
-		if config.ConnectTimeout != 0 {
-			// create new context first time or when previous host was different
-			if i == 0 || (fallbackConfigs[i].Host != fallbackConfigs[i-1].Host) {
-				var cancel context.CancelFunc
-				ctx, cancel = context.WithTimeout(octx, config.ConnectTimeout)
-				defer cancel()
-			}
-		} else {
-			ctx = octx
-		}
-		pgConn, err = connect(ctx, config, fc, false)
-		if err == nil {
-			foundBestServer = true
-			break
-		} else if pgerr, ok := err.(*PgError); ok {
-			err = &ConnectError{Config: config, msg: "server error", err: pgerr}
-			const ERRCODE_INVALID_PASSWORD = "28P01"                    // wrong password
-			const ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION = "28000" // wrong password or bad pg_hba.conf settings
-			const ERRCODE_INVALID_CATALOG_NAME = "3D000"                // db does not exist
-			const ERRCODE_INSUFFICIENT_PRIVILEGE = "42501"              // missing connect privilege
-			if pgerr.Code == ERRCODE_INVALID_PASSWORD ||
-				pgerr.Code == ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION && fc.TLSConfig != nil ||
-				pgerr.Code == ERRCODE_INVALID_CATALOG_NAME ||
-				pgerr.Code == ERRCODE_INSUFFICIENT_PRIVILEGE {
-				break
-			}
-		} else if cerr, ok := err.(*ConnectError); ok {
-			if _, ok := cerr.err.(*NotPreferredError); ok {
-				fallbackConfig = fc
-			}
-		}
-	}
+	var allErrors []error
 
-	if !foundBestServer && fallbackConfig != nil {
-		pgConn, err = connect(ctx, config, fallbackConfig, true)
-		if pgerr, ok := err.(*PgError); ok {
-			err = &ConnectError{Config: config, msg: "server error", err: pgerr}
-		}
-	}
-
-	if err != nil {
-		return nil, err // no need to wrap in connectError because it will already be wrapped in all cases except PgError
-	}
-
-	if config.AfterConnect != nil {
-		err := config.AfterConnect(ctx, pgConn)
-		if err != nil {
-			pgConn.conn.Close()
-			return nil, &ConnectError{Config: config, msg: "AfterConnect error", err: err}
-		}
-	}
-
-	return pgConn, nil
-}
-
-func expandWithIPs(ctx context.Context, lookupFn LookupFunc, fallbacks []*FallbackConfig) ([]*FallbackConfig, error) {
-	var configs []*FallbackConfig
-
-	var lookupErrors []error
-
-	for _, fb := range fallbacks {
+	for _, fb := range fallbackConfigs {
 		// skip resolve for unix sockets
 		if isAbsolutePath(fb.Host) {
-			configs = append(configs, &FallbackConfig{
-				Host:      fb.Host,
-				Port:      fb.Port,
-				TLSConfig: fb.TLSConfig,
+			network, address := NetworkAddress(fb.Host, fb.Port)
+			configs = append(configs, &connectOneConfig{
+				network:          network,
+				address:          address,
+				originalHostname: fb.Host,
+				tlsConfig:        fb.TLSConfig,
 			})
 
 			continue
 		}
 
-		ips, err := lookupFn(ctx, fb.Host)
+		ips, err := config.LookupFunc(ctx, fb.Host)
 		if err != nil {
-			lookupErrors = append(lookupErrors, err)
+			allErrors = append(allErrors, err)
 			continue
 		}
 
@@ -246,63 +213,126 @@ func expandWithIPs(ctx context.Context, lookupFn LookupFunc, fallbacks []*Fallba
 			if err == nil {
 				port, err := strconv.ParseUint(splitPort, 10, 16)
 				if err != nil {
-					return nil, fmt.Errorf("error parsing port (%s) from lookup: %w", splitPort, err)
+					return nil, []error{fmt.Errorf("error parsing port (%s) from lookup: %w", splitPort, err)}
 				}
-				configs = append(configs, &FallbackConfig{
-					Host:      splitIP,
-					Port:      uint16(port),
-					TLSConfig: fb.TLSConfig,
+				network, address := NetworkAddress(splitIP, uint16(port))
+				configs = append(configs, &connectOneConfig{
+					network:          network,
+					address:          address,
+					originalHostname: fb.Host,
+					tlsConfig:        fb.TLSConfig,
 				})
 			} else {
-				configs = append(configs, &FallbackConfig{
-					Host:      ip,
-					Port:      fb.Port,
-					TLSConfig: fb.TLSConfig,
+				network, address := NetworkAddress(ip, fb.Port)
+				configs = append(configs, &connectOneConfig{
+					network:          network,
+					address:          address,
+					originalHostname: fb.Host,
+					tlsConfig:        fb.TLSConfig,
 				})
 			}
 		}
 	}
 
-	// See https://github.com/jackc/pgx/issues/1464. When Go 1.20 can be used in pgx consider using errors.Join so all
-	// errors are reported.
-	if len(configs) == 0 && len(lookupErrors) > 0 {
-		return nil, lookupErrors[0]
-	}
-
-	return configs, nil
+	return configs, allErrors
 }
 
-func connect(ctx context.Context, config *Config, fallbackConfig *FallbackConfig,
+// connectPreferred attempts to connect to the preferred host from connectOneConfigs. The connections are attempted in
+// order. If a connection is successful it is returned. If no connection is successful then all errors are returned. If
+// a connection attempt returns a [NotPreferredError], then that host will be used if no other hosts are successful.
+func connectPreferred(ctx context.Context, config *Config, connectOneConfigs []*connectOneConfig) (*PgConn, []error) {
+	octx := ctx
+	var allErrors []error
+
+	var fallbackConnectOneConfig *connectOneConfig
+	for i, c := range connectOneConfigs {
+		// ConnectTimeout restricts the whole connection process.
+		if config.ConnectTimeout != 0 {
+			// create new context first time or when previous host was different
+			if i == 0 || (connectOneConfigs[i].address != connectOneConfigs[i-1].address) {
+				var cancel context.CancelFunc
+				ctx, cancel = context.WithTimeout(octx, config.ConnectTimeout)
+				defer cancel()
+			}
+		} else {
+			ctx = octx
+		}
+
+		pgConn, err := connectOne(ctx, config, c, false)
+		if pgConn != nil {
+			return pgConn, nil
+		}
+
+		allErrors = append(allErrors, err)
+
+		var pgErr *PgError
+		if errors.As(err, &pgErr) {
+			const ERRCODE_INVALID_PASSWORD = "28P01"                    // wrong password
+			const ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION = "28000" // wrong password or bad pg_hba.conf settings
+			const ERRCODE_INVALID_CATALOG_NAME = "3D000"                // db does not exist
+			const ERRCODE_INSUFFICIENT_PRIVILEGE = "42501"              // missing connect privilege
+			if pgErr.Code == ERRCODE_INVALID_PASSWORD ||
+				pgErr.Code == ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION && c.tlsConfig != nil ||
+				pgErr.Code == ERRCODE_INVALID_CATALOG_NAME ||
+				pgErr.Code == ERRCODE_INSUFFICIENT_PRIVILEGE {
+				return nil, allErrors
+			}
+		}
+
+		var npErr *NotPreferredError
+		if errors.As(err, &npErr) {
+			fallbackConnectOneConfig = c
+		}
+	}
+
+	if fallbackConnectOneConfig != nil {
+		pgConn, err := connectOne(ctx, config, fallbackConnectOneConfig, true)
+		if err == nil {
+			return pgConn, nil
+		}
+		allErrors = append(allErrors, err)
+	}
+
+	return nil, allErrors
+}
+
+// connectOne makes one connection attempt to a single host.
+func connectOne(ctx context.Context, config *Config, connectConfig *connectOneConfig,
 	ignoreNotPreferredErr bool,
 ) (*PgConn, error) {
 	pgConn := new(PgConn)
 	pgConn.config = config
 	pgConn.cleanupDone = make(chan struct{})
+	pgConn.customData = make(map[string]any)
 
 	var err error
-	network, address := NetworkAddress(fallbackConfig.Host, fallbackConfig.Port)
-	netConn, err := config.DialFunc(ctx, network, address)
-	if err != nil {
-		return nil, &ConnectError{Config: config, msg: "dial error", err: normalizeTimeoutError(ctx, err)}
+
+	newPerDialConnectError := func(msg string, err error) *perDialConnectError {
+		err = normalizeTimeoutError(ctx, err)
+		e := &perDialConnectError{address: connectConfig.address, originalHostname: connectConfig.originalHostname, err: fmt.Errorf("%s: %w", msg, err)}
+		return e
 	}
 
-	pgConn.conn = netConn
-	pgConn.contextWatcher = newContextWatcher(netConn)
-	pgConn.contextWatcher.Watch(ctx)
+	pgConn.conn, err = config.DialFunc(ctx, connectConfig.network, connectConfig.address)
+	if err != nil {
+		return nil, newPerDialConnectError("dial error", err)
+	}
 
-	if fallbackConfig.TLSConfig != nil {
-		nbTLSConn, err := startTLS(netConn, fallbackConfig.TLSConfig)
+	if connectConfig.tlsConfig != nil {
+		pgConn.contextWatcher = ctxwatch.NewContextWatcher(&DeadlineContextWatcherHandler{Conn: pgConn.conn})
+		pgConn.contextWatcher.Watch(ctx)
+		tlsConn, err := startTLS(pgConn.conn, connectConfig.tlsConfig)
 		pgConn.contextWatcher.Unwatch() // Always unwatch `netConn` after TLS.
 		if err != nil {
-			netConn.Close()
-			return nil, &ConnectError{Config: config, msg: "tls error", err: normalizeTimeoutError(ctx, err)}
+			pgConn.conn.Close()
+			return nil, newPerDialConnectError("tls error", err)
 		}
 
-		pgConn.conn = nbTLSConn
-		pgConn.contextWatcher = newContextWatcher(nbTLSConn)
-		pgConn.contextWatcher.Watch(ctx)
+		pgConn.conn = tlsConn
 	}
 
+	pgConn.contextWatcher = ctxwatch.NewContextWatcher(config.BuildContextWatcherHandler(pgConn))
+	pgConn.contextWatcher.Watch(ctx)
 	defer pgConn.contextWatcher.Unwatch()
 
 	pgConn.parameterStatuses = make(map[string]string)
@@ -336,7 +366,7 @@ func connect(ctx context.Context, config *Config, fallbackConfig *FallbackConfig
 	pgConn.frontend.Send(&startupMsg)
 	if err := pgConn.flushWithPotentialWriteReadDeadlock(); err != nil {
 		pgConn.conn.Close()
-		return nil, &ConnectError{Config: config, msg: "failed to write startup message", err: normalizeTimeoutError(ctx, err)}
+		return nil, newPerDialConnectError("failed to write startup message", err)
 	}
 
 	for {
@@ -344,9 +374,9 @@ func connect(ctx context.Context, config *Config, fallbackConfig *FallbackConfig
 		if err != nil {
 			pgConn.conn.Close()
 			if err, ok := err.(*PgError); ok {
-				return nil, err
+				return nil, newPerDialConnectError("server error", err)
 			}
-			return nil, &ConnectError{Config: config, msg: "failed to receive message", err: normalizeTimeoutError(ctx, err)}
+			return nil, newPerDialConnectError("failed to receive message", err)
 		}
 
 		switch msg := msg.(type) {
@@ -359,26 +389,26 @@ func connect(ctx context.Context, config *Config, fallbackConfig *FallbackConfig
 			err = pgConn.txPasswordMessage(pgConn.config.Password)
 			if err != nil {
 				pgConn.conn.Close()
-				return nil, &ConnectError{Config: config, msg: "failed to write password message", err: err}
+				return nil, newPerDialConnectError("failed to write password message", err)
 			}
 		case *pgproto3.AuthenticationMD5Password:
 			digestedPassword := "md5" + hexMD5(hexMD5(pgConn.config.Password+pgConn.config.User)+string(msg.Salt[:]))
 			err = pgConn.txPasswordMessage(digestedPassword)
 			if err != nil {
 				pgConn.conn.Close()
-				return nil, &ConnectError{Config: config, msg: "failed to write password message", err: err}
+				return nil, newPerDialConnectError("failed to write password message", err)
 			}
 		case *pgproto3.AuthenticationSASL:
 			err = pgConn.scramAuth(msg.AuthMechanisms)
 			if err != nil {
 				pgConn.conn.Close()
-				return nil, &ConnectError{Config: config, msg: "failed SASL auth", err: err}
+				return nil, newPerDialConnectError("failed SASL auth", err)
 			}
 		case *pgproto3.AuthenticationGSS:
 			err = pgConn.gssAuth()
 			if err != nil {
 				pgConn.conn.Close()
-				return nil, &ConnectError{Config: config, msg: "failed GSS auth", err: err}
+				return nil, newPerDialConnectError("failed GSS auth", err)
 			}
 		case *pgproto3.ReadyForQuery:
 			pgConn.status = connStatusIdle
@@ -396,7 +426,7 @@ func connect(ctx context.Context, config *Config, fallbackConfig *FallbackConfig
 						return pgConn, nil
 					}
 					pgConn.conn.Close()
-					return nil, &ConnectError{Config: config, msg: "ValidateConnect failed", err: err}
+					return nil, newPerDialConnectError("ValidateConnect failed", err)
 				}
 			}
 			return pgConn, nil
@@ -404,21 +434,14 @@ func connect(ctx context.Context, config *Config, fallbackConfig *FallbackConfig
 			// handled by ReceiveMessage
 		case *pgproto3.ErrorResponse:
 			pgConn.conn.Close()
-			return nil, ErrorResponseToPgError(msg)
+			return nil, newPerDialConnectError("server error", ErrorResponseToPgError(msg))
 		default:
 			pgConn.conn.Close()
-			return nil, &ConnectError{Config: config, msg: "received unexpected message", err: err}
+			return nil, newPerDialConnectError("received unexpected message", err)
 		}
 	}
 }
 
-func newContextWatcher(conn net.Conn) *ctxwatch.ContextWatcher {
-	return ctxwatch.NewContextWatcher(
-		func() { conn.SetDeadline(time.Date(1, 1, 1, 1, 1, 1, 1, time.UTC)) },
-		func() { conn.SetDeadline(time.Time{}) },
-	)
-}
-
 func startTLS(conn net.Conn, tlsConfig *tls.Config) (net.Conn, error) {
 	err := binary.Write(conn, binary.BigEndian, []int32{8, 80877103})
 	if err != nil {
@@ -928,23 +951,24 @@ func (pgConn *PgConn) Deallocate(ctx context.Context, name string) error {
 // ErrorResponseToPgError converts a wire protocol error message to a *PgError.
 func ErrorResponseToPgError(msg *pgproto3.ErrorResponse) *PgError {
 	return &PgError{
-		Severity:         msg.Severity,
-		Code:             string(msg.Code),
-		Message:          string(msg.Message),
-		Detail:           string(msg.Detail),
-		Hint:             msg.Hint,
-		Position:         msg.Position,
-		InternalPosition: msg.InternalPosition,
-		InternalQuery:    string(msg.InternalQuery),
-		Where:            string(msg.Where),
-		SchemaName:       string(msg.SchemaName),
-		TableName:        string(msg.TableName),
-		ColumnName:       string(msg.ColumnName),
-		DataTypeName:     string(msg.DataTypeName),
-		ConstraintName:   msg.ConstraintName,
-		File:             string(msg.File),
-		Line:             msg.Line,
-		Routine:          string(msg.Routine),
+		Severity:            msg.Severity,
+		SeverityUnlocalized: msg.SeverityUnlocalized,
+		Code:                string(msg.Code),
+		Message:             string(msg.Message),
+		Detail:              string(msg.Detail),
+		Hint:                msg.Hint,
+		Position:            msg.Position,
+		InternalPosition:    msg.InternalPosition,
+		InternalQuery:       string(msg.InternalQuery),
+		Where:               string(msg.Where),
+		SchemaName:          string(msg.SchemaName),
+		TableName:           string(msg.TableName),
+		ColumnName:          string(msg.ColumnName),
+		DataTypeName:        string(msg.DataTypeName),
+		ConstraintName:      msg.ConstraintName,
+		File:                string(msg.File),
+		Line:                msg.Line,
+		Routine:             string(msg.Routine),
 	}
 }
 
@@ -987,10 +1011,7 @@ func (pgConn *PgConn) CancelRequest(ctx context.Context) error {
 	defer cancelConn.Close()
 
 	if ctx != context.Background() {
-		contextWatcher := ctxwatch.NewContextWatcher(
-			func() { cancelConn.SetDeadline(time.Date(1, 1, 1, 1, 1, 1, 1, time.UTC)) },
-			func() { cancelConn.SetDeadline(time.Time{}) },
-		)
+		contextWatcher := ctxwatch.NewContextWatcher(&DeadlineContextWatcherHandler{Conn: cancelConn})
 		contextWatcher.Watch(ctx)
 		defer contextWatcher.Unwatch()
 	}
@@ -1523,8 +1544,10 @@ func (rr *ResultReader) Read() *Result {
 		values := rr.Values()
 		row := make([][]byte, len(values))
 		for i := range row {
-			row[i] = make([]byte, len(values[i]))
-			copy(row[i], values[i])
+			if values[i] != nil {
+				row[i] = make([]byte, len(values[i]))
+				copy(row[i], values[i])
+			}
 		}
 		br.Rows = append(br.Rows, row)
 	}
@@ -1879,6 +1902,11 @@ func (pgConn *PgConn) SyncConn(ctx context.Context) error {
 	return errors.New("SyncConn: conn never synchronized")
 }
 
+// CustomData returns a map that can be used to associate custom data with the connection.
+func (pgConn *PgConn) CustomData() map[string]any {
+	return pgConn.customData
+}
+
 // HijackedConn is the result of hijacking a connection.
 //
 // Due to the necessary exposure of internal implementation details, it is not covered by the semantic versioning
@@ -1891,6 +1919,7 @@ type HijackedConn struct {
 	TxStatus          byte
 	Frontend          *pgproto3.Frontend
 	Config            *Config
+	CustomData        map[string]any
 }
 
 // Hijack extracts the internal connection data. pgConn must be in an idle state. SyncConn should be called immediately
@@ -1913,6 +1942,7 @@ func (pgConn *PgConn) Hijack() (*HijackedConn, error) {
 		TxStatus:          pgConn.txStatus,
 		Frontend:          pgConn.frontend,
 		Config:            pgConn.config,
+		CustomData:        pgConn.customData,
 	}, nil
 }
 
@@ -1932,13 +1962,14 @@ func Construct(hc *HijackedConn) (*PgConn, error) {
 		txStatus:          hc.TxStatus,
 		frontend:          hc.Frontend,
 		config:            hc.Config,
+		customData:        hc.CustomData,
 
 		status: connStatusIdle,
 
 		cleanupDone: make(chan struct{}),
 	}
 
-	pgConn.contextWatcher = newContextWatcher(pgConn.conn)
+	pgConn.contextWatcher = ctxwatch.NewContextWatcher(hc.Config.BuildContextWatcherHandler(pgConn))
 	pgConn.bgReader = bgreader.New(pgConn.conn)
 	pgConn.slowWriteTimer = time.AfterFunc(time.Duration(math.MaxInt64),
 		func() {
@@ -2245,3 +2276,71 @@ func (p *Pipeline) Close() error {
 
 	return p.err
 }
+
+// DeadlineContextWatcherHandler handles canceled contexts by setting a deadline on a net.Conn.
+type DeadlineContextWatcherHandler struct {
+	Conn net.Conn
+
+	// DeadlineDelay is the delay to set on the deadline set on net.Conn when the context is canceled.
+	DeadlineDelay time.Duration
+}
+
+func (h *DeadlineContextWatcherHandler) HandleCancel(ctx context.Context) {
+	h.Conn.SetDeadline(time.Now().Add(h.DeadlineDelay))
+}
+
+func (h *DeadlineContextWatcherHandler) HandleUnwatchAfterCancel() {
+	h.Conn.SetDeadline(time.Time{})
+}
+
+// CancelRequestContextWatcherHandler handles canceled contexts by sending a cancel request to the server. It also sets
+// a deadline on a net.Conn as a fallback.
+type CancelRequestContextWatcherHandler struct {
+	Conn *PgConn
+
+	// CancelRequestDelay is the delay before sending the cancel request to the server.
+	CancelRequestDelay time.Duration
+
+	// DeadlineDelay is the delay to set on the deadline set on net.Conn when the context is canceled.
+	DeadlineDelay time.Duration
+
+	cancelFinishedChan             chan struct{}
+	handleUnwatchAfterCancelCalled func()
+}
+
+func (h *CancelRequestContextWatcherHandler) HandleCancel(context.Context) {
+	h.cancelFinishedChan = make(chan struct{})
+	var handleUnwatchedAfterCancelCalledCtx context.Context
+	handleUnwatchedAfterCancelCalledCtx, h.handleUnwatchAfterCancelCalled = context.WithCancel(context.Background())
+
+	deadline := time.Now().Add(h.DeadlineDelay)
+	h.Conn.conn.SetDeadline(deadline)
+
+	go func() {
+		defer close(h.cancelFinishedChan)
+
+		select {
+		case <-handleUnwatchedAfterCancelCalledCtx.Done():
+			return
+		case <-time.After(h.CancelRequestDelay):
+		}
+
+		cancelRequestCtx, cancel := context.WithDeadline(handleUnwatchedAfterCancelCalledCtx, deadline)
+		defer cancel()
+		h.Conn.CancelRequest(cancelRequestCtx)
+
+		// CancelRequest is inherently racy. Even though the cancel request has been received by the server at this point,
+		// it hasn't necessarily been delivered to the other connection. If we immediately return and the connection is
+		// immediately used then it is possible the CancelRequest will actually cancel our next query. The
+		// TestCancelRequestContextWatcherHandler Stress test can produce this error without the sleep below. The sleep time
+		// is arbitrary, but should be sufficient to prevent this error case.
+		time.Sleep(100 * time.Millisecond)
+	}()
+}
+
+func (h *CancelRequestContextWatcherHandler) HandleUnwatchAfterCancel() {
+	h.handleUnwatchAfterCancelCalled()
+	<-h.cancelFinishedChan
+
+	h.Conn.conn.SetDeadline(time.Time{})
+}