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database/sql: use errors.Is when checking ErrBadConn

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When drivers return driver.ErrBadConn, no meaningful
information about what the cause of the problem is
returned. Ideally the driver.ErrBadConn would be
always caught with the retry loop, but this is not
always the case. Drivers today must choose between
returning a useful error and use the rety logic.
This allows supporting both.

Fixes #47142

Change-Id: I454573028f041dfdf874eed6c254fb194ccf6d96
Reviewed-on: https://go-review.googlesource.com/c/go/+/333949
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Trust: Ian Lance Taylor <iant@golang.org>
Trust: Daniel Theophanes <kardianos@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Daniel Theophanes 2021-07-12 09:25:04 -05:00
parent d3f5dd5781
commit 1f368d5b86
4 changed files with 64 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
src/database/sql/driver/driver.go
View File

@ -156,6 +156,9 @@ var ErrSkip = errors.New("driver: skip fast-path; continue as if unimplemented")
// if there's a possibility that the database server might have
// performed the operation. Even if the server sends back an error,
// you shouldn't return ErrBadConn.
//
// Errors will be checked using errors.Is. An error may
// wrap ErrBadConn or implement the Is(error) bool method.
var ErrBadConn = errors.New("driver: bad connection")
// Pinger is an optional interface that may be implemented by a Conn.

27
src/database/sql/fakedb_test.go
View File

@ -96,6 +96,19 @@ type fakeDB struct {
allowAny bool
}
type fakeError struct {
Message string
Wrapped error
}
func (err fakeError) Error() string {
return err.Message
}
func (err fakeError) Unwrap() error {
return err.Wrapped
}
type table struct {
mu sync.Mutex
colname []string
@ -368,7 +381,7 @@ func (c *fakeConn) isDirtyAndMark() bool {
func (c *fakeConn) Begin() (driver.Tx, error) {
if c.isBad() {
return nil, driver.ErrBadConn
return nil, fakeError{Wrapped: driver.ErrBadConn}
}
if c.currTx != nil {
return nil, errors.New("fakedb: already in a transaction")
@ -401,7 +414,7 @@ func (c *fakeConn) ResetSession(ctx context.Context) error {
c.dirtySession = false
c.currTx = nil
if c.isBad() {
return driver.ErrBadConn
return fakeError{Message: "Reset Session: bad conn", Wrapped: driver.ErrBadConn}
}
return nil
}
@ -629,7 +642,7 @@ func (c *fakeConn) PrepareContext(ctx context.Context, query string) (driver.Stm
}
if c.stickyBad || (hookPrepareBadConn != nil && hookPrepareBadConn()) {
return nil, driver.ErrBadConn
return nil, fakeError{Message: "Preapre: Sticky Bad", Wrapped: driver.ErrBadConn}
}
c.touchMem()
@ -756,7 +769,7 @@ func (s *fakeStmt) ExecContext(ctx context.Context, args []driver.NamedValue) (d
}
if s.c.stickyBad || (hookExecBadConn != nil && hookExecBadConn()) {
return nil, driver.ErrBadConn
return nil, fakeError{Message: "Exec: Sticky Bad", Wrapped: driver.ErrBadConn}
}
if s.c.isDirtyAndMark() {
return nil, errFakeConnSessionDirty
@ -870,7 +883,7 @@ func (s *fakeStmt) QueryContext(ctx context.Context, args []driver.NamedValue) (
}
if s.c.stickyBad || (hookQueryBadConn != nil && hookQueryBadConn()) {
return nil, driver.ErrBadConn
return nil, fakeError{Message: "Query: Sticky Bad", Wrapped: driver.ErrBadConn}
}
if s.c.isDirtyAndMark() {
return nil, errFakeConnSessionDirty
@ -1031,7 +1044,7 @@ var hookCommitBadConn func() bool
func (tx *fakeTx) Commit() error {
tx.c.currTx = nil
if hookCommitBadConn != nil && hookCommitBadConn() {
return driver.ErrBadConn
return fakeError{Message: "Commit: Hook Bad Conn", Wrapped: driver.ErrBadConn}
}
tx.c.touchMem()
return nil
@ -1043,7 +1056,7 @@ var hookRollbackBadConn func() bool
func (tx *fakeTx) Rollback() error {
tx.c.currTx = nil
if hookRollbackBadConn != nil && hookRollbackBadConn() {
return driver.ErrBadConn
return fakeError{Message: "Rollback: Hook Bad Conn", Wrapped: driver.ErrBadConn}
}
tx.c.touchMem()
return nil

69
src/database/sql/sql.go
View File

@ -848,14 +848,15 @@ func (db *DB) pingDC(ctx context.Context, dc *driverConn, release func(error)) e
func (db *DB) PingContext(ctx context.Context) error {
var dc *driverConn
var err error
var isBadConn bool
for i := 0; i < maxBadConnRetries; i++ {
dc, err = db.conn(ctx, cachedOrNewConn)
if err != driver.ErrBadConn {
isBadConn = errors.Is(err, driver.ErrBadConn)
if !isBadConn {
break
}
}
if err == driver.ErrBadConn {
if isBadConn {
dc, err = db.conn(ctx, alwaysNewConn)
}
if err != nil {
@ -1317,9 +1318,9 @@ func (db *DB) conn(ctx context.Context, strategy connReuseStrategy) (*driverConn
db.mu.Unlock()
// Reset the session if required.
if err := conn.resetSession(ctx); err == driver.ErrBadConn {
if err := conn.resetSession(ctx); errors.Is(err, driver.ErrBadConn) {
conn.Close()
return nil, driver.ErrBadConn
return nil, err
}
return conn, nil
@ -1381,9 +1382,9 @@ func (db *DB) conn(ctx context.Context, strategy connReuseStrategy) (*driverConn
}
// Reset the session if required.
if err := ret.conn.resetSession(ctx); err == driver.ErrBadConn {
if err := ret.conn.resetSession(ctx); errors.Is(err, driver.ErrBadConn) {
ret.conn.Close()
return nil, driver.ErrBadConn
return nil, err
}
return ret.conn, ret.err
}
@ -1442,7 +1443,7 @@ const debugGetPut = false
// putConn adds a connection to the db's free pool.
// err is optionally the last error that occurred on this connection.
func (db *DB) putConn(dc *driverConn, err error, resetSession bool) {
if err != driver.ErrBadConn {
if !errors.Is(err, driver.ErrBadConn) {
if !dc.validateConnection(resetSession) {
err = driver.ErrBadConn
}
@ -1456,7 +1457,7 @@ func (db *DB) putConn(dc *driverConn, err error, resetSession bool) {
panic("sql: connection returned that was never out")
}
if err != driver.ErrBadConn && dc.expired(db.maxLifetime) {
if !errors.Is(err, driver.ErrBadConn) && dc.expired(db.maxLifetime) {
db.maxLifetimeClosed++
err = driver.ErrBadConn
}
@ -1471,7 +1472,7 @@ func (db *DB) putConn(dc *driverConn, err error, resetSession bool) {
}
dc.onPut = nil
if err == driver.ErrBadConn {
if errors.Is(err, driver.ErrBadConn) {
// Don't reuse bad connections.
// Since the conn is considered bad and is being discarded, treat it
// as closed. Don't decrement the open count here, finalClose will
@ -1551,13 +1552,15 @@ const maxBadConnRetries = 2
func (db *DB) PrepareContext(ctx context.Context, query string) (*Stmt, error) {
var stmt *Stmt
var err error
var isBadConn bool
for i := 0; i < maxBadConnRetries; i++ {
stmt, err = db.prepare(ctx, query, cachedOrNewConn)
if err != driver.ErrBadConn {
isBadConn = errors.Is(err, driver.ErrBadConn)
if !isBadConn {
break
}
}
if err == driver.ErrBadConn {
if isBadConn {
return db.prepare(ctx, query, alwaysNewConn)
}
return stmt, err
@ -1627,13 +1630,15 @@ func (db *DB) prepareDC(ctx context.Context, dc *driverConn, release func(error)
func (db *DB) ExecContext(ctx context.Context, query string, args ...interface{}) (Result, error) {
var res Result
var err error
var isBadConn bool
for i := 0; i < maxBadConnRetries; i++ {
res, err = db.exec(ctx, query, args, cachedOrNewConn)
if err != driver.ErrBadConn {
isBadConn = errors.Is(err, driver.ErrBadConn)
if !isBadConn {
break
}
}
if err == driver.ErrBadConn {
if isBadConn {
return db.exec(ctx, query, args, alwaysNewConn)
}
return res, err
@ -1700,13 +1705,15 @@ func (db *DB) execDC(ctx context.Context, dc *driverConn, release func(error), q
func (db *DB) QueryContext(ctx context.Context, query string, args ...interface{}) (*Rows, error) {
var rows *Rows
var err error
var isBadConn bool
for i := 0; i < maxBadConnRetries; i++ {
rows, err = db.query(ctx, query, args, cachedOrNewConn)
if err != driver.ErrBadConn {
isBadConn = errors.Is(err, driver.ErrBadConn)
if !isBadConn {
break
}
}
if err == driver.ErrBadConn {
if isBadConn {
return db.query(ctx, query, args, alwaysNewConn)
}
return rows, err
@ -1835,13 +1842,15 @@ func (db *DB) QueryRow(query string, args ...interface{}) *Row {
func (db *DB) BeginTx(ctx context.Context, opts *TxOptions) (*Tx, error) {
var tx *Tx
var err error
var isBadConn bool
for i := 0; i < maxBadConnRetries; i++ {
tx, err = db.begin(ctx, opts, cachedOrNewConn)
if err != driver.ErrBadConn {
isBadConn = errors.Is(err, driver.ErrBadConn)
if !isBadConn {
break
}
}
if err == driver.ErrBadConn {
if isBadConn {
return db.begin(ctx, opts, alwaysNewConn)
}
return tx, err
@ -1914,13 +1923,15 @@ var ErrConnDone = errors.New("sql: connection is already closed")
func (db *DB) Conn(ctx context.Context) (*Conn, error) {
var dc *driverConn
var err error
var isBadConn bool
for i := 0; i < maxBadConnRetries; i++ {
dc, err = db.conn(ctx, cachedOrNewConn)
if err != driver.ErrBadConn {
isBadConn = errors.Is(err, driver.ErrBadConn)
if !isBadConn {
break
}
}
if err == driver.ErrBadConn {
if isBadConn {
dc, err = db.conn(ctx, alwaysNewConn)
}
if err != nil {
@ -2032,8 +2043,8 @@ func (c *Conn) PrepareContext(ctx context.Context, query string) (*Stmt, error)
// Raw executes f exposing the underlying driver connection for the
// duration of f. The driverConn must not be used outside of f.
//
// Once f returns and err is not equal to driver.ErrBadConn, the Conn will
// continue to be usable until Conn.Close is called.
// Once f returns and err is not driver.ErrBadConn, the Conn will continue to be usable
// until Conn.Close is called.
func (c *Conn) Raw(f func(driverConn interface{}) error) (err error) {
var dc *driverConn
var release releaseConn
@ -2084,7 +2095,7 @@ func (c *Conn) BeginTx(ctx context.Context, opts *TxOptions) (*Tx, error) {
// as the sql operation is done with the dc.
func (c *Conn) closemuRUnlockCondReleaseConn(err error) {
c.closemu.RUnlock()
if err == driver.ErrBadConn {
if errors.Is(err, driver.ErrBadConn) {
c.close(err)
}
}
@ -2278,7 +2289,7 @@ func (tx *Tx) Commit() error {
withLock(tx.dc, func() {
err = tx.txi.Commit()
})
if err != driver.ErrBadConn {
if !errors.Is(err, driver.ErrBadConn) {
tx.closePrepared()
}
tx.close(err)
@ -2310,7 +2321,7 @@ func (tx *Tx) rollback(discardConn bool) error {
withLock(tx.dc, func() {
err = tx.txi.Rollback()
})
if err != driver.ErrBadConn {
if !errors.Is(err, driver.ErrBadConn) {
tx.closePrepared()
}
if discardConn {
@ -2616,7 +2627,7 @@ func (s *Stmt) ExecContext(ctx context.Context, args ...interface{}) (Result, er
}
dc, releaseConn, ds, err := s.connStmt(ctx, strategy)
if err != nil {
if err == driver.ErrBadConn {
if errors.Is(err, driver.ErrBadConn) {
continue
}
return nil, err
@ -2624,7 +2635,7 @@ func (s *Stmt) ExecContext(ctx context.Context, args ...interface{}) (Result, er
res, err = resultFromStatement(ctx, dc.ci, ds, args...)
releaseConn(err)
if err != driver.ErrBadConn {
if !errors.Is(err, driver.ErrBadConn) {
return res, err
}
}
@ -2764,7 +2775,7 @@ func (s *Stmt) QueryContext(ctx context.Context, args ...interface{}) (*Rows, er
}
dc, releaseConn, ds, err := s.connStmt(ctx, strategy)
if err != nil {
if err == driver.ErrBadConn {
if errors.Is(err, driver.ErrBadConn) {
continue
}
return nil, err
@ -2798,7 +2809,7 @@ func (s *Stmt) QueryContext(ctx context.Context, args ...interface{}) (*Rows, er
}
releaseConn(err)
if err != driver.ErrBadConn {
if !errors.Is(err, driver.ErrBadConn) {
return nil, err
}
}

2
src/database/sql/sql_test.go
View File

@ -3159,7 +3159,7 @@ func TestTxEndBadConn(t *testing.T) {
return broken
}
if err := op(); err != driver.ErrBadConn {
if err := op(); !errors.Is(err, driver.ErrBadConn) {
t.Errorf(name+": %v", err)
return
}