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fix: support MySQL driver’s conn check. #226

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Merged
enocom merged 8 commits into from
Jun 16, 2022
Merged

fix: support MySQL driver’s conn check. #226

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982cac3
fix: support MySQL diver's conn check.
enocom Jun 14, 2022
78de341
Merge branch 'main' into conn-check
enocom Jun 14, 2022
8613caa
Don't panic on failed type assertion
enocom Jun 14, 2022
af0b401
Use *tls.Conn.NetConn for raw connection
enocom Jun 14, 2022
658e297
tls.Conn.NetConn is Go 1.18 only
enocom Jun 14, 2022
21a7582
Add test to ensure compatability
enocom Jun 14, 2022
ea2503d
Merge branch 'main' into conn-check
enocom Jun 16, 2022
43df33e
Merge branch 'main' into conn-check
enocom Jun 16, 2022
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15 changes: 13 additions & 2 deletions dialer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@ import (
"strings"
"sync"
"sync/atomic"
"syscall"
"time"

"cloud.google.com/go/cloudsqlconn/errtype"
Expand Down Expand Up @@ -230,7 +231,7 @@ func (d *Dialer) Dial(ctx context.Context, instance string, opts ...DialOption)
trace.RecordDialLatency(ctx, instance, d.dialerID, latency)
}()

return newInstrumentedConn(tlsConn, func() {
return newInstrumentedConn(conn, tlsConn, func() {
n := atomic.AddUint64(&i.OpenConns, ^uint64(0))
trace.RecordOpenConnections(context.Background(), int64(n), d.dialerID, i.String())
}), nil
Expand Down Expand Up @@ -264,9 +265,10 @@ func (d *Dialer) Warmup(ctx context.Context, instance string, opts ...DialOption

// newInstrumentedConn initializes an instrumentedConn that on closing will
// decrement the number of open connects and record the result.
func newInstrumentedConn(conn net.Conn, closeFunc func()) *instrumentedConn {
func newInstrumentedConn(rawConn, conn net.Conn, closeFunc func()) *instrumentedConn {
return &instrumentedConn{
Conn: conn,
rawConn: rawConn,
closeFunc: closeFunc,
}
}
Expand All @@ -275,9 +277,18 @@ func newInstrumentedConn(conn net.Conn, closeFunc func()) *instrumentedConn {
// is closed.
type instrumentedConn struct {
net.Conn
// rawConn is the underlying net.Conn without TLS
rawConn net.Conn
closeFunc func()
}

// SyscallConn supports a connection check in the MySQL driver by delegating to
// the underlying non-TLS net.Conn.
func (i *instrumentedConn) SyscallConn() (syscall.RawConn, error) {
sconn := i.rawConn.(syscall.Conn)
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@Gentoli Gentoli Jun 14, 2022

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will this break on windows?

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@enocom enocom Jun 14, 2022 •
edited
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Good question. I'll add a unit test to make sure we have support in either case.

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@enocom enocom Jun 14, 2022

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Looks like the MySQL driver doesn't have support for Windows here: https://github.com/go-sql-driver/mysql/blob/ad9fa14acdcf7d0533e7fbe58728f3d216213ade/conncheck_dummy.go#L9. What would your expectation be?

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@enocom enocom Jun 14, 2022

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I've updated this so it won't panic if the type assertion fails. Separately, this builds on Windows with the unit test, so I think we're good.

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@Gentoli Gentoli Jun 14, 2022

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I would just expect it not to panic. (Parity to go mysql should be good)

humm I don't think returning an error will work with go mysql's current implementation. it will always trigger driver.ErrBadConn.

func (mc *mysqlConn) writePacket(data []byte) error {
	...
		if err == nil && mc.cfg.CheckConnLiveness {
			err = connCheck(conn)
		}
		if err != nil {
			errLog.Print("closing bad idle connection: ", err)
			mc.Close()
			return driver.ErrBadConn
		}
         ...

where connCheck():

func connCheck(conn net.Conn) error {
	...
	rawConn, err := sysConn.SyscallConn()
	if err != nil {
		return err
	}
	...
}

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@enocom enocom Jun 14, 2022

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I'll take another look at this and see what we can do. Thanks for all your help on this.

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@kurtisvg kurtisvg Jun 14, 2022

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It looks like the platforms that don't support the call won't use connCheck: https://github.com/go-sql-driver/mysql/blob/ad9fa14acdcf7d0533e7fbe58728f3d216213ade/conncheck_dummy.go#L16

So it seems like it's probably fine to return an error, since if it is being used something probably wrong?

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@enocom enocom Jun 14, 2022

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That’s my understanding as well. @Gentoli what do you think?

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@Gentoli Gentoli Jun 14, 2022

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Sorry I did not realize // +build is built-in to golang. Both with or without the check on the cast should work.

return sconn.SyscallConn()
}

// Close delegates to the underylying net.Conn interface and reports the close
// to the provided closeFunc only when Close returns no error.
func (i *instrumentedConn) Close() error {
Expand Down