ConnPool check fd for bad conns (#1824)

* conncheck for badconn (#1821)

* format imports

* fix ut: pool with badconn

* fix unstable ut: should facilitate failover

* Revert "fix unstable ut: should facilitate failover"

This reverts commit c7eeca2a5c.

* fix test error

Signed-off-by: monkey92t <golang@88.com>

Co-authored-by: hidu <duv123+github@gmail.com>
Co-authored-by: monkey92t <golang@88.com>

internal/pool/main_test.go

@@ -2,9 +2,12 @@ package pool_test
 
 import (
 	"context"
+	"fmt"
 	"net"
 	"sync"
+	"syscall"
 	"testing"
+	"time"
 
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
@@ -32,5 +35,87 @@ func perform(n int, cbs ...func(int)) {
 }
 
 func dummyDialer(context.Context) (net.Conn, error) {
-	return &net.TCPConn{}, nil
+	// return &net.TCPConn{}, nil
+	return newDummyConn(), nil
+}
+
+func newDummyConn() net.Conn {
+	return &dummyConn{
+		rawConn: &dummyRawConn{},
+	}
+}
+
+var _ net.Conn = (*dummyConn)(nil)
+var _ syscall.Conn = (*dummyConn)(nil)
+
+type dummyConn struct {
+	rawConn *dummyRawConn
+}
+
+func (d *dummyConn) SyscallConn() (syscall.RawConn, error) {
+	return d.rawConn, nil
+}
+
+var errDummy = fmt.Errorf("dummyConn err")
+
+func (d *dummyConn) Read(b []byte) (n int, err error) {
+	return 0, errDummy
+}
+
+func (d *dummyConn) Write(b []byte) (n int, err error) {
+	return 0, errDummy
+}
+
+func (d *dummyConn) Close() error {
+	d.rawConn.Close()
+	return nil
+}
+
+func (d *dummyConn) LocalAddr() net.Addr {
+	return &net.TCPAddr{}
+}
+
+func (d *dummyConn) RemoteAddr() net.Addr {
+	return &net.TCPAddr{}
+}
+
+func (d *dummyConn) SetDeadline(t time.Time) error {
+	return nil
+}
+
+func (d *dummyConn) SetReadDeadline(t time.Time) error {
+	return nil
+}
+
+func (d *dummyConn) SetWriteDeadline(t time.Time) error {
+	return nil
+}
+
+var _ syscall.RawConn = (*dummyRawConn)(nil)
+
+type dummyRawConn struct {
+	closed bool
+	mux    sync.Mutex
+}
+
+func (d *dummyRawConn) Control(f func(fd uintptr)) error {
+	return nil
+}
+
+func (d *dummyRawConn) Read(f func(fd uintptr) (done bool)) error {
+	d.mux.Lock()
+	defer d.mux.Unlock()
+	if d.closed {
+		return fmt.Errorf("dummyRawConn closed")
+	}
+	return nil
+}
+
+func (d *dummyRawConn) Write(f func(fd uintptr) (done bool)) error {
+	return nil
+}
+func (d *dummyRawConn) Close() {
+	d.mux.Lock()
+	d.closed = true
+	d.mux.Unlock()
 }