Use SO_REUSEADDR and SO_REUSEPORT options when creating the sql server on Unix

server/listener.go

@@ -53,7 +53,7 @@ type Listener struct {
 // For unix socket connection, 'unixSocketPath' takes a path for the unix socket file.
 // If 'unixSocketPath' is empty, no need to create the second listener.
 func NewListener(protocol, address string, unixSocketPath string) (*Listener, error) {
-	netl, err := net.Listen(protocol, address)
+	netl, err := newNetListener(protocol, address)
 	if err != nil {
 		return nil, err
 	}

server/net_listener_unix.go

@@ -0,0 +1,39 @@
+//go:build !windows
+
+package server
+
+import (
+	"context"
+	"net"
+	"syscall"
+
+	"golang.org/x/sys/unix"
+)
+
+// Very rarely in our CI, the server fails to bind to the port with the error: "port already in use."
+// This is odd because the server already confirms that the port is not in use before connecting.
+// Using the SO_REUSEADDR and SO_REUSEPORT options prevents this spurious failure.
+// This is safe to do because we have already checked that the
+func newNetListener(protocol, address string) (net.Listener, error) {
+	lc := net.ListenConfig{
+		Control: func(network, address string, c syscall.RawConn) error {
+			var socketErr error
+			err := c.Control(func(fd uintptr) {
+				err := unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_REUSEADDR, 1)
+				if err != nil {
+					socketErr = err
+				}
+
+				err = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_REUSEPORT, 1)
+				if err != nil {
+					socketErr = err
+				}
+			})
+			if err != nil {
+				return err
+			}
+			return socketErr
+		},
+	}
+	return lc.Listen(context.Background(), protocol, address)
+}

server/net_listener_windows.go

@@ -0,0 +1,7 @@
+package server
+
+import "net"
+
+func newNetListener(protocol, address string) (net.Listener, error) {
+	return net.Listen(protocol, address)
+}

server/server.go

@@ -16,6 +16,8 @@ package server
 
 import (
 	"errors"
+	"fmt"
+	"net"
 	"time"
 
 	"github.com/dolthub/vitess/go/mysql"
@@ -97,6 +99,16 @@ func NewValidatingServer(
 	return newServerFromHandler(cfg, e, sm, handler)
 }
 
+func portInUse(hostPort string) bool {
+	timeout := time.Second
+	conn, _ := net.DialTimeout("tcp", hostPort, timeout)
+	if conn != nil {
+		defer conn.Close()
+		return true
+	}
+	return false
+}
+
 func newServerFromHandler(cfg Config, e *sqle.Engine, sm *SessionManager, handler mysql.Handler) (*Server, error) {
 	if cfg.ConnReadTimeout < 0 {
 		cfg.ConnReadTimeout = 0
@@ -109,6 +121,11 @@ func newServerFromHandler(cfg Config, e *sqle.Engine, sm *SessionManager, handle
 	}
 
 	var unixSocketInUse error
+
+	if portInUse(cfg.Address) {
+		unixSocketInUse = fmt.Errorf("Port %s already in use.", cfg.Address)
+	}
+
 	l, err := NewListener(cfg.Protocol, cfg.Address, cfg.Socket)
 	if err != nil {
 		if errors.Is(err, UnixSocketInUseError) {