server: Get rid of globals for setting a protocol listener factory. Get rid of unused, global-ridden and complicated Interceptor and Option functionality.

server/extension.go

@@ -27,24 +27,36 @@ import (
 	sqle "github.com/dolthub/go-mysql-server"
 )
 
-func Intercept(h Interceptor) {
-	inters = append(inters, h)
-	sort.Slice(inters, func(i, j int) bool { return inters[i].Priority() < inters[j].Priority() })
-}
-
-func WithChain() Option {
-	return func(e *sqle.Engine, sm *SessionManager, handler mysql.Handler) {
-		f := DefaultProtocolListenerFunc
-		DefaultProtocolListenerFunc = func(cfg mysql.ListenerConfig, sel ServerEventListener) (ProtocolListener, error) {
-			cfg.Handler = buildChain(cfg.Handler)
-			return f(cfg, sel)
-		}
-	}
+// InterceptorChain allows an integrator to build a chain of
+// |Interceptor| instances which will wrap and intercept the server's
+// mysql.Handler.
+//
+// Example usage:
+//
+// var ic InterceptorChain
+// ic.WithInterceptor(metricsInterceptor)
+// ic.WithInterceptor(authInterceptor)
+// server, err := NewServer(Config{ ..., Options: []Option{ic.Option()}, ...}, ...)
+type InterceptorChain struct {
+	inters []Interceptor
 }
 
-var inters []Interceptor
+func (ic *InterceptorChain) WithInterceptor(h Interceptor) {
+	ic.inters = append(ic.inters, h)
+}
 
-func buildChain(h mysql.Handler) mysql.Handler {
+func (ic *InterceptorChain) Option() Option {
+	return func(e *sqle.Engine, sm *SessionManager, handler mysql.Handler) (*sqle.Engine, *SessionManager, mysql.Handler) {
+		chainHandler := buildChain(handler, ic.inters)
+		return e, sm, chainHandler
+	}
+}
+
+func buildChain(h mysql.Handler, inters []Interceptor) mysql.Handler {
+	// XXX: Mutates |inters|
+	sort.Slice(inters, func(i, j int) bool {
+		return inters[i].Priority() < inters[j].Priority()
+	})
 	var last Chain = h
 	for i := len(inters) - 1; i >= 0; i-- {
 		filter := inters[i]
@@ -55,7 +67,6 @@ func buildChain(h mysql.Handler) mysql.Handler {
 }
 
 type Interceptor interface {
-
 	// Priority returns the priority of the interceptor.
 	Priority() int
 
@@ -88,7 +99,6 @@ type Interceptor interface {
 }
 
 type Chain interface {
-
 	// ComQuery is called when a connection receives a query.
 	// Note the contents of the query slice may change after
 	// the first call to callback. So the Handler should not

server/server.go

@@ -37,14 +37,19 @@ type ProtocolListener interface {
 }
 
 // ProtocolListenerFunc returns a ProtocolListener based on the configuration it was given.
-type ProtocolListenerFunc func(cfg mysql.ListenerConfig, sel ServerEventListener) (ProtocolListener, error)
-
-// DefaultProtocolListenerFunc is the protocol listener, which defaults to Vitess' protocol listener. Changing
-// this function will change the protocol listener used when creating all servers. If multiple servers are needed
-// with different protocols, then create each server after changing this function. Servers retain the protocol that
-// they were created with.
-var DefaultProtocolListenerFunc ProtocolListenerFunc = func(cfg mysql.ListenerConfig, sel ServerEventListener) (ProtocolListener, error) {
-	return mysql.NewListenerWithConfig(cfg)
+type ProtocolListenerFunc func(cfg Config, listenerCfg mysql.ListenerConfig, sel ServerEventListener) (ProtocolListener, error)
+
+func MySQLProtocolListenerFactory(cfg Config, listenerCfg mysql.ListenerConfig, sel ServerEventListener) (ProtocolListener, error) {
+	vtListener, err := mysql.NewListenerWithConfig(listenerCfg)
+	if err != nil {
+		return nil, err
+	}
+	if cfg.Version != "" {
+		vtListener.ServerVersion = cfg.Version
+	}
+	vtListener.TLSConfig = cfg.TLSConfig
+	vtListener.RequireSecureTransport = cfg.RequireSecureTransport
+	return vtListener, nil
 }
 
 type ServerEventListener interface {
@@ -114,10 +119,6 @@ func portInUse(hostPort string) bool {
 }
 
 func newServerFromHandler(cfg Config, e *sqle.Engine, sm *SessionManager, handler mysql.Handler, sel ServerEventListener) (*Server, error) {
-	for _, option := range cfg.Options {
-		option(e, sm, handler)
-	}
-
 	if cfg.ConnReadTimeout < 0 {
 		cfg.ConnReadTimeout = 0
 	}
@@ -128,6 +129,10 @@ func newServerFromHandler(cfg Config, e *sqle.Engine, sm *SessionManager, handle
 		cfg.MaxConnections = 0
 	}
 
+	for _, opt := range cfg.Options {
+		e, sm, handler = opt(e, sm, handler)
+	}
+
 	l := cfg.Listener
 	var unixSocketInUse error
 	if l == nil {
@@ -156,19 +161,15 @@ func newServerFromHandler(cfg Config, e *sqle.Engine, sm *SessionManager, handle
 		ConnReadBufferSize:       mysql.DefaultConnBufferSize,
 		AllowClearTextWithoutTLS: cfg.AllowClearTextWithoutTLS,
 	}
-	protocolListener, err := DefaultProtocolListenerFunc(listenerCfg, sel)
+	plf := cfg.ProtocolListenerFactory
+	if plf == nil {
+		plf = MySQLProtocolListenerFactory
+	}
+	protocolListener, err := plf(cfg, listenerCfg, sel)
 	if err != nil {
 		return nil, err
 	}
 
-	if vtListener, ok := protocolListener.(*mysql.Listener); ok {
-		if cfg.Version != "" {
-			vtListener.ServerVersion = cfg.Version
-		}
-		vtListener.TLSConfig = cfg.TLSConfig
-		vtListener.RequireSecureTransport = cfg.RequireSecureTransport
-	}
-
 	return &Server{
 		Listener:   protocolListener,
 		handler:    handler,

server/server_config.go

@@ -23,13 +23,9 @@ import (
 	"go.opentelemetry.io/otel/trace"
 
 	gms "github.com/dolthub/go-mysql-server"
-	sqle "github.com/dolthub/go-mysql-server"
 	"github.com/dolthub/go-mysql-server/sql"
 )
 
-// Option is an option to customize server.
-type Option func(e *sqle.Engine, sm *SessionManager, handler mysql.Handler)
-
 // Server is a MySQL server for SQLe engines.
 type Server struct {
 	Listener   ProtocolListener
@@ -38,6 +34,9 @@ type Server struct {
 	Engine     *gms.Engine
 }
 
+// An option to customize the server.
+type Option func(e *gms.Engine, sm *SessionManager, handler mysql.Handler) (*gms.Engine, *SessionManager, mysql.Handler)
+
 // Config for the mysql server.
 type Config struct {
 	// Protocol for the connection.
@@ -82,8 +81,14 @@ type Config struct {
 	// If true, queries will be logged as base64 encoded strings.
 	// If false (default behavior), queries will be logged as strings, but newlines and tabs will be replaced with spaces.
 	EncodeLoggedQuery bool
-	// Options add additional options to customize the server.
+	// Options gets a chance to visit and mutate the GMS *Engine,
+	// *server.SessionManager and the mysql.Handler as the server
+	// is being initialized, before the ProtocolListener is
+	// constructed.
 	Options []Option
+	// Used to get the ProtocolListener on server start.
+	// If unset, defaults to MySQLProtocolListenerFactory.
+	ProtocolListenerFactory ProtocolListenerFunc
 }
 
 func (c Config) NewConfig() (Config, error) {