feat: allow customization of proxy transport configuration

internal/config/proxy_server.go

@@ -1,13 +1,71 @@
 package config
 
+import "time"
+
 type ProxyServerConfig struct {
-	HTTP    HTTPConfig    `yaml:"http"`
-	Metrics MetricsConfig `yaml:"metrics"`
+	HTTP      HTTPConfig      `yaml:"http"`
+	Metrics   MetricsConfig   `yaml:"metrics"`
+	Transport TransportConfig `yaml:"transport"`
+	Dial      DialConfig      `yaml:"dial"`
+}
+
+// See https://pkg.go.dev/net/http#Transport
+type TransportConfig struct {
+	ForceAttemptHTTP2      InterpolatedBool      `yaml:"forceAttemptHTTP2"`
+	MaxIdleConns           InterpolatedInt       `yaml:"maxIdleConns"`
+	MaxIdleConnsPerHost    InterpolatedInt       `yaml:"maxIdleConnsPerHost"`
+	MaxConnsPerHost        InterpolatedInt       `yaml:"maxConnsPerHost"`
+	IdleConnTimeout        *InterpolatedDuration `yaml:"idleConnTimeout"`
+	TLSHandshakeTimeout    *InterpolatedDuration `yaml:"tlsHandshakeTimeout"`
+	ExpectContinueTimeout  *InterpolatedDuration `yaml:"expectContinueTimeout"`
+	DisableKeepAlives      InterpolatedBool      `yaml:"disableKeepAlives"`
+	DisableCompression     InterpolatedBool      `yaml:"disableCompression"`
+	ResponseHeaderTimeout  *InterpolatedDuration `yaml:"responseHeaderTimeout"`
+	WriteBufferSize        InterpolatedInt       `yaml:"writeBufferSize"`
+	ReadBufferSize         InterpolatedInt       `yaml:"readBufferSize"`
+	MaxResponseHeaderBytes InterpolatedInt       `yaml:"maxResponseHeaderBytes"`
 }
 
 func NewDefaultProxyServerConfig() ProxyServerConfig {
 	return ProxyServerConfig{
-		HTTP:    NewHTTPConfig("0.0.0.0", 8080),
-		Metrics: NewDefaultMetricsConfig(),
+		HTTP:      NewHTTPConfig("0.0.0.0", 8080),
+		Metrics:   NewDefaultMetricsConfig(),
+		Transport: NewDefaultTransportConfig(),
+		Dial:      NewDefaultDialConfig(),
+	}
+}
+
+// See https://pkg.go.dev/net#Dialer
+type DialConfig struct {
+	Timeout       *InterpolatedDuration `yaml:"timeout"`
+	KeepAlive     *InterpolatedDuration `yaml:"keepAlive"`
+	FallbackDelay *InterpolatedDuration `yaml:"fallbackDelay"`
+	DualStack     InterpolatedBool      `yaml:"dualStack"`
+}
+
+func NewDefaultDialConfig() DialConfig {
+	return DialConfig{
+		Timeout:       NewInterpolatedDuration(30 * time.Second),
+		KeepAlive:     NewInterpolatedDuration(30 * time.Second),
+		FallbackDelay: NewInterpolatedDuration(300 * time.Millisecond),
+		DualStack:     true,
+	}
+}
+
+func NewDefaultTransportConfig() TransportConfig {
+	return TransportConfig{
+		ForceAttemptHTTP2:      true,
+		MaxIdleConns:           100,
+		MaxIdleConnsPerHost:    100,
+		MaxConnsPerHost:        100,
+		IdleConnTimeout:        NewInterpolatedDuration(90 * time.Second),
+		TLSHandshakeTimeout:    NewInterpolatedDuration(10 * time.Second),
+		ExpectContinueTimeout:  NewInterpolatedDuration(1 * time.Second),
+		ResponseHeaderTimeout:  NewInterpolatedDuration(10 * time.Second),
+		DisableCompression:     false,
+		DisableKeepAlives:      false,
+		ReadBufferSize:         4096,
+		WriteBufferSize:        4096,
+		MaxResponseHeaderBytes: 0,
 	}
 }

internal/proxy/server.go

@@ -6,6 +6,9 @@ import (
 	"log"
 	"net"
 	"net/http"
+	"net/http/httputil"
+	"net/url"
+	"time"
 
 	"forge.cadoles.com/Cadoles/go-proxy"
 	bouncerChi "forge.cadoles.com/cadoles/bouncer/internal/chi"
@@ -115,6 +118,7 @@ func (s *Server) run(parentCtx context.Context, addrs chan net.Addr, errs chan e
 			proxy.WithResponseTransformers(
 				director.ResponseTransformer(),
 			),
+			proxy.WithReverseProxyFactory(s.createReverseProxy),
 		)
 
 		r.Handle("/*", handler)
@@ -127,6 +131,49 @@ func (s *Server) run(parentCtx context.Context, addrs chan net.Addr, errs chan e
 	logger.Info(ctx, "http server exiting")
 }
 
+func (s *Server) createReverseProxy(ctx context.Context, target *url.URL) *httputil.ReverseProxy {
+	reverseProxy := httputil.NewSingleHostReverseProxy(target)
+
+	dialConfig := s.serverConfig.Dial
+
+	dialer := &net.Dialer{
+		Timeout:       time.Duration(*dialConfig.Timeout),
+		KeepAlive:     time.Duration(*dialConfig.KeepAlive),
+		FallbackDelay: time.Duration(*dialConfig.FallbackDelay),
+		DualStack:     bool(dialConfig.DualStack),
+	}
+
+	transportConfig := s.serverConfig.Transport
+
+	reverseProxy.Transport = &http.Transport{
+		Proxy:                  http.ProxyFromEnvironment,
+		DialContext:            dialer.DialContext,
+		ForceAttemptHTTP2:      bool(transportConfig.ForceAttemptHTTP2),
+		MaxIdleConns:           int(transportConfig.MaxIdleConns),
+		MaxIdleConnsPerHost:    int(transportConfig.MaxIdleConnsPerHost),
+		MaxConnsPerHost:        int(transportConfig.MaxConnsPerHost),
+		IdleConnTimeout:        time.Duration(*transportConfig.IdleConnTimeout),
+		TLSHandshakeTimeout:    time.Duration(*transportConfig.TLSHandshakeTimeout),
+		ExpectContinueTimeout:  time.Duration(*transportConfig.ExpectContinueTimeout),
+		DisableKeepAlives:      bool(transportConfig.DisableKeepAlives),
+		DisableCompression:     bool(transportConfig.DisableCompression),
+		ResponseHeaderTimeout:  time.Duration(*transportConfig.ResponseHeaderTimeout),
+		WriteBufferSize:        int(transportConfig.WriteBufferSize),
+		ReadBufferSize:         int(transportConfig.ReadBufferSize),
+		MaxResponseHeaderBytes: int64(transportConfig.MaxResponseHeaderBytes),
+	}
+
+	reverseProxy.ErrorHandler = s.errorHandler
+
+	return reverseProxy
+}
+
+func (s *Server) errorHandler(w http.ResponseWriter, r *http.Request, err error) {
+	logger.Error(r.Context(), "proxy error", logger.E(errors.WithStack(err)))
+
+	http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+}
+
 func NewServer(funcs ...OptionFunc) *Server {
 	opt := defaultOption()
 	for _, fn := range funcs {