Feature: add tolerance for url-test

README.md

@@ -293,6 +293,7 @@ proxy-groups:
       - ss1
       - ss2
       - vmess1
+    # tolerance: 150
     url: 'http://www.gstatic.com/generate_204'
     interval: 300
 

adapters/outboundgroup/parser.go

@@ -101,7 +101,8 @@ func ParseProxyGroup(config map[string]interface{}, proxyMap map[string]C.Proxy,
 	var group C.ProxyAdapter
 	switch groupOption.Type {
 	case "url-test":
-		group = NewURLTest(groupName, providers)
+		opts := parseURLTestOption(config)
+		group = NewURLTest(groupName, providers, opts...)
 	case "select":
 		group = NewSelector(groupName, providers)
 	case "fallback":

adapters/outboundgroup/urltest.go

@@ -11,8 +11,19 @@ import (
 	C "github.com/Dreamacro/clash/constant"
 )
 
+type urlTestOption func(*URLTest)
+
+func urlTestWithTolerance(tolerance uint16) urlTestOption {
+	return func(u *URLTest) {
+		u.tolerance = tolerance
+	}
+}
+
 type URLTest struct {
 	*outbound.Base
+	tolerance  uint16
+	lastDelay  uint16
+	fastNode   C.Proxy
 	single     *singledo.Single
 	fastSingle *singledo.Single
 	providers  []provider.ProxyProvider
@@ -52,6 +63,13 @@ func (u *URLTest) proxies() []C.Proxy {
 
 func (u *URLTest) fast() C.Proxy {
 	elm, _, _ := u.fastSingle.Do(func() (interface{}, error) {
+		// tolerance
+		if u.tolerance != 0 && u.fastNode != nil {
+			if u.fastNode.LastDelay() < u.lastDelay+u.tolerance {
+				return u.fastNode, nil
+			}
+		}
+
 		proxies := u.proxies()
 		fast := proxies[0]
 		min := fast.LastDelay()
@@ -66,6 +84,9 @@ func (u *URLTest) fast() C.Proxy {
 				min = delay
 			}
 		}
+
+		u.fastNode = fast
+		u.lastDelay = fast.LastDelay()
 		return fast, nil
 	})
 
@@ -88,11 +109,30 @@ func (u *URLTest) MarshalJSON() ([]byte, error) {
 	})
 }
 
-func NewURLTest(name string, providers []provider.ProxyProvider) *URLTest {
-	return &URLTest{
+func parseURLTestOption(config map[string]interface{}) []urlTestOption {
+	opts := []urlTestOption{}
+
+	// tolerance
+	if elm, ok := config["tolerance"]; ok {
+		if tolerance, ok := elm.(int); ok {
+			opts = append(opts, urlTestWithTolerance(uint16(tolerance)))
+		}
+	}
+
+	return opts
+}
+
+func NewURLTest(name string, providers []provider.ProxyProvider, options ...urlTestOption) *URLTest {
+	urlTest := &URLTest{
 		Base:       outbound.NewBase(name, "", C.URLTest, false),
 		single:     singledo.NewSingle(defaultGetProxiesDuration),
 		fastSingle: singledo.NewSingle(time.Second * 10),
 		providers:  providers,
 	}
+
+	for _, option := range options {
+		option(urlTest)
+	}
+
+	return urlTest
 }