refactor: fix incorrect logic introduced in previous commits and improve error handling

internal/net/gphttp/loadbalancer/ip_hash.go

@@ -3,6 +3,7 @@ package loadbalancer
 import (
 	"net"
 	"net/http"
+	"slices"
 	"sync"
 
 	"github.com/bytedance/gopkg/util/xxhash3"
@@ -39,16 +40,6 @@ func (impl *ipHash) OnAddServer(srv types.LoadBalancerServer) {
 	impl.mu.Lock()
 	defer impl.mu.Unlock()
 
-	for i, s := range impl.pool {
-		if s == srv {
-			return
-		}
-		if s == nil {
-			impl.pool[i] = srv
-			return
-		}
-	}
-
 	impl.pool = append(impl.pool, srv)
 }
 
@@ -58,27 +49,33 @@ func (impl *ipHash) OnRemoveServer(srv types.LoadBalancerServer) {
 
 	for i, s := range impl.pool {
 		if s == srv {
-			impl.pool[i] = nil
+			impl.pool = slices.Delete(impl.pool, i, 1)
 			return
 		}
 	}
 }
 
 func (impl *ipHash) ServeHTTP(_ types.LoadBalancerServers, rw http.ResponseWriter, r *http.Request) {
+	if impl.realIP != nil {
+		// resolve real client IP
+		if proceed := impl.realIP.TryModifyRequest(rw, r); !proceed {
+			return
+		}
+	}
+
 	srv := impl.ChooseServer(impl.pool, r)
 	if srv == nil || srv.Status().Bad() {
 		http.Error(rw, "Service unavailable", http.StatusServiceUnavailable)
 		return
 	}
 
-	if impl.realIP != nil {
-		impl.realIP.ModifyRequest(srv.ServeHTTP, rw, r)
-	} else {
-		srv.ServeHTTP(rw, r)
-	}
+	srv.ServeHTTP(rw, r)
 }
 
 func (impl *ipHash) ChooseServer(_ types.LoadBalancerServers, r *http.Request) types.LoadBalancerServer {
+	impl.mu.Lock()
+	defer impl.mu.Unlock()
+
 	if len(impl.pool) == 0 {
 		return nil
 	}

internal/net/gphttp/loadbalancer/least_conn.go

@@ -46,8 +46,8 @@ func (impl *leastConn) ServeHTTP(srvs types.LoadBalancerServers, rw http.Respons
 	}
 
 	minConn.Add(1)
+	defer minConn.Add(-1)
 	srv.ServeHTTP(rw, r)
-	minConn.Add(-1)
 }
 
 func (impl *leastConn) ChooseServer(srvs types.LoadBalancerServers, r *http.Request) types.LoadBalancerServer {
@@ -55,18 +55,15 @@ func (impl *leastConn) ChooseServer(srvs types.LoadBalancerServers, r *http.Requ
 		return nil
 	}
 
-	srv := srvs[0]
-	minConn, ok := impl.nConn.Load(srv)
-	if !ok {
-		return nil
-	}
+	var srv types.LoadBalancerServer
+	var minConn *atomic.Int64
 
-	for i := 1; i < len(srvs); i++ {
+	for i := range srvs {
 		nConn, ok := impl.nConn.Load(srvs[i])
 		if !ok {
 			continue
 		}
-		if nConn.Load() < minConn.Load() {
+		if minConn == nil || nConn.Load() < minConn.Load() {
 			minConn = nConn
 			srv = srvs[i]
 		}

internal/net/gphttp/loadbalancer/loadbalancer.go

@@ -364,11 +364,5 @@ func isIdlewatcherRequest(r *http.Request) bool {
 		return true
 	}
 
-	// Check if this is a page refresh after idlewatcher wake up
-	// by looking for the sticky session cookie
-	if _, err := r.Cookie("godoxy_lb_sticky"); err == nil {
-		return true
-	}
-
 	return false
 }

internal/net/gphttp/loadbalancer/round_robin.go

@@ -21,9 +21,6 @@ func (lb *roundRobin) ChooseServer(srvs types.LoadBalancerServers, r *http.Reque
 	if len(srvs) == 0 {
 		return nil
 	}
-	index := lb.index.Add(1) % uint32(len(srvs))
-	if lb.index.Load() >= 2*uint32(len(srvs)) {
-		lb.index.Store(0)
-	}
+	index := (lb.index.Add(1) - 1) % uint32(len(srvs))
 	return srvs[index]
 }

internal/net/gphttp/loadbalancer/sticky.go

@@ -3,6 +3,7 @@ package loadbalancer
 import (
 	"encoding/hex"
 	"net/http"
+	"strings"
 	"time"
 	"unsafe"
 
@@ -46,5 +47,5 @@ func setStickyCookie(rw http.ResponseWriter, r *http.Request, srv types.LoadBala
 }
 
 func isSecure(r *http.Request) bool {
-	return r.TLS != nil || r.Header.Get("X-Forwarded-Proto") == "https"
+	return r.TLS != nil || strings.EqualFold(r.Header.Get("X-Forwarded-Proto"), "https")
 }

internal/net/gphttp/middleware/middleware.go

@@ -170,6 +170,13 @@ func (m *Middleware) ModifyRequest(next http.HandlerFunc, w http.ResponseWriter,
 	next(w, r)
 }
 
+func (m *Middleware) TryModifyRequest(w http.ResponseWriter, r *http.Request) (proceed bool) {
+	if exec, ok := m.impl.(RequestModifier); ok {
+		return exec.before(w, r)
+	}
+	return true
+}
+
 func (m *Middleware) ModifyResponse(resp *http.Response) error {
 	if exec, ok := m.impl.(ResponseModifier); ok {
 		return exec.modifyResponse(resp)