perf: add HTTP connection pooling across providers and disable proxy buffering on SSE streams

internal/providers/deepseek.go

@@ -22,7 +22,7 @@ type DeepSeekProvider struct {
 
 func NewDeepSeekProvider(cfg config.DeepSeekConfig, apiKey string) *DeepSeekProvider {
 	return &DeepSeekProvider{
-		client: resty.New().SetTimeout(10 * time.Minute),
+		client: NewOptimizedRestyClient(10 * time.Minute),
 		config: cfg,
 		apiKey: apiKey,
 	}

internal/providers/gemini.go

@@ -21,7 +21,7 @@ type GeminiProvider struct {
 
 func NewGeminiProvider(cfg config.GeminiConfig, apiKey string) *GeminiProvider {
 	return &GeminiProvider{
-		client: resty.New().SetTimeout(10 * time.Minute),
+		client: NewOptimizedRestyClient(10 * time.Minute),
 		config: cfg,
 		apiKey: apiKey,
 	}

internal/providers/grok.go

@@ -20,7 +20,7 @@ type GrokProvider struct {
 
 func NewGrokProvider(cfg config.GrokConfig, apiKey string) *GrokProvider {
 	return &GrokProvider{
-		client: resty.New().SetTimeout(10 * time.Minute),
+		client: NewOptimizedRestyClient(10 * time.Minute),
 		config: cfg,
 		apiKey: apiKey,
 	}

internal/providers/helpers.go

@@ -5,10 +5,15 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"net"
+	"net/http"
 	"regexp"
 	"strings"
+	"time"
 
 	"gophergate/internal/models"
+
+	"github.com/go-resty/resty/v2"
 )
 
 var keySanitizeRegex = regexp.MustCompile(`(?i)(key|api_key|secret)=[^&]+`)
@@ -18,6 +23,34 @@ func SanitizeURL(rawURL string) string {
 	return keySanitizeRegex.ReplaceAllString(rawURL, "$1=REDACTED")
 }
 
+// Shared HTTP transport configured with high connection pooling, TCP keep-alive,
+// and HTTP/2 multiplexing to minimize latency when connecting to upstream LLM providers.
+var sharedHTTPTransport = &http.Transport{
+	Proxy: http.ProxyFromEnvironment,
+	DialContext: (&net.Dialer{
+		Timeout:   30 * time.Second,
+		KeepAlive: 30 * time.Second,
+	}).DialContext,
+	ForceAttemptHTTP2:     true,
+	MaxIdleConns:          200,
+	MaxIdleConnsPerHost:   50,
+	IdleConnTimeout:       90 * time.Second,
+	TLSHandshakeTimeout:   10 * time.Second,
+	ExpectContinueTimeout: 1 * time.Second,
+}
+
+// NewOptimizedRestyClient creates a resty client equipped with HTTP connection pooling.
+func NewOptimizedRestyClient(timeout time.Duration) *resty.Client {
+	httpClient := &http.Client{
+		Transport: sharedHTTPTransport,
+	}
+	client := resty.NewWithClient(httpClient)
+	if timeout > 0 {
+		client.SetTimeout(timeout)
+	}
+	return client
+}
+
 
 func sanitizeFunctionName(name string) string {
 	var sb strings.Builder

internal/providers/moonshot.go

@@ -21,7 +21,7 @@ type MoonshotProvider struct {
 
 func NewMoonshotProvider(cfg config.MoonshotConfig, apiKey string) *MoonshotProvider {
 	return &MoonshotProvider{
-		client: resty.New().SetTimeout(10 * time.Minute),
+		client: NewOptimizedRestyClient(10 * time.Minute),
 		config: cfg,
 		apiKey: strings.TrimSpace(apiKey),
 	}

internal/providers/ollama.go

@@ -20,10 +20,9 @@ type OllamaProvider struct {
 }
 
 func NewOllamaProvider(cfg config.OllamaConfig) *OllamaProvider {
-	client := resty.New()
+	client := NewOptimizedRestyClient(15 * time.Minute)
 	// Set reasonable timeouts for local Ollama server (longer for larger models)
 	// For streaming, we want a very long timeout or none at all to handle generation time
-	client.SetTimeout(15 * time.Minute)
 	client.SetRetryCount(2)
 	client.SetRetryWaitTime(1 * time.Second)
 

internal/providers/openai.go

@@ -22,7 +22,7 @@ type OpenAIProvider struct {
 
 func NewOpenAIProvider(cfg config.OpenAIConfig, apiKey string) *OpenAIProvider {
 	return &OpenAIProvider{
-		client: resty.New().SetTimeout(10 * time.Minute),
+		client: NewOptimizedRestyClient(10 * time.Minute),
 		config: cfg,
 		apiKey: apiKey,
 	}

internal/providers/xiaomi.go

@@ -21,7 +21,7 @@ type XiaomiProvider struct {
 
 func NewXiaomiProvider(cfg config.XiaomiConfig, apiKey string) *XiaomiProvider {
 	return &XiaomiProvider{
-		client: resty.New().SetTimeout(10 * time.Minute),
+		client: NewOptimizedRestyClient(10 * time.Minute),
 		config: cfg,
 		apiKey: strings.TrimSpace(apiKey),
 	}

internal/server/server.go

@@ -403,6 +403,7 @@ func (s *Server) handleResponses(c *gin.Context) {
 		c.Header("Content-Type", "text/event-stream")
 		c.Header("Cache-Control", "no-cache")
 		c.Header("Connection", "keep-alive")
+		c.Header("X-Accel-Buffering", "no")
 
 		var lastUsage *models.ResponsesUsage
 		c.Stream(func(w io.Writer) bool {
@@ -765,6 +766,7 @@ func (s *Server) handleChatCompletions(c *gin.Context) {
 		c.Header("Content-Type", "text/event-stream")
 		c.Header("Cache-Control", "no-cache")
 		c.Header("Connection", "keep-alive")
+		c.Header("X-Accel-Buffering", "no")
 
 		var lastUsage *models.Usage
 		c.Stream(func(w io.Writer) bool {