feat: add OpenAI image generation controls

backend/internal/config/config.go

@@ -575,6 +575,24 @@ type ConcurrencyConfig struct {
 	PingInterval int `mapstructure:"ping_interval"`
 }
 
+type ImageConcurrencyConfig struct {
+	// Enabled: 是否启用图片生成独立并发限制，默认关闭以保持现有行为
+	Enabled bool `mapstructure:"enabled"`
+	// MaxConcurrentRequests: 当前进程允许同时处理的图片生成请求数，0表示不限制
+	MaxConcurrentRequests int `mapstructure:"max_concurrent_requests"`
+	// OverflowMode: 图片并发达到上限后的处理方式：reject/wait
+	OverflowMode string `mapstructure:"overflow_mode"`
+	// WaitTimeoutSeconds: overflow_mode=wait 时等待图片并发槽位的超时时间（秒）
+	WaitTimeoutSeconds int `mapstructure:"wait_timeout_seconds"`
+	// MaxWaitingRequests: overflow_mode=wait 时当前进程允许排队等待的图片请求数
+	MaxWaitingRequests int `mapstructure:"max_waiting_requests"`
+}
+
+const (
+	ImageConcurrencyOverflowModeReject = "reject"
+	ImageConcurrencyOverflowModeWait   = "wait"
+)
+
 // GatewayConfig API网关相关配置
 type GatewayConfig struct {
 	// 等待上游响应头的超时时间（秒），0表示无超时
@@ -604,6 +622,8 @@ type GatewayConfig struct {
 	OpenAIPassthroughAllowTimeoutHeaders bool `mapstructure:"openai_passthrough_allow_timeout_headers"`
 	// OpenAIWS: OpenAI Responses WebSocket 配置（默认开启，可按需回滚到 HTTP）
 	OpenAIWS GatewayOpenAIWSConfig `mapstructure:"openai_ws"`
+	// ImageConcurrency: 图片生成独立并发限制配置（默认关闭）
+	ImageConcurrency ImageConcurrencyConfig `mapstructure:"image_concurrency"`
 
 	// HTTP 上游连接池配置（性能优化：支持高并发场景调优）
 	// MaxIdleConns: 所有主机的最大空闲连接总数
@@ -635,6 +655,10 @@ type GatewayConfig struct {
 	StreamDataIntervalTimeout int `mapstructure:"stream_data_interval_timeout"`
 	// StreamKeepaliveInterval: 流式 keepalive 间隔（秒），0表示禁用
 	StreamKeepaliveInterval int `mapstructure:"stream_keepalive_interval"`
+	// ImageStreamDataIntervalTimeout: 图片流数据间隔超时（秒），0表示禁用
+	ImageStreamDataIntervalTimeout int `mapstructure:"image_stream_data_interval_timeout"`
+	// ImageStreamKeepaliveInterval: 图片流式 keepalive 间隔（秒），0表示禁用
+	ImageStreamKeepaliveInterval int `mapstructure:"image_stream_keepalive_interval"`
 	// MaxLineSize: 上游 SSE 单行最大字节数（0使用默认值）
 	MaxLineSize int `mapstructure:"max_line_size"`
 
@@ -1672,6 +1696,11 @@ func setDefaults() {
 	viper.SetDefault("gateway.openai_ws.scheduler_score_weights.queue", 0.7)
 	viper.SetDefault("gateway.openai_ws.scheduler_score_weights.error_rate", 0.8)
 	viper.SetDefault("gateway.openai_ws.scheduler_score_weights.ttft", 0.5)
+	viper.SetDefault("gateway.image_concurrency.enabled", false)
+	viper.SetDefault("gateway.image_concurrency.max_concurrent_requests", 0)
+	viper.SetDefault("gateway.image_concurrency.overflow_mode", ImageConcurrencyOverflowModeReject)
+	viper.SetDefault("gateway.image_concurrency.wait_timeout_seconds", 30)
+	viper.SetDefault("gateway.image_concurrency.max_waiting_requests", 100)
 	viper.SetDefault("gateway.antigravity_fallback_cooldown_minutes", 1)
 	viper.SetDefault("gateway.antigravity_extra_retries", 10)
 	viper.SetDefault("gateway.max_body_size", int64(256*1024*1024))
@@ -1689,6 +1718,8 @@ func setDefaults() {
 	viper.SetDefault("gateway.concurrency_slot_ttl_minutes", 30) // 并发槽位过期时间（支持超长请求）
 	viper.SetDefault("gateway.stream_data_interval_timeout", 180)
 	viper.SetDefault("gateway.stream_keepalive_interval", 10)
+	viper.SetDefault("gateway.image_stream_data_interval_timeout", 900)
+	viper.SetDefault("gateway.image_stream_keepalive_interval", 10)
 	viper.SetDefault("gateway.max_line_size", 500*1024*1024)
 	viper.SetDefault("gateway.scheduling.sticky_session_max_waiting", 3)
 	viper.SetDefault("gateway.scheduling.sticky_session_wait_timeout", 120*time.Second)
@@ -2239,6 +2270,21 @@ func (c *Config) Validate() error {
 				ConnectionPoolIsolationProxy, ConnectionPoolIsolationAccount, ConnectionPoolIsolationAccountProxy)
 		}
 	}
+	if c.Gateway.ImageConcurrency.MaxConcurrentRequests < 0 {
+		return fmt.Errorf("gateway.image_concurrency.max_concurrent_requests must be non-negative")
+	}
+	switch strings.TrimSpace(c.Gateway.ImageConcurrency.OverflowMode) {
+	case "", ImageConcurrencyOverflowModeReject, ImageConcurrencyOverflowModeWait:
+	default:
+		return fmt.Errorf("gateway.image_concurrency.overflow_mode must be one of: %s/%s",
+			ImageConcurrencyOverflowModeReject, ImageConcurrencyOverflowModeWait)
+	}
+	if c.Gateway.ImageConcurrency.WaitTimeoutSeconds < 0 {
+		return fmt.Errorf("gateway.image_concurrency.wait_timeout_seconds must be non-negative")
+	}
+	if c.Gateway.ImageConcurrency.MaxWaitingRequests < 0 {
+		return fmt.Errorf("gateway.image_concurrency.max_waiting_requests must be non-negative")
+	}
 	if c.Gateway.MaxIdleConns <= 0 {
 		return fmt.Errorf("gateway.max_idle_conns must be positive")
 	}
@@ -2277,6 +2323,20 @@ func (c *Config) Validate() error {
 		(c.Gateway.StreamKeepaliveInterval < 5 || c.Gateway.StreamKeepaliveInterval > 30) {
 		return fmt.Errorf("gateway.stream_keepalive_interval must be 0 or between 5-30 seconds")
 	}
+	if c.Gateway.ImageStreamDataIntervalTimeout < 0 {
+		return fmt.Errorf("gateway.image_stream_data_interval_timeout must be non-negative")
+	}
+	if c.Gateway.ImageStreamDataIntervalTimeout != 0 &&
+		(c.Gateway.ImageStreamDataIntervalTimeout < 60 || c.Gateway.ImageStreamDataIntervalTimeout > 1800) {
+		return fmt.Errorf("gateway.image_stream_data_interval_timeout must be 0 or between 60-1800 seconds")
+	}
+	if c.Gateway.ImageStreamKeepaliveInterval < 0 {
+		return fmt.Errorf("gateway.image_stream_keepalive_interval must be non-negative")
+	}
+	if c.Gateway.ImageStreamKeepaliveInterval != 0 &&
+		(c.Gateway.ImageStreamKeepaliveInterval < 5 || c.Gateway.ImageStreamKeepaliveInterval > 60) {
+		return fmt.Errorf("gateway.image_stream_keepalive_interval must be 0 or between 5-60 seconds")
+	}
 	// 兼容旧键 sticky_previous_response_ttl_seconds
 	if c.Gateway.OpenAIWS.StickyResponseIDTTLSeconds <= 0 && c.Gateway.OpenAIWS.StickyPreviousResponseTTLSeconds > 0 {
 		c.Gateway.OpenAIWS.StickyResponseIDTTLSeconds = c.Gateway.OpenAIWS.StickyPreviousResponseTTLSeconds