feat(网关): 集成运维监控到 API 网关处理器

- 在 gateway_handler 中添加请求监控和错误追踪
- 在 openai_gateway_handler 中集成 ops 指标采集
- 在 gemini_v1beta_handler 中集成 ops 指标采集
- 更新 handler 基类支持 ops 错误日志记录

backend/internal/handler/openai_gateway_handler.go

@@ -75,6 +75,8 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 		return
 	}
 
+	setOpsRequestContext(c, "", false, body)
+
 	// Parse request body to map for potential modification
 	var reqBody map[string]any
 	if err := json.Unmarshal(body, &reqBody); err != nil {
@@ -104,6 +106,8 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 		}
 	}
 
+	setOpsRequestContext(c, reqModel, reqStream, body)
+
 	// Track if we've started streaming (for error handling)
 	streamStarted := false
 
@@ -113,6 +117,7 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 	// 0. Check if wait queue is full
 	maxWait := service.CalculateMaxWait(subject.Concurrency)
 	canWait, err := h.concurrencyHelper.IncrementWaitCount(c.Request.Context(), subject.UserID, maxWait)
+	waitCounted := false
 	if err != nil {
 		log.Printf("Increment wait count failed: %v", err)
 		// On error, allow request to proceed
@@ -120,8 +125,14 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 		h.errorResponse(c, http.StatusTooManyRequests, "rate_limit_error", "Too many pending requests, please retry later")
 		return
 	}
-	// Ensure wait count is decremented when function exits
-	defer h.concurrencyHelper.DecrementWaitCount(c.Request.Context(), subject.UserID)
+	if err == nil && canWait {
+		waitCounted = true
+	}
+	defer func() {
+		if waitCounted {
+			h.concurrencyHelper.DecrementWaitCount(c.Request.Context(), subject.UserID)
+		}
+	}()
 
 	// 1. First acquire user concurrency slot
 	userReleaseFunc, err := h.concurrencyHelper.AcquireUserSlotWithWait(c, subject.UserID, subject.Concurrency, reqStream, &streamStarted)
@@ -130,6 +141,11 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 		h.handleConcurrencyError(c, err, "user", streamStarted)
 		return
 	}
+	// User slot acquired: no longer waiting.
+	if waitCounted {
+		h.concurrencyHelper.DecrementWaitCount(c.Request.Context(), subject.UserID)
+		waitCounted = false
+	}
 	// 确保请求取消时也会释放槽位，避免长连接被动中断造成泄漏
 	userReleaseFunc = wrapReleaseOnDone(c.Request.Context(), userReleaseFunc)
 	if userReleaseFunc != nil {
@@ -167,15 +183,16 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 		}
 		account := selection.Account
 		log.Printf("[OpenAI Handler] Selected account: id=%d name=%s", account.ID, account.Name)
+		setOpsSelectedAccount(c, account.ID)
 
 		// 3. Acquire account concurrency slot
 		accountReleaseFunc := selection.ReleaseFunc
-		var accountWaitRelease func()
 		if !selection.Acquired {
 			if selection.WaitPlan == nil {
 				h.handleStreamingAwareError(c, http.StatusServiceUnavailable, "api_error", "No available accounts", streamStarted)
 				return
 			}
+			accountWaitCounted := false
 			canWait, err := h.concurrencyHelper.IncrementAccountWaitCount(c.Request.Context(), account.ID, selection.WaitPlan.MaxWaiting)
 			if err != nil {
 				log.Printf("Increment account wait count failed: %v", err)
@@ -183,12 +200,15 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 				log.Printf("Account wait queue full: account=%d", account.ID)
 				h.handleStreamingAwareError(c, http.StatusTooManyRequests, "rate_limit_error", "Too many pending requests, please retry later", streamStarted)
 				return
-			} else {
-				// Only set release function if increment succeeded
-				accountWaitRelease = func() {
+			}
+			if err == nil && canWait {
+				accountWaitCounted = true
+			}
+			defer func() {
+				if accountWaitCounted {
 					h.concurrencyHelper.DecrementAccountWaitCount(c.Request.Context(), account.ID)
 				}
-			}
+			}()
 
 			accountReleaseFunc, err = h.concurrencyHelper.AcquireAccountSlotWithWaitTimeout(
 				c,
@@ -199,29 +219,26 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 				&streamStarted,
 			)
 			if err != nil {
-				if accountWaitRelease != nil {
-					accountWaitRelease()
-				}
 				log.Printf("Account concurrency acquire failed: %v", err)
 				h.handleConcurrencyError(c, err, "account", streamStarted)
 				return
 			}
+			if accountWaitCounted {
+				h.concurrencyHelper.DecrementAccountWaitCount(c.Request.Context(), account.ID)
+				accountWaitCounted = false
+			}
 			if err := h.gatewayService.BindStickySession(c.Request.Context(), sessionHash, account.ID); err != nil {
 				log.Printf("Bind sticky session failed: %v", err)
 			}
 		}
 		// 账号槽位/等待计数需要在超时或断开时安全回收
 		accountReleaseFunc = wrapReleaseOnDone(c.Request.Context(), accountReleaseFunc)
-		accountWaitRelease = wrapReleaseOnDone(c.Request.Context(), accountWaitRelease)
 
 		// Forward request
 		result, err := h.gatewayService.Forward(c.Request.Context(), c, account, body)
 		if accountReleaseFunc != nil {
 			accountReleaseFunc()
 		}
-		if accountWaitRelease != nil {
-			accountWaitRelease()
-		}
 		if err != nil {
 			var failoverErr *service.UpstreamFailoverError
 			if errors.As(err, &failoverErr) {