fix(openai): preserve exponential capacity backoff

backend/internal/handler/failover_loop.go

@@ -36,6 +36,9 @@ const (
 	maxSameAccountRetries = 3
 	// sameAccountRetryDelay 同账号重试间隔
 	sameAccountRetryDelay = 500 * time.Millisecond
+	// maxRequestScopedRetryDelay 限制请求级瞬时错误的指数退避上限，避免高重试配置
+	// 将单次请求拖入分钟级等待。
+	maxRequestScopedRetryDelay = 8 * time.Second
 	// singleAccountBackoffDelay 单账号分组 503 退避重试固定延时。
 	// Service 层在 SingleAccountRetry 模式下已做充分原地重试（最多 3 次、总等待 30s），
 	// Handler 层只需短暂间隔后重新进入 Service 层即可。
@@ -52,6 +55,21 @@ const (
 // 语义上等同于「无可用账号」：候选账号都不满足分组的利润约束。
 const profitVetoExhaustedMessage = "No available accounts: all candidates rejected by group profit control"
 
+func sameAccountRetryDelayFor(failoverErr *service.UpstreamFailoverError, retryCount int) time.Duration {
+	if failoverErr == nil || !failoverErr.RequestScopedTransient || retryCount <= 1 {
+		return sameAccountRetryDelay
+	}
+
+	delay := sameAccountRetryDelay
+	for i := 1; i < retryCount; i++ {
+		if delay >= maxRequestScopedRetryDelay/2 {
+			return maxRequestScopedRetryDelay
+		}
+		delay *= 2
+	}
+	return delay
+}
+
 // FailoverState 跨循环迭代共享的 failover 状态
 type FailoverState struct {
 	SwitchCount           int
@@ -149,13 +167,15 @@ func (s *FailoverState) HandleFailoverError(
 	// 重试次数上限 retryLimit 由调用方传入（账号级 pool_mode_retry_count 配置）。
 	if failoverErr.RetryableOnSameAccount && s.SameAccountRetryCount[accountID] < retryLimit {
 		s.SameAccountRetryCount[accountID]++
+		retryDelay := sameAccountRetryDelayFor(failoverErr, s.SameAccountRetryCount[accountID])
 		logger.FromContext(ctx).Warn("gateway.failover_same_account_retry",
 			zap.Int64("account_id", accountID),
 			zap.Int("upstream_status", failoverErr.StatusCode),
 			zap.Int("same_account_retry_count", s.SameAccountRetryCount[accountID]),
 			zap.Int("same_account_retry_max", retryLimit),
+			zap.Duration("retry_delay", retryDelay),
 		)
-		if !sleepWithContext(ctx, sameAccountRetryDelay) {
+		if !sleepWithContext(ctx, retryDelay) {
 			return FailoverCanceled
 		}
 		return FailoverContinue

backend/internal/handler/failover_loop_test.go

@@ -31,6 +31,35 @@ func (m *mockTempUnscheduler) TempUnscheduleRetryableError(_ context.Context, ac
 	m.calls = append(m.calls, tempUnscheduleCall{accountID: accountID, failoverErr: failoverErr})
 }
 
+func TestSameAccountRetryDelayFor(t *testing.T) {
+	capacityErr := &service.UpstreamFailoverError{RequestScopedTransient: true}
+
+	for _, tc := range []struct {
+		name       string
+		retryCount int
+		want       time.Duration
+	}{
+		{name: "first retry", retryCount: 1, want: 500 * time.Millisecond},
+		{name: "second retry", retryCount: 2, want: time.Second},
+		{name: "third retry", retryCount: 3, want: 2 * time.Second},
+		{name: "fourth retry", retryCount: 4, want: 4 * time.Second},
+		{name: "fifth retry", retryCount: 5, want: 8 * time.Second},
+		{name: "capped retry", retryCount: 10, want: 8 * time.Second},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			require.Equal(t, tc.want, sameAccountRetryDelayFor(capacityErr, tc.retryCount))
+		})
+	}
+
+	t.Run("non request scoped errors keep fixed delay", func(t *testing.T) {
+		require.Equal(t, 500*time.Millisecond, sameAccountRetryDelayFor(&service.UpstreamFailoverError{}, 10))
+	})
+
+	t.Run("nil error keeps fixed delay", func(t *testing.T) {
+		require.Equal(t, 500*time.Millisecond, sameAccountRetryDelayFor(nil, 10))
+	})
+}
+
 // ---------------------------------------------------------------------------
 // Helper
 // ---------------------------------------------------------------------------

backend/internal/handler/openai_chat_completions.go

@@ -288,16 +288,18 @@ func (h *OpenAIGatewayHandler) ChatCompletions(c *gin.Context) {
 						retryLimit := account.GetPoolModeRetryCount()
 						if sameAccountRetryCount[account.ID] < retryLimit {
 							sameAccountRetryCount[account.ID]++
+							retryDelay := sameAccountRetryDelayFor(failoverErr, sameAccountRetryCount[account.ID])
 							reqLog.Warn("openai_chat_completions.pool_mode_same_account_retry",
 								zap.Int64("account_id", account.ID),
 								zap.Int("upstream_status", failoverErr.StatusCode),
 								zap.Int("retry_limit", retryLimit),
 								zap.Int("retry_count", sameAccountRetryCount[account.ID]),
+								zap.Duration("retry_delay", retryDelay),
 							)
 							select {
 							case <-c.Request.Context().Done():
 								return
-							case <-time.After(sameAccountRetryDelay):
+							case <-time.After(retryDelay):
 							}
 							continue
 						}

backend/internal/handler/openai_gateway_handler.go

@@ -610,16 +610,18 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 						retryLimit := account.GetPoolModeRetryCount()
 						if sameAccountRetryCount[account.ID] < retryLimit {
 							sameAccountRetryCount[account.ID]++
+							retryDelay := sameAccountRetryDelayFor(failoverErr, sameAccountRetryCount[account.ID])
 							reqLog.Warn("openai.pool_mode_same_account_retry",
 								zap.Int64("account_id", account.ID),
 								zap.Int("upstream_status", failoverErr.StatusCode),
 								zap.Int("retry_limit", retryLimit),
 								zap.Int("retry_count", sameAccountRetryCount[account.ID]),
+								zap.Duration("retry_delay", retryDelay),
 							)
 							select {
 							case <-c.Request.Context().Done():
 								return
-							case <-time.After(sameAccountRetryDelay):
+							case <-time.After(retryDelay):
 							}
 							continue
 						}
@@ -1158,16 +1160,18 @@ func (h *OpenAIGatewayHandler) Messages(c *gin.Context) {
 						retryLimit := account.GetPoolModeRetryCount()
 						if sameAccountRetryCount[account.ID] < retryLimit {
 							sameAccountRetryCount[account.ID]++
+							retryDelay := sameAccountRetryDelayFor(failoverErr, sameAccountRetryCount[account.ID])
 							reqLog.Warn("openai_messages.pool_mode_same_account_retry",
 								zap.Int64("account_id", account.ID),
 								zap.Int("upstream_status", failoverErr.StatusCode),
 								zap.Int("retry_limit", retryLimit),
 								zap.Int("retry_count", sameAccountRetryCount[account.ID]),
+								zap.Duration("retry_delay", retryDelay),
 							)
 							select {
 							case <-c.Request.Context().Done():
 								return
-							case <-time.After(sameAccountRetryDelay):
+							case <-time.After(retryDelay):
 							}
 							continue
 						}