feat: add TTFB timeout detection and improve stream handling

- Add stream first byte timeout (TTFB) detection to trigger failover
  when provider responds too slowly (configurable via STREAM_FIRST_BYTE_TIMEOUT)
- Add rate limit fail-open/fail-close strategy configuration
- Improve exception handling in stream prefetch with proper error classification
- Refactor UsageService with shared _prepare_usage_record method
- Add batch deletion for old usage records to avoid long transaction locks
- Update CLI adapters to use proper User-Agent headers for each CLI client
- Add composite indexes migration for usage table query optimization
- Fix streaming status display in frontend to show TTFB during streaming
- Remove sensitive JWT secret logging in auth service

alembic/versions/20251220_1500_add_usage_composite_indexes.py

@@ -0,0 +1,65 @@
+"""add usage table composite indexes for query optimization
+
+Revision ID: b2c3d4e5f6g7
+Revises: a1b2c3d4e5f6
+Create Date: 2025-12-20 15:00:00.000000+00:00
+
+"""
+from alembic import op
+from sqlalchemy import inspect
+
+# revision identifiers, used by Alembic.
+revision = 'b2c3d4e5f6g7'
+down_revision = 'a1b2c3d4e5f6'
+branch_labels = None
+depends_on = None
+
+
+def index_exists(table_name: str, index_name: str) -> bool:
+    """检查索引是否存在"""
+    bind = op.get_bind()
+    inspector = inspect(bind)
+    indexes = [idx['name'] for idx in inspector.get_indexes(table_name)]
+    return index_name in indexes
+
+
+def upgrade() -> None:
+    """为 usage 表添加复合索引以优化常见查询"""
+    # 1. user_id + created_at 复合索引 (用户用量查询)
+    if not index_exists('usage', 'idx_usage_user_created'):
+        op.create_index(
+            'idx_usage_user_created',
+            'usage',
+            ['user_id', 'created_at'],
+            postgresql_concurrently=True
+        )
+
+    # 2. api_key_id + created_at 复合索引 (API Key 用量查询)
+    if not index_exists('usage', 'idx_usage_apikey_created'):
+        op.create_index(
+            'idx_usage_apikey_created',
+            'usage',
+            ['api_key_id', 'created_at'],
+            postgresql_concurrently=True
+        )
+
+    # 3. provider + model + created_at 复合索引 (模型统计查询)
+    if not index_exists('usage', 'idx_usage_provider_model_created'):
+        op.create_index(
+            'idx_usage_provider_model_created',
+            'usage',
+            ['provider', 'model', 'created_at'],
+            postgresql_concurrently=True
+        )
+
+
+def downgrade() -> None:
+    """删除复合索引"""
+    if index_exists('usage', 'idx_usage_provider_model_created'):
+        op.drop_index('idx_usage_provider_model_created', table_name='usage')
+
+    if index_exists('usage', 'idx_usage_apikey_created'):
+        op.drop_index('idx_usage_apikey_created', table_name='usage')
+
+    if index_exists('usage', 'idx_usage_user_created'):
+        op.drop_index('idx_usage_user_created', table_name='usage')

frontend/src/features/usage/components/UsageRecordsTable.vue

@@ -366,14 +366,34 @@
             </div>
           </TableCell>
           <TableCell class="text-right py-4 w-[70px]">
+            <!-- pending 状态：只显示增长的总时间 -->
             <div
-              v-if="record.status === 'pending' || record.status === 'streaming'"
+              v-if="record.status === 'pending'"
               class="flex flex-col items-end text-xs gap-0.5"
             >
+              <span class="text-muted-foreground">-</span>
               <span class="text-primary tabular-nums">
                 {{ getElapsedTime(record) }}
               </span>
             </div>
+            <!-- streaming 状态：首字固定 + 总时间增长 -->
+            <div
+              v-else-if="record.status === 'streaming'"
+              class="flex flex-col items-end text-xs gap-0.5"
+            >
+              <span
+                v-if="record.first_byte_time_ms != null"
+                class="tabular-nums"
+              >{{ (record.first_byte_time_ms / 1000).toFixed(2) }}s</span>
+              <span
+                v-else
+                class="text-muted-foreground"
+              >-</span>
+              <span class="text-primary tabular-nums">
+                {{ getElapsedTime(record) }}
+              </span>
+            </div>
+            <!-- 已完成状态：首字 + 总耗时 -->
             <div
               v-else-if="record.response_time_ms != null"
               class="flex flex-col items-end text-xs gap-0.5"

src/api/handlers/base/base_handler.py

@@ -376,6 +376,9 @@ class BaseMessageHandler:
 
         使用 asyncio 后台任务执行数据库更新，避免阻塞流式传输
 
+        注意：TTFB（首字节时间）由 StreamContext.record_first_byte_time() 记录，
+        并在最终 record_success 时传递到数据库，避免重复记录导致数据不一致。
+
         Args:
             request_id: 请求 ID，如果不传则使用 self.request_id
         """
@@ -407,6 +410,9 @@ class BaseMessageHandler:
 
         使用 asyncio 后台任务执行数据库更新，避免阻塞流式传输
 
+        注意：TTFB（首字节时间）由 StreamContext.record_first_byte_time() 记录，
+        并在最终 record_success 时传递到数据库，避免重复记录导致数据不一致。
+
         Args:
             ctx: 流式上下文，包含 provider_name 和 mapped_model
         """

src/api/handlers/base/cli_handler_base.py

@@ -57,8 +57,10 @@ from src.models.database import (
     ProviderEndpoint,
     User,
 )
+from src.config.settings import config
 from src.services.provider.transport import build_provider_url
 from src.utils.sse_parser import SSEEventParser
+from src.utils.timeout import read_first_chunk_with_ttfb_timeout
 
 
 class CliMessageHandlerBase(BaseMessageHandler):
@@ -672,6 +674,8 @@ class CliMessageHandlerBase(BaseMessageHandler):
 
         同时检测 HTML 响应（通常是 base_url 配置错误导致返回网页）。
 
+        首次读取时会应用 TTFB（首字节超时）检测，超时则触发故障转移。
+
         Args:
             byte_iterator: 字节流迭代器
             provider: Provider 对象
@@ -684,6 +688,7 @@ class CliMessageHandlerBase(BaseMessageHandler):
         Raises:
             EmbeddedErrorException: 如果检测到嵌套错误
             ProviderNotAvailableException: 如果检测到 HTML 响应（配置错误）
+            ProviderTimeoutException: 如果首字节超时（TTFB timeout）
         """
         prefetched_chunks: list = []
         max_prefetch_lines = 5  # 最多预读5行来检测错误
@@ -704,7 +709,19 @@ class CliMessageHandlerBase(BaseMessageHandler):
             else:
                 provider_parser = self.parser
 
-            async for chunk in byte_iterator:
+            # 使用共享的 TTFB 超时函数读取首字节
+            ttfb_timeout = config.stream_first_byte_timeout
+            first_chunk, aiter = await read_first_chunk_with_ttfb_timeout(
+                byte_iterator,
+                timeout=ttfb_timeout,
+                request_id=self.request_id,
+                provider_name=str(provider.name),
+            )
+            prefetched_chunks.append(first_chunk)
+            buffer += first_chunk
+
+            # 继续读取剩余的预读数据
+            async for chunk in aiter:
                 prefetched_chunks.append(chunk)
                 buffer += chunk
 
@@ -785,12 +802,21 @@ class CliMessageHandlerBase(BaseMessageHandler):
                 if should_stop or line_count >= max_prefetch_lines:
                     break
 
-        except EmbeddedErrorException:
-            # 重新抛出嵌套错误
+        except (EmbeddedErrorException, ProviderTimeoutException, ProviderNotAvailableException):
+            # 重新抛出可重试的 Provider 异常，触发故障转移
             raise
+        except (OSError, IOError) as e:
+            # 网络 I/O 异常：记录警告，可能需要重试
+            logger.warning(
+                f"  [{self.request_id}] 预读流时发生网络异常: {type(e).__name__}: {e}"
+            )
         except Exception as e:
-            # 其他异常（如网络错误）在预读阶段发生，记录日志但不中断
-            logger.debug(f"  [{self.request_id}] 预读流时发生异常: {e}")
+            # 未预期的严重异常：记录错误并重新抛出，避免掩盖问题
+            logger.error(
+                f"  [{self.request_id}] 预读流时发生严重异常: {type(e).__name__}: {e}",
+                exc_info=True
+            )
+            raise
 
         return prefetched_chunks
 

src/api/handlers/base/stream_processor.py

@@ -25,10 +25,12 @@ from src.api.handlers.base.content_extractors import (
 from src.api.handlers.base.parsers import get_parser_for_format
 from src.api.handlers.base.response_parser import ResponseParser
 from src.api.handlers.base.stream_context import StreamContext
-from src.core.exceptions import EmbeddedErrorException
+from src.config.settings import config
+from src.core.exceptions import EmbeddedErrorException, ProviderTimeoutException
 from src.core.logger import logger
 from src.models.database import Provider, ProviderEndpoint
 from src.utils.sse_parser import SSEEventParser
+from src.utils.timeout import read_first_chunk_with_ttfb_timeout
 
 
 @dataclass
@@ -170,6 +172,8 @@ class StreamProcessor:
         某些 Provider（如 Gemini）可能返回 HTTP 200，但在响应体中包含错误信息。
         这种情况需要在流开始输出之前检测，以便触发重试逻辑。
 
+        首次读取时会应用 TTFB（首字节超时）检测，超时则触发故障转移。
+
         Args:
             byte_iterator: 字节流迭代器
             provider: Provider 对象
@@ -182,6 +186,7 @@ class StreamProcessor:
 
         Raises:
             EmbeddedErrorException: 如果检测到嵌套错误
+            ProviderTimeoutException: 如果首字节超时（TTFB timeout）
         """
         prefetched_chunks: list = []
         parser = self.get_parser_for_provider(ctx)
@@ -192,7 +197,19 @@ class StreamProcessor:
         decoder = codecs.getincrementaldecoder("utf-8")(errors="replace")
 
         try:
-            async for chunk in byte_iterator:
+            # 使用共享的 TTFB 超时函数读取首字节
+            ttfb_timeout = config.stream_first_byte_timeout
+            first_chunk, aiter = await read_first_chunk_with_ttfb_timeout(
+                byte_iterator,
+                timeout=ttfb_timeout,
+                request_id=self.request_id,
+                provider_name=str(provider.name),
+            )
+            prefetched_chunks.append(first_chunk)
+            buffer += first_chunk
+
+            # 继续读取剩余的预读数据
+            async for chunk in aiter:
                 prefetched_chunks.append(chunk)
                 buffer += chunk
 
@@ -262,10 +279,21 @@ class StreamProcessor:
                 if should_stop or line_count >= max_prefetch_lines:
                     break
 
-        except EmbeddedErrorException:
+        except (EmbeddedErrorException, ProviderTimeoutException):
+            # 重新抛出可重试的 Provider 异常，触发故障转移
             raise
+        except (OSError, IOError) as e:
+            # 网络 I/O <20><><EFBFBD>常：记录警告，可能需要重试
+            logger.warning(
+                f"  [{self.request_id}] 预读流时发生网络异常: {type(e).__name__}: {e}"
+            )
         except Exception as e:
-            logger.debug(f"  [{self.request_id}] 预读流时发生异常: {e}")
+            # 未预期的严重异常：记录错误并重新抛出，避免掩盖问题
+            logger.error(
+                f"  [{self.request_id}] 预读流时发生严重异常: {type(e).__name__}: {e}",
+                exc_info=True
+            )
+            raise
 
         return prefetched_chunks
 

src/api/handlers/claude_cli/adapter.py

@@ -115,7 +115,7 @@ class ClaudeCliAdapter(CliAdapterBase):
     ) -> Tuple[list, Optional[str]]:
         """查询 Claude API 支持的模型列表（带 CLI User-Agent）"""
         # 复用 ClaudeChatAdapter 的实现，添加 CLI User-Agent
-        cli_headers = {"User-Agent": config.internal_user_agent_claude}
+        cli_headers = {"User-Agent": config.internal_user_agent_claude_cli}
         if extra_headers:
             cli_headers.update(extra_headers)
         models, error = await ClaudeChatAdapter.fetch_models(

src/api/handlers/gemini_cli/adapter.py

@@ -112,7 +112,7 @@ class GeminiCliAdapter(CliAdapterBase):
     ) -> Tuple[list, Optional[str]]:
         """查询 Gemini API 支持的模型列表（带 CLI User-Agent）"""
         # 复用 GeminiChatAdapter 的实现，添加 CLI User-Agent
-        cli_headers = {"User-Agent": config.internal_user_agent_gemini}
+        cli_headers = {"User-Agent": config.internal_user_agent_gemini_cli}
         if extra_headers:
             cli_headers.update(extra_headers)
         models, error = await GeminiChatAdapter.fetch_models(

src/api/handlers/openai_cli/adapter.py

@@ -57,7 +57,7 @@ class OpenAICliAdapter(CliAdapterBase):
     ) -> Tuple[list, Optional[str]]:
         """查询 OpenAI 兼容 API 支持的模型列表（带 CLI User-Agent）"""
         # 复用 OpenAIChatAdapter 的实现，添加 CLI User-Agent
-        cli_headers = {"User-Agent": config.internal_user_agent_openai}
+        cli_headers = {"User-Agent": config.internal_user_agent_openai_cli}
         if extra_headers:
             cli_headers.update(extra_headers)
         models, error = await OpenAIChatAdapter.fetch_models(

src/config/settings.py

@@ -56,10 +56,11 @@ class Config:
 
         # Redis 依赖策略（生产默认必需，开发默认可选，可通过 REDIS_REQUIRED 覆盖）
         redis_required_env = os.getenv("REDIS_REQUIRED")
-        if redis_required_env is None:
-            self.require_redis = self.environment not in {"development", "test", "testing"}
-        else:
+        if redis_required_env is not None:
             self.require_redis = redis_required_env.lower() == "true"
+        else:
+            # 保持向后兼容：开发环境可选，生产环境必需
+            self.require_redis = self.environment not in {"development", "test", "testing"}
 
         # CORS配置 - 使用环境变量配置允许的源
         # 格式: 逗号分隔的域名列表,如 "http://localhost:3000,https://example.com"
@@ -133,6 +134,18 @@ class Config:
         self.concurrency_slot_ttl = int(os.getenv("CONCURRENCY_SLOT_TTL", "600"))
         self.cache_reservation_ratio = float(os.getenv("CACHE_RESERVATION_RATIO", "0.1"))
 
+        # 限流降级策略配置
+        # RATE_LIMIT_FAIL_OPEN: 当限流服务（Redis）异常时的行为
+        #
+        # True (默认): fail-open - 放行请求（优先可用性）
+        #   风险：Redis 故障期间无法限流，可能被滥用
+        #   适用：API 网关作为关键基础设施，必须保持高可用
+        #
+        # False: fail-close - 拒绝所有请求（优先安全性）
+        #   风险：Redis 故障会导致 API 网关不可用
+        #   适用：有严格速率限制要求的安全敏感场景
+        self.rate_limit_fail_open = os.getenv("RATE_LIMIT_FAIL_OPEN", "true").lower() == "true"
+
         # HTTP 请求超时配置（秒）
         self.http_connect_timeout = float(os.getenv("HTTP_CONNECT_TIMEOUT", "10.0"))
         self.http_write_timeout = float(os.getenv("HTTP_WRITE_TIMEOUT", "60.0"))
@@ -141,19 +154,22 @@ class Config:
         # 流式处理配置
         # STREAM_PREFETCH_LINES: 预读行数，用于检测嵌套错误
         # STREAM_STATS_DELAY: 统计记录延迟（秒），等待流完全关闭
+        # STREAM_FIRST_BYTE_TIMEOUT: 首字节超时（秒），等待首字节超过此时间触发故障转移
+        #   范围: 10-120 秒，默认 30 秒（必须小于 http_write_timeout 避免竞态）
         self.stream_prefetch_lines = int(os.getenv("STREAM_PREFETCH_LINES", "5"))
         self.stream_stats_delay = float(os.getenv("STREAM_STATS_DELAY", "0.1"))
+        self.stream_first_byte_timeout = self._parse_ttfb_timeout()
 
         # 内部请求 User-Agent 配置（用于查询上游模型列表等）
-        # 可通过环境变量覆盖默认值
-        self.internal_user_agent_claude = os.getenv(
-            "CLAUDE_USER_AGENT", "claude-cli/1.0"
+        # 可通过环境变量覆盖默认值，模拟对应 CLI 客户端
+        self.internal_user_agent_claude_cli = os.getenv(
+            "CLAUDE_CLI_USER_AGENT", "claude-code/1.0.1"
         )
-        self.internal_user_agent_openai = os.getenv(
-            "OPENAI_USER_AGENT", "openai-cli/1.0"
+        self.internal_user_agent_openai_cli = os.getenv(
+            "OPENAI_CLI_USER_AGENT", "openai-codex/1.0"
         )
-        self.internal_user_agent_gemini = os.getenv(
-            "GEMINI_USER_AGENT", "gemini-cli/1.0"
+        self.internal_user_agent_gemini_cli = os.getenv(
+            "GEMINI_CLI_USER_AGENT", "gemini-cli/0.1.0"
         )
 
         # 验证连接池配置
@@ -177,6 +193,39 @@ class Config:
         """智能计算最大溢出连接数 - 与 pool_size 相同"""
         return self.db_pool_size
 
+    def _parse_ttfb_timeout(self) -> float:
+        """
+        解析 TTFB 超时配置，带错误处理和范围限制
+
+        TTFB (Time To First Byte) 用于检测慢响应的 Provider，超时触发故障转移。
+        此值必须小于 http_write_timeout，避免竞态条件。
+
+        Returns:
+            超时时间（秒），范围 10-120，默认 30
+        """
+        default_timeout = 30.0
+        min_timeout = 10.0
+        max_timeout = 120.0  # 必须小于 http_write_timeout (默认 60s) 的 2 倍
+
+        raw_value = os.getenv("STREAM_FIRST_BYTE_TIMEOUT", str(default_timeout))
+        try:
+            timeout = float(raw_value)
+        except ValueError:
+            # 延迟导入，避免循环依赖（Config 初始化时 logger 可能未就绪）
+            self._ttfb_config_warning = (
+                f"无效的 STREAM_FIRST_BYTE_TIMEOUT 配置 '{raw_value}'，使用默认值 {default_timeout}秒"
+            )
+            return default_timeout
+
+        # 范围限制
+        clamped = max(min_timeout, min(max_timeout, timeout))
+        if clamped != timeout:
+            self._ttfb_config_warning = (
+                f"STREAM_FIRST_BYTE_TIMEOUT={timeout}秒超出范围 [{min_timeout}-{max_timeout}]，"
+                f"已调整为 {clamped}秒"
+            )
+        return clamped
+
     def _validate_pool_config(self) -> None:
         """验证连接池配置是否安全"""
         total_per_worker = self.db_pool_size + self.db_max_overflow
@@ -224,6 +273,10 @@ class Config:
         if hasattr(self, "_pool_config_warning") and self._pool_config_warning:
             logger.warning(self._pool_config_warning)
 
+        # TTFB 超时配置警告
+        if hasattr(self, "_ttfb_config_warning") and self._ttfb_config_warning:
+            logger.warning(self._ttfb_config_warning)
+
         # 管理员密码检查（必须在环境变量中设置）
         if hasattr(self, "_missing_admin_password") and self._missing_admin_password:
             logger.error("必须设置 ADMIN_PASSWORD 环境变量！")

src/middleware/plugin_middleware.py

@@ -336,10 +336,44 @@ class PluginMiddleware:
                     )
                 return result
             return None
-        except Exception as e:
-            logger.error(f"Rate limit error: {e}")
-            # 发生错误时允许请求通过
+        except ConnectionError as e:
+            # Redis 连接错误：根据配置决定
+            logger.warning(f"Rate limit connection error: {e}")
+            if config.rate_limit_fail_open:
                 return None
+            else:
+                return RateLimitResult(
+                    allowed=False,
+                    remaining=0,
+                    retry_after=30,
+                    message="Rate limit service unavailable"
+                )
+        except TimeoutError as e:
+            # 超时错误：可能是负载过高，根据配置决定
+            logger.warning(f"Rate limit timeout: {e}")
+            if config.rate_limit_fail_open:
+                return None
+            else:
+                return RateLimitResult(
+                    allowed=False,
+                    remaining=0,
+                    retry_after=30,
+                    message="Rate limit service timeout"
+                )
+        except Exception as e:
+            logger.error(f"Rate limit error: {type(e).__name__}: {e}")
+            # 其他异常：根据配置决定
+            if config.rate_limit_fail_open:
+                # fail-open: 异常时放行请求（优先可用性）
+                return None
+            else:
+                # fail-close: 异常时拒绝请求（优先安全性）
+                return RateLimitResult(
+                    allowed=False,
+                    remaining=0,
+                    retry_after=60,
+                    message="Rate limit service error"
+                )
 
     async def _call_pre_request_plugins(self, request: Request) -> None:
         """调用请求前的插件（当前保留扩展点）"""

src/services/auth/service.py

@@ -27,7 +27,7 @@ if not config.jwt_secret_key:
     if config.environment == "production":
         raise ValueError("JWT_SECRET_KEY must be set in production environment!")
     config.jwt_secret_key = secrets.token_urlsafe(32)
-    logger.warning(f"JWT_SECRET_KEY未在环境变量中找到，已生成随机密钥用于开发: {config.jwt_secret_key[:10]}...")
+    logger.warning("JWT_SECRET_KEY未在环境变量中找到，已生成随机密钥用于开发")
     logger.warning("生产环境请设置JWT_SECRET_KEY环境变量!")
 
 JWT_SECRET_KEY = config.jwt_secret_key

src/services/usage/service.py

@@ -3,6 +3,7 @@
 """
 
 import uuid
+from dataclasses import dataclass
 from datetime import datetime, timedelta, timezone
 from typing import Any, Dict, List, Optional, Tuple
 
@@ -16,6 +17,71 @@ from src.services.model.cost import ModelCostService
 from src.services.system.config import SystemConfigService
 
 
+@dataclass
+class UsageRecordParams:
+    """用量记录参数数据类，用于在内部方法间传递数据"""
+    db: Session
+    user: Optional[User]
+    api_key: Optional[ApiKey]
+    provider: str
+    model: str
+    input_tokens: int
+    output_tokens: int
+    cache_creation_input_tokens: int
+    cache_read_input_tokens: int
+    request_type: str
+    api_format: Optional[str]
+    is_stream: bool
+    response_time_ms: Optional[int]
+    first_byte_time_ms: Optional[int]
+    status_code: int
+    error_message: Optional[str]
+    metadata: Optional[Dict[str, Any]]
+    request_headers: Optional[Dict[str, Any]]
+    request_body: Optional[Any]
+    provider_request_headers: Optional[Dict[str, Any]]
+    response_headers: Optional[Dict[str, Any]]
+    response_body: Optional[Any]
+    request_id: str
+    provider_id: Optional[str]
+    provider_endpoint_id: Optional[str]
+    provider_api_key_id: Optional[str]
+    status: str
+    cache_ttl_minutes: Optional[int]
+    use_tiered_pricing: bool
+    target_model: Optional[str]
+
+    def __post_init__(self) -> None:
+        """验证关键字段，确保数据完整性"""
+        # Token 数量不能为负数
+        if self.input_tokens < 0:
+            raise ValueError(f"input_tokens 不能为负数: {self.input_tokens}")
+        if self.output_tokens < 0:
+            raise ValueError(f"output_tokens 不能为负数: {self.output_tokens}")
+        if self.cache_creation_input_tokens < 0:
+            raise ValueError(
+                f"cache_creation_input_tokens 不能为负数: {self.cache_creation_input_tokens}"
+            )
+        if self.cache_read_input_tokens < 0:
+            raise ValueError(
+                f"cache_read_input_tokens 不能为负数: {self.cache_read_input_tokens}"
+            )
+
+        # 响应时间不能为负数
+        if self.response_time_ms is not None and self.response_time_ms < 0:
+            raise ValueError(f"response_time_ms 不能为负数: {self.response_time_ms}")
+        if self.first_byte_time_ms is not None and self.first_byte_time_ms < 0:
+            raise ValueError(f"first_byte_time_ms 不能为负数: {self.first_byte_time_ms}")
+
+        # HTTP 状态码范围校验
+        if not (100 <= self.status_code <= 599):
+            raise ValueError(f"无效的 HTTP 状态码: {self.status_code}")
+
+        # 状态值校验
+        valid_statuses = {"pending", "streaming", "completed", "failed"}
+        if self.status not in valid_statuses:
+            raise ValueError(f"无效的状态值: {self.status}，有效值: {valid_statuses}")
+
 
 class UsageService:
     """用量统计服务"""
@@ -471,6 +537,97 @@ class UsageService:
             cache_ttl_minutes=cache_ttl_minutes,
         )
 
+    @classmethod
+    async def _prepare_usage_record(
+        cls,
+        params: UsageRecordParams,
+    ) -> Tuple[Dict[str, Any], float]:
+        """准备用量记录的共享逻辑
+
+        此方法提取了 record_usage 和 record_usage_async 的公共处理逻辑：
+        - 获取费率倍数
+        - 计算成本
+        - 构建 Usage 参数
+
+        Args:
+            params: 用量记录参数数据类
+
+        Returns:
+            (usage_params 字典, total_cost 总成本)
+        """
+        # 获取费率倍数和是否免费套餐
+        actual_rate_multiplier, is_free_tier = await cls._get_rate_multiplier_and_free_tier(
+            params.db, params.provider_api_key_id, params.provider_id
+        )
+
+        # 计算成本
+        is_failed_request = params.status_code >= 400 or params.error_message is not None
+        (
+            input_price, output_price, cache_creation_price, cache_read_price, request_price,
+            input_cost, output_cost, cache_creation_cost, cache_read_cost, cache_cost,
+            request_cost, total_cost, _tier_index
+        ) = await cls._calculate_costs(
+            db=params.db,
+            provider=params.provider,
+            model=params.model,
+            input_tokens=params.input_tokens,
+            output_tokens=params.output_tokens,
+            cache_creation_input_tokens=params.cache_creation_input_tokens,
+            cache_read_input_tokens=params.cache_read_input_tokens,
+            api_format=params.api_format,
+            cache_ttl_minutes=params.cache_ttl_minutes,
+            use_tiered_pricing=params.use_tiered_pricing,
+            is_failed_request=is_failed_request,
+        )
+
+        # 构建 Usage 参数
+        usage_params = cls._build_usage_params(
+            db=params.db,
+            user=params.user,
+            api_key=params.api_key,
+            provider=params.provider,
+            model=params.model,
+            input_tokens=params.input_tokens,
+            output_tokens=params.output_tokens,
+            cache_creation_input_tokens=params.cache_creation_input_tokens,
+            cache_read_input_tokens=params.cache_read_input_tokens,
+            request_type=params.request_type,
+            api_format=params.api_format,
+            is_stream=params.is_stream,
+            response_time_ms=params.response_time_ms,
+            first_byte_time_ms=params.first_byte_time_ms,
+            status_code=params.status_code,
+            error_message=params.error_message,
+            metadata=params.metadata,
+            request_headers=params.request_headers,
+            request_body=params.request_body,
+            provider_request_headers=params.provider_request_headers,
+            response_headers=params.response_headers,
+            response_body=params.response_body,
+            request_id=params.request_id,
+            provider_id=params.provider_id,
+            provider_endpoint_id=params.provider_endpoint_id,
+            provider_api_key_id=params.provider_api_key_id,
+            status=params.status,
+            target_model=params.target_model,
+            input_cost=input_cost,
+            output_cost=output_cost,
+            cache_creation_cost=cache_creation_cost,
+            cache_read_cost=cache_read_cost,
+            cache_cost=cache_cost,
+            request_cost=request_cost,
+            total_cost=total_cost,
+            input_price=input_price,
+            output_price=output_price,
+            cache_creation_price=cache_creation_price,
+            cache_read_price=cache_read_price,
+            request_price=request_price,
+            actual_rate_multiplier=actual_rate_multiplier,
+            is_free_tier=is_free_tier,
+        )
+
+        return usage_params, total_cost
+
     @classmethod
     async def record_usage_async(
         cls,
@@ -516,76 +673,25 @@ class UsageService:
         if request_id is None:
             request_id = str(uuid.uuid4())[:8]
 
-        # 获取费率倍数和是否免费套餐
-        actual_rate_multiplier, is_free_tier = await cls._get_rate_multiplier_and_free_tier(
-            db, provider_api_key_id, provider_id
-        )
-
-        # 计算成本
-        is_failed_request = status_code >= 400 or error_message is not None
-        (
-            input_price, output_price, cache_creation_price, cache_read_price, request_price,
-            input_cost, output_cost, cache_creation_cost, cache_read_cost, cache_cost,
-            request_cost, total_cost, tier_index
-        ) = await cls._calculate_costs(
-            db=db,
-            provider=provider,
-            model=model,
-            input_tokens=input_tokens,
-            output_tokens=output_tokens,
+        # 使用共享逻辑准备记录参数
+        params = UsageRecordParams(
+            db=db, user=user, api_key=api_key, provider=provider, model=model,
+            input_tokens=input_tokens, output_tokens=output_tokens,
             cache_creation_input_tokens=cache_creation_input_tokens,
             cache_read_input_tokens=cache_read_input_tokens,
-            api_format=api_format,
-            cache_ttl_minutes=cache_ttl_minutes,
-            use_tiered_pricing=use_tiered_pricing,
-            is_failed_request=is_failed_request,
-        )
-
-        # 构建 Usage 参数
-        usage_params = cls._build_usage_params(
-            db=db,
-            user=user,
-            api_key=api_key,
-            provider=provider,
-            model=model,
-            input_tokens=input_tokens,
-            output_tokens=output_tokens,
-            cache_creation_input_tokens=cache_creation_input_tokens,
-            cache_read_input_tokens=cache_read_input_tokens,
-            request_type=request_type,
-            api_format=api_format,
-            is_stream=is_stream,
-            response_time_ms=response_time_ms,
-            first_byte_time_ms=first_byte_time_ms,
-            status_code=status_code,
-            error_message=error_message,
-            metadata=metadata,
-            request_headers=request_headers,
-            request_body=request_body,
+            request_type=request_type, api_format=api_format, is_stream=is_stream,
+            response_time_ms=response_time_ms, first_byte_time_ms=first_byte_time_ms,
+            status_code=status_code, error_message=error_message, metadata=metadata,
+            request_headers=request_headers, request_body=request_body,
             provider_request_headers=provider_request_headers,
-            response_headers=response_headers,
-            response_body=response_body,
-            request_id=request_id,
-            provider_id=provider_id,
+            response_headers=response_headers, response_body=response_body,
+            request_id=request_id, provider_id=provider_id,
             provider_endpoint_id=provider_endpoint_id,
-            provider_api_key_id=provider_api_key_id,
-            status=status,
+            provider_api_key_id=provider_api_key_id, status=status,
+            cache_ttl_minutes=cache_ttl_minutes, use_tiered_pricing=use_tiered_pricing,
             target_model=target_model,
-            input_cost=input_cost,
-            output_cost=output_cost,
-            cache_creation_cost=cache_creation_cost,
-            cache_read_cost=cache_read_cost,
-            cache_cost=cache_cost,
-            request_cost=request_cost,
-            total_cost=total_cost,
-            input_price=input_price,
-            output_price=output_price,
-            cache_creation_price=cache_creation_price,
-            cache_read_price=cache_read_price,
-            request_price=request_price,
-            actual_rate_multiplier=actual_rate_multiplier,
-            is_free_tier=is_free_tier,
         )
+        usage_params, _ = await cls._prepare_usage_record(params)
 
         # 创建 Usage 记录
         usage = Usage(**usage_params)
@@ -660,76 +766,25 @@ class UsageService:
         if request_id is None:
             request_id = str(uuid.uuid4())[:8]
 
-        # 获取费率倍数和是否免费套餐
-        actual_rate_multiplier, is_free_tier = await cls._get_rate_multiplier_and_free_tier(
-            db, provider_api_key_id, provider_id
-        )
-
-        # 计算成本
-        is_failed_request = status_code >= 400 or error_message is not None
-        (
-            input_price, output_price, cache_creation_price, cache_read_price, request_price,
-            input_cost, output_cost, cache_creation_cost, cache_read_cost, cache_cost,
-            request_cost, total_cost, _tier_index
-        ) = await cls._calculate_costs(
-            db=db,
-            provider=provider,
-            model=model,
-            input_tokens=input_tokens,
-            output_tokens=output_tokens,
+        # 使用共享逻辑准备记录参数
+        params = UsageRecordParams(
+            db=db, user=user, api_key=api_key, provider=provider, model=model,
+            input_tokens=input_tokens, output_tokens=output_tokens,
             cache_creation_input_tokens=cache_creation_input_tokens,
             cache_read_input_tokens=cache_read_input_tokens,
-            api_format=api_format,
-            cache_ttl_minutes=cache_ttl_minutes,
-            use_tiered_pricing=use_tiered_pricing,
-            is_failed_request=is_failed_request,
-        )
-
-        # 构建 Usage 参数
-        usage_params = cls._build_usage_params(
-            db=db,
-            user=user,
-            api_key=api_key,
-            provider=provider,
-            model=model,
-            input_tokens=input_tokens,
-            output_tokens=output_tokens,
-            cache_creation_input_tokens=cache_creation_input_tokens,
-            cache_read_input_tokens=cache_read_input_tokens,
-            request_type=request_type,
-            api_format=api_format,
-            is_stream=is_stream,
-            response_time_ms=response_time_ms,
-            first_byte_time_ms=first_byte_time_ms,
-            status_code=status_code,
-            error_message=error_message,
-            metadata=metadata,
-            request_headers=request_headers,
-            request_body=request_body,
+            request_type=request_type, api_format=api_format, is_stream=is_stream,
+            response_time_ms=response_time_ms, first_byte_time_ms=first_byte_time_ms,
+            status_code=status_code, error_message=error_message, metadata=metadata,
+            request_headers=request_headers, request_body=request_body,
             provider_request_headers=provider_request_headers,
-            response_headers=response_headers,
-            response_body=response_body,
-            request_id=request_id,
-            provider_id=provider_id,
+            response_headers=response_headers, response_body=response_body,
+            request_id=request_id, provider_id=provider_id,
             provider_endpoint_id=provider_endpoint_id,
-            provider_api_key_id=provider_api_key_id,
-            status=status,
+            provider_api_key_id=provider_api_key_id, status=status,
+            cache_ttl_minutes=cache_ttl_minutes, use_tiered_pricing=use_tiered_pricing,
             target_model=target_model,
-            input_cost=input_cost,
-            output_cost=output_cost,
-            cache_creation_cost=cache_creation_cost,
-            cache_read_cost=cache_read_cost,
-            cache_cost=cache_cost,
-            request_cost=request_cost,
-            total_cost=total_cost,
-            input_price=input_price,
-            output_price=output_price,
-            cache_creation_price=cache_creation_price,
-            cache_read_price=cache_read_price,
-            request_price=request_price,
-            actual_rate_multiplier=actual_rate_multiplier,
-            is_free_tier=is_free_tier,
         )
+        usage_params, total_cost = await cls._prepare_usage_record(params)
 
         # 检查是否已存在相同 request_id 的记录
         existing_usage = db.query(Usage).filter(Usage.request_id == request_id).first()
@@ -751,7 +806,7 @@ class UsageService:
             api_key = db.merge(api_key)
 
         # 使用原子更新避免并发竞态条件
-        from sqlalchemy import func, update
+        from sqlalchemy import func as sql_func, update
         from src.models.database import ApiKey as ApiKeyModel, User as UserModel, GlobalModel
 
         # 更新用户使用量（独立 Key 不计入创建者的使用记录）
@@ -762,7 +817,7 @@ class UsageService:
                 .values(
                     used_usd=UserModel.used_usd + total_cost,
                     total_usd=UserModel.total_usd + total_cost,
-                    updated_at=func.now(),
+                    updated_at=sql_func.now(),
                 )
             )
 
@@ -776,8 +831,8 @@ class UsageService:
                         total_requests=ApiKeyModel.total_requests + 1,
                         total_cost_usd=ApiKeyModel.total_cost_usd + total_cost,
                         balance_used_usd=ApiKeyModel.balance_used_usd + total_cost,
-                        last_used_at=func.now(),
-                        updated_at=func.now(),
+                        last_used_at=sql_func.now(),
+                        updated_at=sql_func.now(),
                     )
                 )
             else:
@@ -787,8 +842,8 @@ class UsageService:
                     .values(
                         total_requests=ApiKeyModel.total_requests + 1,
                         total_cost_usd=ApiKeyModel.total_cost_usd + total_cost,
-                        last_used_at=func.now(),
-                        updated_at=func.now(),
+                        last_used_at=sql_func.now(),
+                        updated_at=sql_func.now(),
                     )
                 )
 
@@ -1121,19 +1176,48 @@ class UsageService:
         ]
 
     @staticmethod
-    def cleanup_old_usage_records(db: Session, days_to_keep: int = 90) -> int:
-        """清理旧的使用记录"""
+    def cleanup_old_usage_records(
+        db: Session, days_to_keep: int = 90, batch_size: int = 1000
+    ) -> int:
+        """清理旧的使用记录（分批删除避免长事务锁定）
 
+        Args:
+            db: 数据库会话
+            days_to_keep: 保留天数，默认 90 天
+            batch_size: 每批删除数量，默认 1000 条
+
+        Returns:
+            删除的总记录数
+        """
         cutoff_date = datetime.now(timezone.utc) - timedelta(days=days_to_keep)
+        total_deleted = 0
 
-        # 删除旧记录
-        deleted = db.query(Usage).filter(Usage.created_at < cutoff_date).delete()
+        while True:
+            # 查询待删除的 ID（使用新索引 idx_usage_user_created）
+            batch_ids = (
+                db.query(Usage.id)
+                .filter(Usage.created_at < cutoff_date)
+                .limit(batch_size)
+                .all()
+            )
 
+            if not batch_ids:
+                break
+
+            # 批量删除
+            deleted_count = (
+                db.query(Usage)
+                .filter(Usage.id.in_([row.id for row in batch_ids]))
+                .delete(synchronize_session=False)
+            )
             db.commit()
+            total_deleted += deleted_count
 
-        logger.info(f"清理使用记录: 删除 {deleted} 条超过 {days_to_keep} 天的记录")
+            logger.debug(f"清理使用记录: 本批删除 {deleted_count} 条")
 
-        return deleted
+        logger.info(f"清理使用记录: 共删除 {total_deleted} 条超过 {days_to_keep} 天的记录")
+
+        return total_deleted
 
     # ========== 请求状态追踪方法 ==========
 
@@ -1219,6 +1303,7 @@ class UsageService:
         error_message: Optional[str] = None,
         provider: Optional[str] = None,
         target_model: Optional[str] = None,
+        first_byte_time_ms: Optional[int] = None,
     ) -> Optional[Usage]:
         """
         快速更新使用记录状态
@@ -1230,6 +1315,7 @@ class UsageService:
             error_message: 错误消息（仅在 failed 状态时使用）
             provider: 提供商名称（可选，streaming 状态时更新）
             target_model: 映射后的目标模型名（可选）
+            first_byte_time_ms: 首字时间/TTFB（可选，streaming 状态时更新）
 
         Returns:
             更新后的 Usage 记录，如果未找到则返回 None
@@ -1247,6 +1333,8 @@ class UsageService:
             usage.provider = provider
         if target_model:
             usage.target_model = target_model
+        if first_byte_time_ms is not None:
+            usage.first_byte_time_ms = first_byte_time_ms
 
         db.commit()
 

src/services/usage/stream.py

@@ -5,6 +5,7 @@
 
 import json
 import re
+import time
 from typing import Any, AsyncIterator, Dict, Optional, Tuple
 
 from sqlalchemy.orm import Session
@@ -457,26 +458,32 @@ class StreamUsageTracker:
 
         logger.debug(f"ID:{self.request_id} | 开始跟踪流式响应 | 估算输入tokens:{self.input_tokens}")
 
-        # 更新状态为 streaming，同时更新 provider
-        if self.request_id:
-            try:
-                from src.services.usage.service import UsageService
-                UsageService.update_usage_status(
-                    db=self.db,
-                    request_id=self.request_id,
-                    status="streaming",
-                    provider=self.provider,
-                )
-            except Exception as e:
-                logger.warning(f"更新使用记录状态为 streaming 失败: {e}")
-
         chunk_count = 0
+        first_chunk_received = False
         try:
             async for chunk in stream:
                 chunk_count += 1
                 # 保存原始字节流（用于错误诊断）
                 self.raw_chunks.append(chunk)
 
+                # 第一个 chunk 收到时，更新状态为 streaming 并记录 TTFB
+                if not first_chunk_received:
+                    first_chunk_received = True
+                    if self.request_id:
+                        try:
+                            # 计算 TTFB（使用请求原始开始时间或 track_stream 开始时间）
+                            base_time = self.request_start_time or self.start_time
+                            first_byte_time_ms = int((time.time() - base_time) * 1000) if base_time else None
+                            UsageService.update_usage_status(
+                                db=self.db,
+                                request_id=self.request_id,
+                                status="streaming",
+                                provider=self.provider,
+                                first_byte_time_ms=first_byte_time_ms,
+                            )
+                        except Exception as e:
+                            logger.warning(f"更新使用记录状态为 streaming 失败: {e}")
+
                 # 返回原始块给客户端
                 yield chunk
 

src/utils/timeout.py

@@ -139,3 +139,83 @@ async def with_timeout_context(timeout: float, operation_name: str = "operation"
         # Python 3.10 及以下版本的兼容实现
         # 注意：这个简单实现不支持嵌套取消
         pass
+
+
+async def read_first_chunk_with_ttfb_timeout(
+    byte_iterator: Any,
+    timeout: float,
+    request_id: str,
+    provider_name: str,
+) -> tuple[bytes, Any]:
+    """
+    读取流的首字节并应用 TTFB 超时检测
+
+    首字节超时（Time To First Byte）用于检测慢响应的 Provider，
+    超时时触发故障转移到其他可用的 Provider。
+
+    Args:
+        byte_iterator: 异步字节流迭代器
+        timeout: TTFB 超时时间（秒）
+        request_id: 请求 ID（用于日志）
+        provider_name: Provider 名称（用于日志和异常）
+
+    Returns:
+        (first_chunk, aiter): 首个字节块和异步迭代器
+
+    Raises:
+        ProviderTimeoutException: 如果首字节超时
+    """
+    from src.core.exceptions import ProviderTimeoutException
+
+    aiter = byte_iterator.__aiter__()
+
+    try:
+        first_chunk = await asyncio.wait_for(aiter.__anext__(), timeout=timeout)
+        return first_chunk, aiter
+    except asyncio.TimeoutError:
+        # 完整的资源清理：先关闭迭代器，再关闭底层响应
+        await _cleanup_iterator_resources(aiter, request_id)
+        logger.warning(
+            f"  [{request_id}] 流首字节超时 (TTFB): "
+            f"Provider={provider_name}, timeout={timeout}s"
+        )
+        raise ProviderTimeoutException(
+            provider_name=provider_name,
+            timeout=int(timeout),
+        )
+
+
+async def _cleanup_iterator_resources(aiter: Any, request_id: str) -> None:
+    """
+    清理异步迭代器及其底层资源
+
+    确保在 TTFB 超时后正确释放 HTTP 连接，避免连接泄漏。
+
+    Args:
+        aiter: 异步迭代器
+        request_id: 请求 ID（用于日志）
+    """
+    # 1. 关闭迭代器本身
+    if hasattr(aiter, "aclose"):
+        try:
+            await aiter.aclose()
+        except Exception as e:
+            logger.debug(f"  [{request_id}] 关闭迭代器失败: {e}")
+
+    # 2. 关闭底层响应对象（httpx.Response）
+    # 迭代器可能持有 _response 属性指向底层响应
+    response = getattr(aiter, "_response", None)
+    if response is not None and hasattr(response, "aclose"):
+        try:
+            await response.aclose()
+        except Exception as e:
+            logger.debug(f"  [{request_id}] 关闭底层响应失败: {e}")
+
+    # 3. 尝试关闭 httpx 流（如果迭代器是 httpx 的 aiter_bytes）
+    # httpx 的 Response.aiter_bytes() 返回的生成器可能有 _stream 属性
+    stream = getattr(aiter, "_stream", None)
+    if stream is not None and hasattr(stream, "aclose"):
+        try:
+            await stream.aclose()
+        except Exception as e:
+            logger.debug(f"  [{request_id}] 关闭流对象失败: {e}")