429 lines
15 KiB
Python
429 lines
15 KiB
Python
"""
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Standardized FastAPI Service Base
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Provides a unified approach for creating FastAPI microservices with common patterns:
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- Logging setup
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- Metrics initialization
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- Health checks
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- Database initialization
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- CORS middleware
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- Exception handlers
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- Lifespan management
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"""
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import os
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import structlog
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from typing import Optional, List, Dict, Callable, Any, TYPE_CHECKING
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from contextlib import asynccontextmanager
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from fastapi import FastAPI, Request
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from fastapi.middleware.cors import CORSMiddleware
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from fastapi.responses import JSONResponse
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from fastapi.routing import APIRouter
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from shared.monitoring import setup_logging
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from shared.monitoring.metrics import setup_metrics_early
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from shared.monitoring.health_checks import setup_fastapi_health_checks
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from shared.database.base import DatabaseManager
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if TYPE_CHECKING:
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import uvicorn
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class BaseFastAPIService:
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"""
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Base class for FastAPI microservices with standardized patterns
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"""
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def __init__(
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self,
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service_name: str,
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app_name: str,
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description: str,
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version: str = "1.0.0",
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log_level: str = "INFO",
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cors_origins: Optional[List[str]] = None,
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api_prefix: str = "/api/v1",
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database_manager: Optional[DatabaseManager] = None,
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expected_tables: Optional[List[str]] = None,
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custom_health_checks: Optional[Dict[str, Callable[[], Any]]] = None,
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enable_metrics: bool = True,
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enable_health_checks: bool = True,
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enable_cors: bool = True,
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enable_exception_handlers: bool = True,
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enable_messaging: bool = False,
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custom_metrics: Optional[Dict[str, Dict[str, Any]]] = None,
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alert_service_class: Optional[type] = None
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):
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self.service_name = service_name
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self.app_name = app_name
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self.description = description
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self.version = version
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self.log_level = log_level
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self.cors_origins = cors_origins or ["*"]
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self.api_prefix = api_prefix
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self.database_manager = database_manager
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self.expected_tables = expected_tables
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self.custom_health_checks = custom_health_checks or {}
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self.enable_metrics = enable_metrics
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self.enable_health_checks = enable_health_checks
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self.enable_cors = enable_cors
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self.enable_exception_handlers = enable_exception_handlers
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self.enable_messaging = enable_messaging
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self.custom_metrics = custom_metrics or {}
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self.alert_service_class = alert_service_class
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# Initialize logging
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setup_logging(service_name, log_level)
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self.logger = structlog.get_logger()
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# Will be set during app creation
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self.app: Optional[FastAPI] = None
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self.metrics_collector = None
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self.health_manager = None
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self.alert_service = None
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def create_app(self, **fastapi_kwargs) -> FastAPI:
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"""
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Create and configure FastAPI application with standardized setup
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"""
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# Default FastAPI configuration
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default_config = {
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"title": self.app_name,
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"description": self.description,
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"version": self.version,
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"openapi_url": f"{self.api_prefix}/openapi.json",
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"docs_url": f"{self.api_prefix}/docs",
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"redoc_url": f"{self.api_prefix}/redoc",
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}
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# Merge with user-provided config
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config = {**default_config, **fastapi_kwargs}
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# Create FastAPI app
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self.app = FastAPI(**config)
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# Setup metrics BEFORE middleware and lifespan
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if self.enable_metrics:
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self.metrics_collector = setup_metrics_early(self.app, self.service_name)
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# Setup lifespan
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self.app.router.lifespan_context = self._create_lifespan()
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# Setup middleware
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if self.enable_cors:
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self._setup_cors()
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# Setup exception handlers
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if self.enable_exception_handlers:
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self._setup_exception_handlers()
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# Setup health checks
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if self.enable_health_checks:
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self._setup_health_checks()
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# Setup root endpoint
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self._setup_root_endpoint()
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return self.app
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def _create_lifespan(self):
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"""Create lifespan context manager"""
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@asynccontextmanager
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async def lifespan(app: FastAPI):
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# Startup
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self.logger.info(f"Starting {self.service_name}", version=self.version)
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try:
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# Initialize database if provided
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if self.database_manager:
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await self._initialize_database()
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# Setup messaging if enabled
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if self.enable_messaging:
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await self._setup_messaging()
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# Initialize alert service if provided
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if self.alert_service_class:
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await self._initialize_alert_service(app)
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# Register custom metrics if provided
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if self.custom_metrics:
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self.register_custom_metrics(self.custom_metrics)
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# Custom startup logic
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await self.on_startup(app)
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# Mark service as ready
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app.state.ready = True
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self.logger.info(f"{self.service_name} started successfully")
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yield
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except Exception as e:
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self.logger.error(f"Startup failed for {self.service_name}", error=str(e))
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raise
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finally:
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# Shutdown
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self.logger.info(f"Shutting down {self.service_name}")
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try:
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await self.on_shutdown(app)
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# Cleanup alert service if it exists
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if self.alert_service:
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await self._cleanup_alert_service()
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# Cleanup messaging if enabled
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if self.enable_messaging:
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await self._cleanup_messaging()
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if self.database_manager:
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await self._cleanup_database()
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except Exception as e:
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self.logger.error(f"Shutdown error for {self.service_name}", error=str(e))
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return lifespan
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async def on_startup(self, app: FastAPI):
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"""
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Override this method for custom startup logic
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Called after database initialization but before marking as ready
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"""
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pass
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async def on_shutdown(self, app: FastAPI):
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"""
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Override this method for custom shutdown logic
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Called before database cleanup
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"""
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pass
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async def _initialize_database(self):
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"""Initialize database connection"""
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try:
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# Test connection
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if await self.database_manager.test_connection():
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self.logger.info("Database initialized successfully")
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else:
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raise Exception("Database connection test failed")
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except Exception as e:
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self.logger.error("Database initialization failed", error=str(e))
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raise
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async def _cleanup_database(self):
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"""Cleanup database connections"""
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try:
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await self.database_manager.close_connections()
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self.logger.info("Database connections closed")
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except Exception as e:
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self.logger.error("Database cleanup error", error=str(e))
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async def _setup_messaging(self):
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"""Setup messaging service - to be overridden by services that need it"""
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pass
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async def _cleanup_messaging(self):
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"""Cleanup messaging service - to be overridden by services that need it"""
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pass
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async def _initialize_alert_service(self, app: FastAPI):
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"""Initialize alert service - to be overridden by services that need it"""
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pass
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async def _cleanup_alert_service(self):
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"""Cleanup alert service - to be overridden by services that need it"""
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pass
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def _setup_cors(self):
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"""Setup CORS middleware"""
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if self.app is not None:
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self.app.add_middleware(
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CORSMiddleware,
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allow_origins=self.cors_origins,
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allow_credentials=True,
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allow_methods=["*"],
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allow_headers=["*"],
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)
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def _setup_exception_handlers(self):
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"""Setup standard exception handlers"""
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if self.app is not None:
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@self.app.exception_handler(ValueError)
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async def value_error_handler(request: Request, exc: ValueError):
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"""Handle validation errors"""
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return JSONResponse(
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status_code=400,
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content={
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"error": "Validation Error",
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"detail": str(exc),
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"type": "value_error"
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}
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)
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@self.app.exception_handler(Exception)
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async def general_exception_handler(request: Request, exc: Exception):
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"""Handle general exceptions"""
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self.logger.error(
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"Unhandled exception",
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error=str(exc),
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path=request.url.path,
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method=request.method
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)
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# Record error metric if available
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if self.metrics_collector:
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self.metrics_collector.increment_counter("errors_total", labels={"type": "unhandled"})
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return JSONResponse(
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status_code=500,
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content={
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"error": "Internal Server Error",
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"detail": "An unexpected error occurred",
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"type": "internal_error"
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}
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)
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def _setup_health_checks(self):
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"""Setup health check endpoints"""
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self.health_manager = setup_fastapi_health_checks(
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app=self.app,
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service_name=self.service_name,
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version=self.version,
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database_manager=self.database_manager,
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expected_tables=self.expected_tables,
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custom_checks=self.custom_health_checks
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)
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def _setup_root_endpoint(self):
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"""Setup root endpoint with service information"""
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if self.app is not None:
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@self.app.get("/")
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async def root():
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"""Root endpoint with service information"""
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return {
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"service": self.service_name,
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"version": self.version,
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"description": self.description,
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"status": "running",
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"docs_url": f"{self.api_prefix}/docs",
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"health_url": "/health"
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}
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def add_router(self, router: APIRouter, **kwargs: Any):
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"""Convenience method to add routers with default prefix"""
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if self.app is not None:
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prefix = kwargs.get('prefix', self.api_prefix)
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kwargs['prefix'] = prefix
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self.app.include_router(router, **kwargs)
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def register_custom_metrics(self, metrics_config: Dict[str, Dict[str, Any]]):
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"""
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Register custom metrics for the service
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Args:
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metrics_config: Dict with metric name as key and config as value
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Example: {
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"user_registrations": {
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"type": "counter",
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"description": "Total user registrations",
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"labels": ["status"]
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}
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}
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"""
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if not self.metrics_collector:
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self.logger.warning("Metrics collector not available")
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return
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for metric_name, config in metrics_config.items():
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metric_type = config.get("type", "counter")
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description = config.get("description", f"{metric_name} metric")
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labels = config.get("labels", [])
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if metric_type == "counter":
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self.metrics_collector.register_counter(metric_name, description, labels=labels)
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elif metric_type == "histogram":
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self.metrics_collector.register_histogram(metric_name, description, labels=labels)
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else:
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self.logger.warning(f"Unsupported metric type: {metric_type}")
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def run_development_server(self, host: str = "0.0.0.0", port: int = 8000, reload: Optional[bool] = None):
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"""
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Run development server with uvicorn
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"""
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import uvicorn
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if reload is None:
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reload = os.getenv("RELOAD", "false").lower() == "true"
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uvicorn.run(
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f"{self.__module__}:app",
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host=host,
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port=port,
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reload=reload,
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log_level="info"
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)
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class StandardFastAPIService(BaseFastAPIService):
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"""
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Standard service implementation for most microservices
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Provides additional common patterns for services with database and standard endpoints
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"""
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def __init__(self, **kwargs: Any):
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super().__init__(**kwargs)
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def setup_standard_endpoints(self):
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"""Setup standard service endpoints"""
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if self.app is not None:
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@self.app.get(f"{self.api_prefix}/info")
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async def service_info():
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"""Service information endpoint"""
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return {
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"service": self.service_name,
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"version": self.version,
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"description": self.description,
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"api_version": "v1",
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"environment": os.getenv("ENVIRONMENT", "development"),
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"features": self.get_service_features()
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}
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def get_service_features(self) -> List[str]:
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"""
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Override this method to return service-specific features
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"""
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return ["health_checks", "metrics", "standardized_api"]
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class MessageProcessorService(BaseFastAPIService):
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"""
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Service implementation for message processing services
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Provides patterns for background processing services
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"""
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def __init__(self, **kwargs: Any):
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# Message processors typically don't need CORS or full API setup
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kwargs.setdefault('enable_cors', False)
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kwargs.setdefault('api_prefix', '/api/v1')
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super().__init__(**kwargs)
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async def on_startup(self, app: FastAPI):
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"""Initialize message processing components"""
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await super().on_startup(app)
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await self.setup_message_processing()
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async def on_shutdown(self, app: FastAPI):
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"""Cleanup message processing components"""
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await self.cleanup_message_processing()
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await super().on_shutdown(app)
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async def setup_message_processing(self):
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"""Override this method to setup message processing"""
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pass
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async def cleanup_message_processing(self):
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"""Override this method to cleanup message processing"""
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pass |