kami_spider_monorepo/main.py

"""
Main FastAPI application entry point.
Bootstraps the application with middleware, routers, and lifecycle handlers.
"""

from contextlib import asynccontextmanager
from fastapi import FastAPI
from fastapi.responses import ORJSONResponse
from fastapi.middleware.cors import CORSMiddleware
from core.config import settings
from core.database import create_db_and_tables, close_database_connection
from core.redis import init_redis, close_redis_connection
from core.responses import ERROR_RESPONSES
from observability.tracing import init_tracing, instrument_app, shutdown_tracing
from observability.logging import setup_logging, get_logger
from middleware.trace_context import TraceContextMiddleware
from middleware.logging import RequestLoggingMiddleware
from middleware.error_handler import register_exception_handlers
from apps.app_a.router import router as app_a_router
from apps.app_b.router import router as app_b_router

logger = get_logger(__name__)


@asynccontextmanager
async def lifespan(app: FastAPI):
    """
    Application lifespan manager.
    
    Handles startup and shutdown events.
    """
    # Startup
    logger.info("Starting application...")
    
    # Setup logging
    setup_logging()
    logger.info(f"Logging configured: level={settings.log_level}")
    
    # Initialize OpenTelemetry
    if settings.otel_enabled:
        init_tracing()
        instrument_app(app)
        logger.info(f"OpenTelemetry initialized: endpoint={settings.otel_exporter_endpoint}")
    
    # Initialize Redis
    await init_redis()
    logger.info(f"Redis initialized: {settings.redis_host}:{settings.redis_port}")
    
    # Create database tables (development only)
    if settings.is_development:
        await create_db_and_tables()
        logger.info("Database tables created")
    
    logger.info(f"Application started: environment={settings.environment}")
    
    yield
    
    # Shutdown
    logger.info("Shutting down application...")
    
    # Close Redis connection
    await close_redis_connection()
    logger.info("Redis connection closed")
    
    # Close database connection
    await close_database_connection()
    logger.info("Database connection closed")
    
    # Shutdown OpenTelemetry
    if settings.otel_enabled:
        await shutdown_tracing()
        logger.info("OpenTelemetry shutdown")
    
    logger.info("Application shutdown complete")


# Create FastAPI application
app = FastAPI(
    title=settings.app_name,
    description="A stateless, production-ready FastAPI web service platform",
    version="0.1.0",
    debug=settings.debug,
    lifespan=lifespan,
    docs_url="/docs",
    redoc_url="/redoc",
    openapi_url="/openapi.json",
    default_response_class=ORJSONResponse,  # Use orjson for better performance
)

# Add CORS middleware
if settings.cors_enabled:
    app.add_middleware(
        CORSMiddleware,
        allow_origins=settings.cors_allow_origins,
        allow_credentials=settings.cors_allow_credentials,
        allow_methods=settings.cors_allow_methods,
        allow_headers=settings.cors_allow_headers,
    )

# Add custom middleware (order matters: last added = first executed)
app.add_middleware(RequestLoggingMiddleware)
app.add_middleware(TraceContextMiddleware)

# Register exception handlers
register_exception_handlers(app)

# Include application routers
app.include_router(app_a_router)
app.include_router(app_b_router)


# Health check endpoint
@app.get(
    "/health",
    tags=["Health"],
    summary="Health check",
    description="Check the health status of the application and its dependencies",
    responses={
        200: {"description": "Service is healthy"},
        500: ERROR_RESPONSES[500],
        503: ERROR_RESPONSES[503],
    }
)
async def health_check():
    """
    Health check endpoint.
    
    Returns health status of the application and its components.
    """
    from core.database import check_database_connection
    from core.redis import check_redis_connection
    
    # Check database
    db_healthy = await check_database_connection()
    
    # Check Redis
    redis_healthy = await check_redis_connection()
    
    # Overall health
    healthy = db_healthy and redis_healthy
    
    return {
        "status": "healthy" if healthy else "unhealthy",
        "components": {
            "api": "healthy",
            "database": "healthy" if db_healthy else "unhealthy",
            "redis": "healthy" if redis_healthy else "unhealthy",
        },
        "environment": settings.environment,
        "version": "0.1.0",
    }


# Root endpoint
@app.get(
    "/",
    tags=["Root"],
    summary="Root endpoint",
    description="Get API information",
    responses={
        200: {"description": "API information retrieved successfully"},
    }
)
async def root():
    """Root endpoint with API information."""
    return {
        "name": settings.app_name,
        "version": "0.1.0",
        "environment": settings.environment,
        "docs": "/docs",
        "health": "/health",
    }


if __name__ == "__main__":
    import uvicorn
    
    uvicorn.run(
        "main:app",
        host=settings.host,
        port=settings.port,
        reload=settings.debug,
        log_level=settings.log_level.lower(),
    )