From bcd35114151541c6588d7a90bbdc0f432900c661 Mon Sep 17 00:00:00 2001
From: Adarsh Gautam <232441988+adarsh-gautam-sys@users.noreply.github.com>
Date: Sun, 21 Jun 2026 21:23:35 +0530
Subject: [PATCH] fix: resolve #99 - consolidate duplicate FastAPI instances
 and metrics endpoint

---
 app/main.py | 114 +++++++++++++++++++++++++++++-----------------------
 1 file changed, 63 insertions(+), 51 deletions(-)

diff --git a/app/main.py b/app/main.py
index eeed26e..c0dcce7 100644
--- a/app/main.py
+++ b/app/main.py
@@ -1,64 +1,35 @@
-from fastapi import FastAPI, Depends
+import logging
+from fastapi import FastAPI, Depends, HTTPException
 from fastapi.middleware.cors import CORSMiddleware
+from prometheus_client import generate_latest
+from starlette.responses import Response
 
 from app.core.config import settings
 from app.core.dependencies import get_current_user
-
 from app.api.v1.auth import router as auth_router
 from app.api.v1.tenants import router as tenants_router
 from app.api.v1.document import router as document_router
 from app.api.v1.rag import router as rag_router
-from fastapi import FastAPI
-from prometheus_client import generate_latest
-from starlette.responses import Response
-from core.middleware import MetricsMiddleware
-from core.middleware_logging import LoggingMiddleware
-from core.rate_limit import init_redis
-from fastapi import Depends, HTTPException
-from core.dependencies import get_current_user
-
-@app.get("/metrics")
-def metrics(user=Depends(get_current_user)):
-    if user.get("sub") != "admin":
-        raise HTTPException(status_code=403, detail="Not allowed")
-
-    return Response(generate_latest(), media_type="text/plain")
-
-
-
-@app.on_event("startup")
-async def startup():
-    await init_redis()
-
-
-app.add_middleware(LoggingMiddleware)
-
-
-app = FastAPI()
-
-app.add_middleware(MetricsMiddleware)
-
-@app.get("/metrics")
-def metrics():
-    return Response(generate_latest(), media_type="text/plain")
-
 
+from app.middleware.middleware import MetricsMiddleware
+from app.middleware.middleware_logging import LoggingMiddleware
+from app.reliability.rate_limit import init_redis
 from app.db.init_db import init_db
+from app.observability.tracing import setup_tracing
 
-# ===============================
-# Create FastAPI App
-# ===============================
-app = FastAPI(title=settings.APP_NAME)
+logger = logging.getLogger(__name__)
 
 # ===============================
-# Initialize DB
+# Create FastAPI App
 # ===============================
-@app.on_event("startup")
-def startup_event():
-    init_db()
+app = FastAPI(
+    title=settings.APP_NAME,
+    docs_url="/docs",
+    redoc_url="/redoc",
+)
 
 # ===============================
-# CORS (FINAL & CORRECT)
+# CORS Middleware
 # ===============================
 app.add_middleware(
     CORSMiddleware,
@@ -72,16 +43,49 @@ def startup_event():
     allow_headers=["*"],
 )
 
+# ===============================
+# Custom Middlewares
+# ===============================
+app.add_middleware(MetricsMiddleware)
+app.add_middleware(LoggingMiddleware)
+
 # ===============================
 # Routers
 # ===============================
-app.include_router(auth_router)
-app.include_router(tenants_router)
-app.include_router(document_router)
-app.include_router(rag_router)
+app.include_router(auth_router, prefix="/api/v1/auth", tags=["auth"])
+app.include_router(tenants_router, prefix="/api/v1/tenants", tags=["tenants"])
+app.include_router(document_router, prefix="/api/v1/documents", tags=["documents"])
+app.include_router(rag_router, prefix="/api/v1/rag", tags=["rag"])
+
+# ===============================
+# Startup Event (Reliability & Observability)
+# ===============================
+@app.on_event("startup")
+async def startup_event() -> None:
+    """
+    Application startup handler.
+    Initializes the database and Redis connection pool.
+    Raises RuntimeError to abort startup if the database is unavailable,
+    ensuring the application never starts in a broken state.
+    """
+    try:
+        init_db()
+        logger.info("Database initialized successfully.")
+    except Exception as exc:
+        logger.critical("Database initialization failed: %s", exc, exc_info=True)
+        raise RuntimeError(
+            f"Startup aborted — database unavailable: {exc}"
+        ) from exc
+
+    try:
+        await init_redis()
+        logger.info("Redis connection pool ready.")
+    except Exception as exc:
+        logger.warning("Redis initialization failed: %s", exc, exc_info=True)
+        # Redis failure is non-fatal (degraded mode); log and continue.
 
 # ===============================
-# Health Routes
+# Health & Metrics Routes
 # ===============================
 @app.get("/")
 def root():
@@ -98,6 +102,14 @@ def protected(user=Depends(get_current_user)):
         "user": user,
     }
 
-from core.tracing import setup_tracing
+@app.get("/metrics", include_in_schema=False)
+def metrics(user=Depends(get_current_user)):
+    """Prometheus metrics endpoint — admin only."""
+    if user.get("sub") != "admin":
+        raise HTTPException(status_code=403, detail="Admin access required")
+    return Response(generate_latest(), media_type="text/plain")
 
+# ===============================
+# OpenTelemetry Tracing
+# ===============================
 setup_tracing()
\ No newline at end of file