fix: 대규모 Alpaca 백필 시 uvicorn 이벤트 루프 포화 방지

동시 Alpaca intraday 요청이 50개 이상 쌓이면 BaseHTTPMiddleware의
task 스케줄링 오버헤드로 이벤트 루프가 응답불능 상태가 되는 현상 수정.

- alpaca.py: _INTRADAY_SEMAPHORE(10) 추가 — /intraday, /intraday/today
  양쪽 핸들러를 감쌈. 11번째 이후 요청은 세마포어 대기(비용 없음)
- docker-compose.yml: --limit-concurrency 100 추가 — 100개 초과 시
  uvicorn이 503 반환, health 엔드포인트 보호

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/api/v1/endpoints/alpaca.py

@@ -2,6 +2,7 @@
 Alpaca Market Data endpoints — standalone price data via Alpaca API
 """
 
+import asyncio
 from datetime import date, datetime, timezone, timedelta
 from typing import Optional
 from zoneinfo import ZoneInfo
@@ -11,6 +12,11 @@ from fastapi import APIRouter, HTTPException, Query
 _ET = ZoneInfo("America/New_York")
 _MARKET_CLOSE_HOUR = 16  # 4:00 PM ET
 
+# Limit concurrent Alpaca intraday processing to prevent event-loop saturation
+# under bulk backfill workloads. Callers beyond this limit wait on the semaphore
+# (cheap asyncio wait) rather than flooding httpx connections and DB sessions.
+_INTRADAY_SEMAPHORE = asyncio.Semaphore(10)
+
 
 def _market_closed_for(d: date) -> bool:
     """Return True if the US equity market session for date d has ended."""
@@ -120,21 +126,22 @@ async def get_alpaca_intraday_multi(
     start_dt = datetime.combine(_start, datetime.min.time()).replace(tzinfo=timezone.utc)
     end_dt = datetime.combine(_end, datetime.max.time()).replace(tzinfo=timezone.utc)
 
-    try:
-        data = await svc.get_or_fetch_multi_bars(
-            symbols, start_dt, end_dt, interval, force_refresh, feed="sip"
-        )
-    except Exception as e:
-        err = str(e)
-        detail = f"Alpaca API error: {err}"
-        if "502" in err or "Bad Gateway" in err:
-            detail = (
-                f"Alpaca 502 Bad Gateway — 요청당 심볼 수 초과 가능성. "
-                f"내부 배치 크기: 100개/요청. 원인: {err}"
+    async with _INTRADAY_SEMAPHORE:
+        try:
+            data = await svc.get_or_fetch_multi_bars(
+                symbols, start_dt, end_dt, interval, force_refresh, feed="sip"
             )
-        raise HTTPException(status_code=502, detail=detail)
-    finally:
-        await svc.client.close()
+        except Exception as e:
+            err = str(e)
+            detail = f"Alpaca API error: {err}"
+            if "502" in err or "Bad Gateway" in err:
+                detail = (
+                    f"Alpaca 502 Bad Gateway — 요청당 심볼 수 초과 가능성. "
+                    f"내부 배치 크기: 100개/요청. 원인: {err}"
+                )
+            raise HTTPException(status_code=502, detail=detail)
+        finally:
+            await svc.client.close()
 
     bars = {
         ticker: [
@@ -193,21 +200,22 @@ async def get_alpaca_intraday_today(
     start_dt = datetime.combine(today, datetime.min.time()).replace(tzinfo=timezone.utc)
     end_dt = datetime.combine(today, datetime.max.time()).replace(tzinfo=timezone.utc)
 
-    try:
-        data = await svc.get_or_fetch_multi_bars(
-            symbols, start_dt, end_dt, interval, force_refresh=True, feed="iex"
-        )
-    except Exception as e:
-        err = str(e)
-        detail = f"Alpaca API error: {err}"
-        if "502" in err or "Bad Gateway" in err:
-            detail = (
-                f"Alpaca 502 Bad Gateway — 요청당 심볼 수 초과 가능성. "
-                f"내부 배치 크기: 100개/요청. 원인: {err}"
+    async with _INTRADAY_SEMAPHORE:
+        try:
+            data = await svc.get_or_fetch_multi_bars(
+                symbols, start_dt, end_dt, interval, force_refresh=True, feed="iex"
             )
-        raise HTTPException(status_code=502, detail=detail)
-    finally:
-        await svc.client.close()
+        except Exception as e:
+            err = str(e)
+            detail = f"Alpaca API error: {err}"
+            if "502" in err or "Bad Gateway" in err:
+                detail = (
+                    f"Alpaca 502 Bad Gateway — 요청당 심볼 수 초과 가능성. "
+                    f"내부 배치 크기: 100개/요청. 원인: {err}"
+                )
+            raise HTTPException(status_code=502, detail=detail)
+        finally:
+            await svc.client.close()
 
     bars = {
         ticker: [

docker-compose.yml

@@ -66,7 +66,7 @@ services:
       - ./yfinance_plus:/app/yfinance_plus  # Mount yfinance_plus for development
       - ./data:/app/data  # For data files
     restart: unless-stopped
-    command: ["python", "-m", "uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "18000", "--reload"]
+    command: ["python", "-m", "uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "18000", "--reload", "--limit-concurrency", "100"]
 
   # Frontend Application
   frontend: