fix: add cache to prevent Binance rate limit (rates 3s, history/stats 60s)

backend/main.py

@@ -2,7 +2,7 @@ from fastapi import FastAPI, HTTPException
 from fastapi.middleware.cors import CORSMiddleware
 import httpx
 from datetime import datetime, timedelta
-import asyncio
+import asyncio, time
 
 app = FastAPI(title="Arbitrage Engine API")
 
@@ -16,6 +16,18 @@ app.add_middleware(
 BINANCE_FAPI = "https://fapi.binance.com/fapi/v1"
 SYMBOLS = ["BTCUSDT", "ETHUSDT"]
 
+# 简单内存缓存（history/stats 60秒，rates 3秒）
+_cache: dict = {}
+
+def get_cache(key: str, ttl: int):
+    entry = _cache.get(key)
+    if entry and time.time() - entry["ts"] < ttl:
+        return entry["data"]
+    return None
+
+def set_cache(key: str, data):
+    _cache[key] = {"ts": time.time(), "data": data}
+
 
 @app.get("/api/health")
 async def health():
@@ -24,10 +36,11 @@ async def health():
 
 @app.get("/api/rates")
 async def get_rates():
+    cached = get_cache("rates", 3)
+    if cached: return cached
     async with httpx.AsyncClient(timeout=10) as client:
         tasks = [client.get(f"{BINANCE_FAPI}/premiumIndex", params={"symbol": s}) for s in SYMBOLS]
         responses = await asyncio.gather(*tasks)
-
     result = {}
     for sym, resp in zip(SYMBOLS, responses):
         if resp.status_code != 200:
@@ -42,55 +55,50 @@ async def get_rates():
             "nextFundingTime": data["nextFundingTime"],
             "timestamp": data["time"],
         }
+    set_cache("rates", result)
     return result
 
 
 @app.get("/api/history")
 async def get_history():
+    cached = get_cache("history", 60)
+    if cached: return cached
     end_time = int(datetime.utcnow().timestamp() * 1000)
     start_time = int((datetime.utcnow() - timedelta(days=7)).timestamp() * 1000)
-
     async with httpx.AsyncClient(timeout=15) as client:
         tasks = [
-            client.get(
+            client.get(f"{BINANCE_FAPI}/fundingRate",
-                f"{BINANCE_FAPI}/fundingRate",
+                params={"symbol": s, "startTime": start_time, "endTime": end_time, "limit": 1000})
-                params={"symbol": s, "startTime": start_time, "endTime": end_time, "limit": 1000},
-            )
             for s in SYMBOLS
         ]
         responses = await asyncio.gather(*tasks)
-
     result = {}
     for sym, resp in zip(SYMBOLS, responses):
         if resp.status_code != 200:
             raise HTTPException(status_code=502, detail=f"Binance history error for {sym}")
         key = sym.replace("USDT", "")
         result[key] = [
-            {
+            {"fundingTime": item["fundingTime"], "fundingRate": float(item["fundingRate"]),
-                "fundingTime": item["fundingTime"],
+             "timestamp": datetime.utcfromtimestamp(item["fundingTime"] / 1000).isoformat()}
-                "fundingRate": float(item["fundingRate"]),
-                "timestamp": datetime.utcfromtimestamp(item["fundingTime"] / 1000).isoformat(),
-            }
             for item in resp.json()
         ]
+    set_cache("history", result)
     return result
 
 
 @app.get("/api/stats")
 async def get_stats():
+    cached = get_cache("stats", 60)
+    if cached: return cached
     end_time = int(datetime.utcnow().timestamp() * 1000)
     start_time = int((datetime.utcnow() - timedelta(days=7)).timestamp() * 1000)
-
     async with httpx.AsyncClient(timeout=15) as client:
         tasks = [
-            client.get(
+            client.get(f"{BINANCE_FAPI}/fundingRate",
-                f"{BINANCE_FAPI}/fundingRate",
+                params={"symbol": s, "startTime": start_time, "endTime": end_time, "limit": 1000})
-                params={"symbol": s, "startTime": start_time, "endTime": end_time, "limit": 1000},
-            )
             for s in SYMBOLS
         ]
         responses = await asyncio.gather(*tasks)
-
     stats = {}
     for sym, resp in zip(SYMBOLS, responses):
         if resp.status_code != 200:
@@ -101,14 +109,12 @@ async def get_stats():
             stats[key] = {"mean7d": 0, "annualized": 0, "count": 0}
             continue
         mean = sum(rates) / len(rates)
-        annualized = mean * 3 * 365 * 100  # 3 settlements/day * 365 days * %
+        annualized = mean * 3 * 365 * 100
         stats[key] = {
-            "mean7d": round(mean * 100, 6),       # as percent
+            "mean7d": round(mean * 100, 6),
-            "annualized": round(annualized, 2),   # as percent
+            "annualized": round(annualized, 2),
             "count": len(rates),
         }
-
-    # 50-50 combo
     btc_ann = stats.get("BTC", {}).get("annualized", 0)
     eth_ann = stats.get("ETH", {}).get("annualized", 0)
     btc_mean = stats.get("BTC", {}).get("mean7d", 0)
@@ -117,5 +123,5 @@ async def get_stats():
         "mean7d": round((btc_mean + eth_mean) / 2, 6),
         "annualized": round((btc_ann + eth_ann) / 2, 2),
     }
-
+    set_cache("stats", stats)
     return stats