Feature/ratelimiter update (#330)

* updated request_is_limited algorithm

openaq_api/openaq_api/middleware.py

@@ -1,6 +1,6 @@
 import logging
 import time
-from datetime import timedelta
+from datetime import timedelta, datetime
 from os import environ
 from fastapi import Response, status
 from fastapi.responses import JSONResponse
@@ -133,19 +133,16 @@ def __init__(
         self.rate_time = rate_time
 
     async def request_is_limited(self, key: str, limit: int, request: Request) -> bool:
-        if await self.redis_client.set(key, limit, nx=True):
-            await self.redis_client.expire(key, int(self.rate_time.total_seconds()))
-        count = await self.redis_client.get(key)
-        if count in ("-1", "-2"):
-            logger.error(
-                RedisErrorLog(
-                    detail=f"redis has an invalid value for limit: {count} for key: {key}"
-                )
-            )
-        if count and int(count) > 0:
-            request.state.counter = await self.redis_client.decrby(key, 1)
-            return False
-        return True
+        now = datetime.now()
+        k = f"{key}:{now.year}{now.month}{now.day}{now.hour}{now.minute}"
+        value = await self.redis_client.get(k)
+        if value is None or int(value) < limit:
+            async with self.redis_client.pipeline() as pipe:
+                [incr, _] = await pipe.incr(k).expire(k, 60).execute()
+                request.state.counter = limit - incr
+                return False
+        else:
+            return True
 
     async def check_valid_key(self, key: str) -> bool:
         if await self.redis_client.sismember("keys", key):
@@ -214,11 +211,11 @@ async def dispatch(
         response.headers["RateLimit-Reset"] = str(ttl)
         rate_time_seconds = int(self.rate_time.total_seconds())
         if auth:
-            response.headers[
-                "RateLimit-Policy"
-            ] = f"{self.rate_amount_key};w={rate_time_seconds}"
+            response.headers["RateLimit-Policy"] = (
+                f"{self.rate_amount_key};w={rate_time_seconds}"
+            )
         else:
-            response.headers[
-                "RateLimit-Policy"
-            ] = f"{self.rate_amount};w={rate_time_seconds}"
+            response.headers["RateLimit-Policy"] = (
+                f"{self.rate_amount};w={rate_time_seconds}"
+            )
         return response