Initialise redis connection for Fastapi limiter

backend/main.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 from http import HTTPStatus
+from math import ceil
 from pathlib import Path
 from typing import Optional
 
@@ -7,6 +8,8 @@ import alembic.command
 import alembic.config
 import fastapi
 import pydantic
+import redis.asyncio as redis
+from fastapi_limiter import FastAPILimiter
 from loguru import logger
 from oasst_backend.api.deps import get_dummy_api_client
 from oasst_backend.api.v1.api import api_router
@@ -63,6 +66,29 @@ if settings.UPDATE_ALEMBIC:
             logger.exception("Alembic upgrade failed on startup")
 
 
+if settings.RATE_LIMIT:
+
+    @app.on_event("startup")
+    async def connect_redis():
+        async def http_callback(request: fastapi.Request, response: fastapi.Response, pexpire: int):
+            """Error callback function when too many requests"""
+            expire = ceil(pexpire / 1000)
+            raise OasstError(
+                f"Too Many Requests. Retry After {expire} seconds.",
+                OasstErrorCode.TOO_MANY_REQUESTS,
+                HTTPStatus.TOO_MANY_REQUESTS,
+            )
+
+        try:
+            redis_client = redis.from_url(
+                f"redis://{settings.REDIS_HOST}:{settings.REDIS_PORT}/0", encoding="utf-8", decode_responses=True
+            )
+            logger.info(f"Connected to {redis_client=}")
+            await FastAPILimiter.init(redis_client, http_callback=http_callback)
+        except Exception:
+            logger.exception("Failed to establish Redis connection")
+
+
 if settings.DEBUG_USE_SEED_DATA:
 
     @app.on_event("startup")

backend/oasst_backend/config.py

@@ -15,6 +15,10 @@ class Settings(BaseSettings):
     POSTGRES_DB: str = "postgres"
     DATABASE_URI: Optional[PostgresDsn] = None
 
+    RATE_LIMIT: bool = True
+    REDIS_HOST: str = "localhost"
+    REDIS_PORT: str = "6379"
+
     DEBUG_ALLOW_ANY_API_KEY: bool = False
     DEBUG_SKIP_API_KEY_CHECK: bool = False
     DEBUG_USE_SEED_DATA: bool = False