Add limiter storage to memcache

Author: Aadesh-Baral

backend/__init__.py

@@ -2,7 +2,7 @@
 import os
 from logging.handlers import RotatingFileHandler
 
-from flask import Flask, redirect, make_response, jsonify
+from flask import Flask, redirect
 from flask_cors import CORS
 from flask_migrate import Migrate
 from flask_oauthlib.client import OAuth
@@ -37,8 +37,11 @@ def format_url(endpoint):
 migrate = Migrate()
 mail = Mail()
 oauth = OAuth()
-limiter = Limiter(key_func=get_remote_address, headers_enabled=True)
-
+limiter = Limiter(
+    storage_uri=EnvironmentConfig.MEMCACHED_URI,
+    key_func=get_remote_address,
+    headers_enabled=True,
+)
 osm = oauth.remote_app("osm", app_key="OSM_OAUTH_SETTINGS")
 
 # Import all models so that they are registered with SQLAlchemy
@@ -130,7 +133,12 @@ def add_api_endpoints(app):
             "SubCode": "RateLimitExceeded",
             "message": "You have exceeded the rate limit. Please try again later.",
             "status": 429,
-        }
+        },
+        "MemcacheUnexpectedCloseError": {
+            "SubCode": "MemcacheUnexpectedCloseError",
+            "message": "Connection to Memcache server lost.",
+            "status": 500,
+        },
     }
     api = Api(app, errors=rate_limit_error)
 

backend/config.py

@@ -109,6 +109,13 @@ class EnvironmentConfig:
     DEFAULT_RATE_LIMIT_THRESHOLD = os.getenv(
         "TM_API_RATE_LIMIT_THRESHOLD", "100 per hour"
     )
+    # Memcache configuration
+    MEMCACHED_PORT = os.getenv("TM_MEMCACHE_PORT", None)
+    MEMCACHED_HOST = os.getenv("TM_MEMCACHE_HOST", None)
+    if MEMCACHED_PORT and MEMCACHED_HOST:
+        MEMCACHED_URI = f"memcached://{MEMCACHED_HOST}:{MEMCACHED_PORT}"
+    else:
+        MEMCACHED_URI = None
 
     # Languages offered by the Tasking Manager
     # Please note that there must be exactly the same number of Codes as languages.

requirements.txt

@@ -36,6 +36,7 @@ Mako==1.1.3
 markdown==3.3.3
 MarkupSafe==1.1.1
 mccabe==0.6.1
+pymemcache==3.5.2
 newrelic==5.22.1.152
 nose==1.3.7
 oauthlib==2.0.2