From 2c9f2a30f7af905eac384016137e5fb5cf2efd7e Mon Sep 17 00:00:00 2001
From: Zev Averbach <zev@averba.ch>
Date: Fri, 11 Aug 2023 08:01:18 +0300
Subject: [PATCH] fixed first algo so it adds as many tokens as needed after
 more than one time period has passed

---
 my_limiter/algos.py  | 15 ++++++++++-----
 my_limiter/config.py |  1 -
 my_limiter/wsgi.py   | 17 +++++++++++++++++
 3 files changed, 27 insertions(+), 6 deletions(-)
 delete mode 100644 my_limiter/config.py

diff --git a/my_limiter/algos.py b/my_limiter/algos.py
index f7b0642..1afb7c6 100644
--- a/my_limiter/algos.py
+++ b/my_limiter/algos.py
@@ -9,7 +9,7 @@ class TooManyRequests(Exception):
     pass
 
 
-def token_bucket(ip: str):
+def token_bucket(ip: str) -> str:
     """
     Tokens are put in the bucket at preset rates periodically. 
     Once the bucket is full, no more tokens are added. 
@@ -17,17 +17,22 @@ def token_bucket(ip: str):
     """
     REFILL_EVERY_SECONDS = TIME_INTERVAL_SECONDS
     NUM_TOKENS_TO_REFILL = 4
-    MAX_CAPACITY = 4
+    MAX_CAPACITY = 8
 
     entry = TOKEN_BUCKET.get(ip)
 
     if entry is None:
-        TOKEN_BUCKET[ip] = {'tokens': 4, 'last_refilled': dt.datetime.now().timestamp()}
+        TOKEN_BUCKET[ip] = {'tokens': MAX_CAPACITY, 'last_refilled': dt.datetime.now().timestamp()}
     else:
-        if dt.datetime.now().timestamp() >= entry['last_refilled'] + REFILL_EVERY_SECONDS:
+        last_refilled = entry['last_refilled']
+        now = dt.datetime.now().timestamp() 
+        if now >= last_refilled + REFILL_EVERY_SECONDS:
+            num_tokens_to_refill = int((now - last_refilled) // REFILL_EVERY_SECONDS * NUM_TOKENS_TO_REFILL)
             entry['last_refilled'] = dt.datetime.now().timestamp()
-            entry['tokens'] = min(entry['tokens'] + NUM_TOKENS_TO_REFILL, MAX_CAPACITY)
+            entry['tokens'] = min(entry['tokens'] + num_tokens_to_refill, MAX_CAPACITY)
+
     left = TOKEN_BUCKET[ip]['tokens']
     if left == 0:
         raise TooManyRequests
+
     TOKEN_BUCKET[ip]['tokens'] -= 1
\ No newline at end of file
diff --git a/my_limiter/config.py b/my_limiter/config.py
deleted file mode 100644
index 8b13789..0000000
--- a/my_limiter/config.py
+++ /dev/null
@@ -1 +0,0 @@
-
diff --git a/my_limiter/wsgi.py b/my_limiter/wsgi.py
index d139e82..61f01f3 100644
--- a/my_limiter/wsgi.py
+++ b/my_limiter/wsgi.py
@@ -1,3 +1,20 @@
+"""
+TODO: implement leaky bucket
+  - in-app
+    - [x] in-memory
+    - [ ] redis
+    - [ ] redis cluster
+    - [ ] Flask middleware - https://flask.palletsprojects.com/en/2.1.x/quickstart/#hooking-in-wsgi-middleware
+  - [ ] NGINX - https://leandromoreira.com/2019/01/25/how-to-build-a-distributed-throttling-system-with-nginx-lua-redis/
+              - https://www.nginx.com/blog/rate-limiting-nginx/
+  - [ ] AWS API Gateway
+  - [ ] HAProxy Stick Tables  - https://www.haproxy.com/blog/introduction-to-haproxy-stick-tables
+  - [ ] Cloudflare (Spectrum?)
+TODO: implement fixed window counter
+TODO: implement sliding window log
+TODO: implement sliding window counter 
+TODO: use session IDs instead of IP address
+"""
 import flask as f
 
 from . import algos