looking at rate-limiting implementations

rate_limiters/.gitignore

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+# Python-generated files
+__pycache__/
+.venv
+.ruff_cache
+.pytest_cache

rate_limiters/.python-version

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+3.11

rate_limiters/fixed_window.py

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+import threading
+from datetime import datetime, timedelta
+from time import sleep
+
+
+class FixedWindowLimiter:
+    def __init__(self, window_size: int, window_duration: int):
+        self.window_size = window_size
+        self.window_duration = window_duration
+        self.count = 0
+        self.last_reset_time = datetime.now()
+        self._lock = threading.Lock()
+
+    def __enter__(self):
+        with self._lock:
+            if datetime.now() - self.last_reset_time > timedelta(
+                seconds=self.window_duration
+            ):
+                self.count = 0
+                self.last_reset_time = datetime.now()
+            if self.count < self.window_size:
+                self.count += 1
+                print("ALLOWED")
+                return self
+            else:
+                raise RuntimeError("Rate exceeded!")
+
+    def __exit__(self, exc_type, exc_value, exc_traceback):
+        return False
+
+
+def make_requests(number: int, limiter: FixedWindowLimiter) -> None:
+    for i in range(1, number):
+        try:
+            with limiter as lim:
+                print(f"PRE-BUDGET: {lim.window_size - lim.count}")
+                print("REQUEST MADE!")
+        except RuntimeError:
+            print("Request limit reached!")
+            sleep(0.5)
+
+# lim_1 = FixedWindowLimiter(window_duration=10, window_size=10)
+
+# make_requests(100, lim_1)

rate_limiters/main.py

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+def main():
+    print("Hello from rate-limiters!")
+
+
+if __name__ == "__main__":
+    main()

rate_limiters/pyproject.toml

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+[project]
+name = "rate-limiters"
+version = "0.1.0"
+description = "Add your description here"
+readme = "README.md"
+requires-python = ">=3.11"
+dependencies = [
+    "pytest>=9.0.3",
+]

rate_limiters/tests/test_fixed_window.py

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+import pytest
+
+from fixed_window import FixedWindowLimiter
+
+def test_limit_respected():
+    limiter = FixedWindowLimiter(10, 10)
+    try:
+        for i in range(9):
+            with limiter:
+                pass
+    except RuntimeError as e:
+        assert False, f"Limiter raised an exception -> {e}"
+    
+def test_limit_enforced():
+    limiter = FixedWindowLimiter(10, 10)
+    with pytest.raises(RuntimeError) as e:
+        for i in range(11):
+            with limiter:
+                pass
+    assert "Rate exceeded" in str(e.value)

rate_limiters/tests/test_token_bucket.py

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+import pytest
+from time import sleep
+from token_bucket import TokenBucketLimiter, RateLimitExceeded
+
+def test_limit_respected() -> None:
+    limiter = TokenBucketLimiter(10, 10)
+
+    try:
+        for i in range(30):
+            with limiter:
+                sleep(0.1)
+    except RateLimitExceeded:
+        assert False, "Rate limit exceeded!"
+
+
+def test_limit_exceeded() -> None:
+    limiter = TokenBucketLimiter(10, 10)
+
+    with pytest.raises(RateLimitExceeded) as e:
+        for i in range(20):
+            with limiter:
+                continue
+    
+    assert "Rate exceeded" in str(e.value)
+

rate_limiters/token_bucket.py

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+import threading
+from time import sleep, time
+
+
+class RateLimiterException(Exception):
+    pass
+
+
+class RateLimitExceeded(RateLimiterException):
+    def __init__(self, retry_after: float, current_tokens: float):
+        self.retry_after = retry_after
+        self.current_tokens = current_tokens
+        super().__init__(f"Rate exceeded! Retry after {retry_after:.2f} seconds.")
+
+
+class TokenBucketLimiter:
+    def __init__(self, capacity: int, refill_rate: int):
+        self.capacity = float(capacity)
+        self.refill_rate = float(refill_rate)
+        self.tokens = float(capacity)
+        self.last_refill_time = time()
+        self._lock = threading.Lock()
+
+    def __enter__(self):
+        with self._lock:
+            now = time()
+
+            elapsed = now - self.last_refill_time
+            new_tokens = elapsed * self.refill_rate
+
+            self.tokens = min(self.tokens + new_tokens, self.capacity)
+            self.last_refill_time = time()
+
+            if self.tokens < 1:
+                retry_after = (1 - self.tokens) / self.refill_rate
+                raise RateLimitExceeded(retry_after, self.tokens)
+
+            self.tokens -= 1
+            return self
+
+    def __exit__(self, exc_type, exc_value, exc_traceback) -> bool:
+        return False
+
+
+def make_requests(number: int, limiter: TokenBucketLimiter) -> None:
+    start_time = time()
+
+    successful = 0
+    rate_limited = 0
+    failed = 0
+
+    print(f"Starting request cycle with {number} requests...")
+
+    for i in range(1, number):
+        try:
+            with limiter:
+                successful += 1
+        except RateLimitExceeded as e:
+            rate_limited += 1
+            sleep(e.retry_after)
+            try:
+                with limiter:
+                    successful += 1
+            except RuntimeError:
+                failed += 1
+                print("Retry failed! Request limit reached!")
+
+    end_time = time()
+
+    execution_time = end_time - start_time
+    effective_rate = number / execution_time
+
+    print(
+        f"Results: \n\nSuccessfull: {successful}\nRate limited: {rate_limited}\nFailed: {failed}\n"
+    )
+    print(
+        f"Total execution time: {execution_time:.2f}\nEffective rate: {effective_rate:.2f}"
+    )
+
+
+# limiter = TokenBucketLimiter(10, 10)
+# make_requests(100, limiter)

rate_limiters/uv.lock

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