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How to Limit Concurrent Requests with a Semaphore in Python
Use threading.Semaphore with a ThreadPoolExecutor to cap how many worker threads run simultaneously, preventing resource overload.
import threading
import time
from concurrent.futures import ThreadPoolExecutor
def worker(name, semaphore, results):
with semaphore:
results.append(f"start {name}")
time.sleep(0.5) # simulate async work
results.append(f"done {name}")
def main():
sem = threading.Semaphore(2) # max 2 …Simulate a Leaky Bucket Rate Limiter in Python
This code implements a leaky bucket rate limiter that drains at a fixed rate and accepts or rejects incoming requests based on capacity.
import time
from collections import deque
class LeakyBucket:
"""Simulates a leaky bucket rate limiter with a fixed drain rate."""
def __init__(self, capacity, drain_rate_per_sec):
self.capacity = capacity
self.drain_rate = drain_rate_per_sec
self.water = 0.0
self.last_refill =…Build a Bulk Array POST Mock Server in Python
Creates an HTTP mock server that accepts POST requests with a JSON array and returns incremental IDs for each item.
import json
from http.server import BaseHTTPRequestHandler, HTTPServer
from urllib.parse import urlparse
class MockHandler(BaseHTTPRequestHandler):
def do_POST(self):
if urlparse(self.path).path != "/bulk":
self.send_response(404)
self.end_headers()
return
cont…How to Build an Idempotency-Key POST Handler in Python
Python HTTP server mock that accepts POST requests and deduplicates them using an Idempotency-Key header, returning the same response for repeated calls.
import hashlib
import json
from http.server import BaseHTTPRequestHandler, HTTPServer
from urllib.parse import urlparse
class MockAPI(BaseHTTPRequestHandler):
responses = {}
def do_POST(self):
length = int(self.headers.get("Content-Length", 0))
body = self.rfile.read(length).decode("utf-8")
…How to Mock a Webhook Subscribe Callback URL in Python
Mock a webhook subscribe callback URL using Python's http.server to receive and parse POST requests sent by webhook providers.
import json
from http.server import BaseHTTPRequestHandler, HTTPServer
class WebhookHandler(BaseHTTPRequestHandler):
def do_POST(self):
content_length = int(self.headers.get('Content-Length', 0))
payload = json.loads(self.rfile.read(content_length)) if content_length else {}
print…Implement If-Match Precondition Update in Python
A mock resource store that uses the If-Match header's ETag to guard updates, preventing overwrites from stale clients.
from dataclasses import dataclass
from typing import Optional
@dataclass
class Resource:
id: str
version: int = 1
data: str = ""
etag: str = "etag-1"
class MockResourceStore:
def __init__(self):
self.resources = {}
def update(self, resource_id: str, new_data: str, if_match: Optiona…How to Implement Hedged Requests in Python
This code demonstrates a hedged request pattern using threading, which sends duplicate calls and returns the first result that arrives within a timeout.
import time
from unittest.mock import Mock
def hedged_request(call, timeout=0.05):
"""Execute two duplicate calls, return first result within timeout."""
result_container = {}
def run_and_store():
result_container['result'] = call()
result_container['done'] = True
# Simulate slow cal…How to Implement a Token Bucket Rate Limiter per Client IP in Python
Implements a simple sliding-window rate limiter using a dictionary of timestamp lists per client IP to limit requests per window.
from time import time
from collections import defaultdict
class RateLimiter:
def __init__(self, max_requests: int, window_seconds: int):
self.max_requests = max_requests
self.window_seconds = window_seconds
self.clients = defaultdict(list)
def allow(self, ip: str) -> bool:
now…How to implement rate limiting per API key in Python
A simple sliding-window rate limiter that tracks request timestamps per API key and rejects requests exceeding the configured limit.
import time
API_RATE_LIMITS = {"api_key_1": 5, "api_key_2": 3} # max requests per window
WINDOW_SECONDS = 10
class RateLimiter:
def __init__(self, limits, window):
self.limits = limits
self.window = window
self.requests = {key: [] for key in limits}
def allow(self, api_key):
…Token bucket rate limiter in Python (in-memory)
Implement a thread-safe in-memory token bucket rate limiter that throttles requests based on a steady refill rate.
import time
import threading
class TokenBucket:
def __init__(self, capacity, refill_rate, refill_interval=1.0):
self.capacity = capacity
self.tokens = capacity
self.refill_rate = refill_rate
self.refill_interval = refill_interval
self.last_refill = time.monotonic()
…How to Create and Verify HMAC SHA256 API Signatures in Python
Generate and verify HMAC-SHA256 signatures for API requests using Python's hmac, hashlib, and base64 modules.
import hmac
import hashlib
import base64
import json
from datetime import datetime, timezone
def create_api_signature(secret_key: str, method: str, path: str, timestamp: str, body: dict = None) -> str:
"""Create HMAC-SHA256 signature for API request."""
payload = {
"method": method.upper(),
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