Reliability & rate limiting
Retries, exponential backoff, circuit breakers, token buckets, and idempotent handlers.
Mock Distributed Rate Limiter with Dict in Python
Simulates a distributed token-bucket rate limiter with a thread-safe dict, useful for testing before moving to Redis.
import time
import threading
from collections import defaultdict
class DistributedRateLimiter:
"""
A mock distributed rate limiter using a dict with thread-safe access.
Implements a token bucket algorithm per user.
"""
def __init__(self, rate_per_second=5, burst_capacity=10):
self.rate_p…Mock a Two-Phase Commit Coordinator in Python
Simulates a two-phase commit protocol where a coordinator asks participants to prepare, then commits or aborts based on unanimous readiness.
import random
import time
from typing import Dict, List
class TwoPhaseCommitCoordinator:
def __init__(self, participants: List[str]):
self.participants = participants
self.participant_state: Dict[str, bool] = {}
def prepare(self) -> bool:
print("[Coordinator] Phase 1: Prepare")
…Rate Limit per User ID in Python with a Dict Mock
Implements a simple sliding window rate limiter using a defaultdict of timestamps per user ID, blocking requests that exceed a max count within a time window.
import time
from collections import defaultdict
class RateLimiter:
def __init__(self, max_requests, window_seconds):
self.max_requests = max_requests
self.window_seconds = window_seconds
self.user_timestamps = defaultdict(list)
def allow_request(self, user_id):
now = time.tim…Rate Limiting in Python with a Sliding Window
A beginner-friendly dataclass-based sliding window rate limiter that controls how many calls are allowed per time window.
import time
from dataclasses import dataclass
@dataclass
class RateLimiter:
max_calls: int
window_seconds: float = 1.0
def __post_init__(self):
self.calls = []
self._start = time.monotonic()
def _update(self, now):
self.calls = [t for t in self.calls if now - t < self.window…Rate Limiting with Queue Rejection in Python
Simulates a load shed pattern that rejects tasks when a queue fills up.
from collections import deque
import time
class RateLimiter:
def __init__(self, max_queue_size=3):
self.queue = deque()
self.max_queue_size = max_queue_size
self.rejected_count = 0
def submit(self, task_name):
if len(self.queue) >= self.max_queue_size:
self.reject…Rate Limiting with a Simple Python RateLimiter Class
A beginner-friendly Python rate limiter that tracks call timestamps and enforces a maximum number of calls within a rolling time window, with a helper to validate positive integers.
import time
class RateLimiter:
def __init__(self, max_calls, period_seconds):
self.max_calls = max_calls
self.period_seconds = period_seconds
self.calls = []
def is_allowed(self):
now = time.time()
while self.calls and now - self.calls[0] >= self.period_seconds:
…Retry with Exponential Backoff and Jitter in Python
A decorator-style retry wrapper that retries a flaky function with exponential backoff plus random jitter, then raises after the last attempt fails.
import random
import time
def retry_with_backoff(func, max_retries=3, base_delay=0.5, max_jitter=0.1):
for attempt in range(max_retries + 1):
try:
return func()
except Exception as e:
if attempt == max_retries:
raise
delay = base_delay * (2 ** at…Saga Compensating Transaction Mock in Python
Simulates a distributed transaction using a saga pattern with compensating actions that roll back steps on failure.
import random
import time
class OrderService:
def __init__(self):
self.orders = {}
def create_order(self, order_id):
print(f"[Order] Creating order {order_id}...")
time.sleep(0.1)
if random.random() < 0.3: # 30% chance of failure
raise RuntimeError(f"Order {order…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()
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Reliability & rate limiting — Python code examples
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