Streaming & messaging
Kafka-style pub/sub, event consumers, async pipelines, and message-driven workflows.
Batch Consume Process Commit Pattern in Python
A mock batch processor that accumulates items in a queue, processes full batches, commits successful or failed results, and flushes remaining items.
import random
import threading
import time
from collections import deque
class MockBatchProcessor:
def __init__(self, process_func, commit_func, batch_size=5):
self.queue = deque()
self.batch_size = batch_size
self.process_func = process_func
self.commit_func = commit_func
de…Build a Streaming Messaging Helper in Python
Create a simple message stream class that stores recent messages, sends user messages, and retrieves history or latest messages with timestamps.
from collections import deque
from dataclasses import dataclass
from datetime import datetime
import time
@dataclass
class Message:
user: str
text: str
timestamp: str = ""
def __post_init__(self):
if not self.timestamp:
self.timestamp = datetime.now().strftime("%H:%M:%S")
class…Dead Letter Queue Failed Messages List Mock in Python
Implements a simple in-memory dead letter queue to collect, list, and retry failed messages, with JSON serialization for inspection in streaming pipelines.
import json
from collections import deque
class Message:
def __init__(self, message_id, payload, attempts=0):
self.message_id = message_id
self.payload = payload
self.attempts = attempts
def __repr__(self):
return f"Message(id={self.message_id}, attempts={self.attempts})"
c…How to Build a Materialized View Updater Consumer Mock in Python
A mock consumer that queues change events and triggers refresh callbacks to simulate materialized view updates.
import time
from collections import deque
from dataclasses import dataclass, field
from typing import Callable, Deque, Optional
@dataclass
class MaterializedViewUpdater:
"""Mock updater that consumes change events and refreshes a view."""
refresh: Optional[Callable[[str], None]] = None
queue: Deque[tuple…How to Build a Message Stream Queue in Python
A beginner-friendly MessageStream class built on deque that sends messages one at a time, tracks unread counts, and records sent items.
from collections import deque
import time
class MessageStream:
def __init__(self, messages):
self._queue = deque(messages)
self._sent = []
def send_next(self):
if not self._queue:
return None
message = self._queue.popleft()
self._sent.append(message)
…How to Implement At-Least-Once Delivery with Acknowledgment in Python
This code demonstrates a mock message broker with at-least-once delivery, including retry logic and acknowledgment after successful processing.
import time
import uuid
from collections import deque
class MockMessageBroker:
def __init__(self):
self.queue = deque()
self.acked = set()
def publish(self, payload: str) -> str:
msg_id = str(uuid.uuid4())
self.queue.append((msg_id, payload))
return msg_id
def po…How to Implement Backpressure Pause Producer with a Bounded Queue in Python
Places a Producer thread that sends items into a bounded queue with backpressure: on Full, it pauses to let the consumer catch up.
import threading
import time
import queue
import random
class Producer:
def __init__(self, q):
self.q = q
self.running = True
def produce(self):
while self.running:
item = random.randint(1, 100)
try:
self.q.put(item, timeout=0.5)
…How to Implement a Priority Queue for Messages in Python
Build a message priority queue with heapq and dataclasses that pops messages by priority, using sequence numbers to keep insertion order.
import heapq
from dataclasses import dataclass, field
from typing import Any
@dataclass(order=True)
class Message:
priority: int
sequence: int = field(compare=False)
content: str = field(compare=False)
class PriorityQueue:
def __init__(self):
self._heap = []
def push(self, priority: int,…How to Mock RabbitMQ Ack Nack Requeue in Python
A mock RabbitMQ channel and consumer that simulates ack, nack, and requeue handling for testing message processing logic without a broker.
import json
from collections import deque
class MockChannel:
def __init__(self):
self.acked = []
self.nacked = []
self.requeued = []
def basic_ack(self, delivery_tag):
self.acked.append(delivery_tag)
def basic_nack(self, delivery_tag, requeue=False):
self.nacked.…How to Simulate RabbitMQ Exchange Routing in Python
Simulate RabbitMQ exchange routing using a nested dict, matching routing keys against patterns like error.* and info.# to return bound queues.
from collections import defaultdict
def route_message(exchanges, exchange_name, routing_key):
"""
Simulate RabbitMQ exchange routing using a nested dict structure.
Returns list of queue names that match the routing key.
"""
queues = exchanges.get(exchange_name, {})
matched = []
for pa…How to mock RabbitMQ queue binding with routing keys in Python
A mock demonstration of binding a queue to an exchange with multiple routing keys in RabbitMQ using Python and pika, without a real broker connection.
import pika
import sys
def bind_queue_with_routing(channel, queue_name, exchange_name, routing_keys):
"""
Mock RabbitMQ queue binding with routing keys.
Prints the binding configuration instead of connecting to a real broker.
"""
for routing_key in routing_keys:
binding = {
"q…Implement a FIFO Message Queue in Python with deque
This code implements a FIFO (first-in-first-out) message queue class using Python's collections.deque, providing enqueue, dequeue, peek, and size operations.
from collections import deque
class MessageQueue:
def __init__(self):
self.queue = deque()
def enqueue(self, message):
self.queue.append(message)
print(f"Enqueued: {message}")
def dequeue(self):
if self.is_empty():
print("Queue is empty, cannot dequeue.")
…Implement a retry queue with visibility timeout in Python
This code simulates a message queue with a visibility timeout, allowing messages to be retried if not deleted before the timeout expires.
import time
from collections import deque
class SimpleQueue:
def __init__(self, visibility_timeout=2):
self.queue = deque()
self.in_flight = {}
self.visibility_timeout = visibility_timeout
def send(self, message):
self.queue.append(message)
def receive(self):
if …Mock NATS queue group load balancing in Python
Simulates a NATS queue group where each message is delivered to exactly one subscriber using random selection with a lightweight mock.
import random
import time
from collections import defaultdict
class MockQueueGroup:
"""Mock a NATS queue group: each message is delivered to exactly one subscriber."""
def __init__(self, subscribers):
self.subscribers = subscribers
def publish(self, message):
receiver = random.choice(se…Simulate RabbitMQ QoS Prefetch Count in Python
Mocks RabbitMQ QoS prefetch semantics using threading and a queue to cap concurrent unacked message processing per worker.
import threading
import time
import queue
class RabbitMQMock:
def __init__(self, prefetch_count=1):
self.prefetch_count = prefetch_count
self.channel_queue = queue.Queue()
self.currently_processing = 0
self.lock = threading.Lock()
def start_consuming(self, messages, worker_co…Browse by section
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Streaming & messaging — Python code examples
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