Reference library

Streaming & messaging

Kafka-style pub/sub, event consumers, async pipelines, and message-driven workflows.

4 matches

How to Build a Flow Control Credit Window in Python

A Python class that reserves, confirms, releases, and settles credit to limit message flow and prevent overload in streaming pipelines.

flow-control credit-window streaming

Python

class CreditWindow:
    def __init__(self, max_credit=1000):
        self.max_credit = max_credit
        self.used_credit = 0
        self.pending_credit = 0
    
    def try_reserve(self, amount):
        available = self.max_credit - self.used_credit - self.pending_credit
        if available >= amount:
           …

14 0 Open

Streaming & messaging medium

How to Mock NATS Subject Hierarchies with Wildcards in Python

Build a lightweight NATS-style pub/sub mock that matches subject hierarchies with '*' and '>' wildcards for tests or prototypes.

nats pubsub wildcards

Python

# Mock a simplified NATS subject hierarchy with wildcard matching
# Supports: exact match, '*' (single token), '>' (tail wildcard)

class NATSSubjectMock:
    def __init__(self):
        self.subscriptions = {}  # subject -> list of callbacks

    def subscribe(self, subject, callback):
        self.subscriptions.setd…

13 0 Open

Streaming & messaging medium

How to mock a CQRS projector read model update in Python

Build a CQRS projector class that maintains denormalized read models by applying domain events in a mock order-processing service.

cqrs projector read-model

Python

from dataclasses import dataclass, field
from typing import Dict, List, Optional


@dataclass
class OrderReadModel:
    order_id: str
    customer_name: str
    total: float
    status: str = "pending"
    items: List[Dict] = field(default_factory=list)

    def apply_event(self, event_type: str, payload: Dict) -> Non…

11 0 Open

Streaming & messaging medium

In-Memory PubSub Topic Subscribe Mock in Python

Build a thread-safe in-memory publish/subscribe mock where handlers subscribe to named topics and receive every message published to them.

pubsub mock events

Python

class PubSub:
    def __init__(self):
        self.topics = {}

    def subscribe(self, topic, callback):
        if topic not in self.topics:
            self.topics[topic] = []
        self.topics[topic].append(callback)

    def publish(self, topic, message):
        for callback in self.topics.get(topic, []):
    …

16 0 Open

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