Python CQRS Framework - vadikko2

Python event-driven framework supporting CQRS, Event Sourcing, Orchestrated Saga, and Transactional Outbox for reliable event delivery with Kafka integration.

Summary

This framework provides a full-stack implementation of CQRS, Event Sourcing, Orchestrated Saga, and Transactional Outbox in Python, with Kafka as the event transport. The combination addresses a common production requirement: a Python microservice that participates in distributed transactions while guaranteeing reliable event delivery even under partial failures.

The Orchestrated Saga implementation handles distributed transaction management via compensation transactions. When a saga step fails, the framework executes compensating actions for all previously completed steps in reverse order, restoring system consistency without requiring a distributed transaction coordinator. This enables complex multi-service workflows to maintain data consistency in the face of partial failures.

The Transactional Outbox pattern ensures reliable event publishing: events are written to an outbox table in the same local transaction as the business state change, then a separate relay process reads the outbox and publishes to Kafka. This guarantees that events are published if and only if the state change commits, eliminating the dual-write problem. The circuit breaker integration wraps outgoing command dispatch to prevent cascade failures when downstream services are unavailable.

Key Arguments

• Explicit command/query separation in Python benefits from framework enforcement of the distinction
• Orchestrated Saga with compensation transactions handles distributed transaction rollback across services
• Transactional Outbox ensures events are reliably published even when the message broker is temporarily unavailable
• Kafka integration enables scalable event streaming for high-volume command and event workloads
• Circuit breaker wrapping of outgoing commands prevents cascade failures when downstream services fail

Concepts Covered

• CQRS — Python implementation with command bus and query bus
• Event Sourcing — aggregate persistence via events in Python
• Saga Pattern — orchestrated compensation transaction implementation
• Outbox Pattern — reliable event delivery guaranteeing at-least-once publishing
• Apache Kafka — event transport for command and event streams
• Circuit Breaker Pattern — cascade failure prevention for outgoing commands

Quality Notes

Useful for Python practitioners implementing the full CQRS+ES+Saga+Outbox stack. Demonstrates how the patterns combine in a single framework, which is rare in Python-specific resources. The Outbox and Saga implementations are the most distinctive contributions.