In this chapter, we’d like to show how the events metaphor can be extended to encompass the way that we handle incoming and outgoing messages from the system. Internally, the core of our application is now a message processor. Let’s follow through on that so it becomes a message processor externally as well.

We’ll see how our Service Layer and Unit of Work patterns allow us to reconfigure our app to run as an asynchronous message processor, and how event-driven systems help us to decouple aggregates and applications from one another.

Then we’ll show how to use the Domain Events pattern to separate side effects from our use cases, and how to use a simple Message Bus pattern for triggering behavior based on those events.

Jun 3, 2020 · Along with my coauthor Bob, we are proud to release "Architecture Patterns with Python", which you can find out more about at cosmicpython.com. The cosmic soubriquet is a little joke, Cosmos being the opposite of Chaos in ancient Greek, so we want to propose patterns to minimise chaos in your applications.

Event-Driven Architecture: Using Events to Integrate Microservices In the preceding chapter, we never actually spoke about how we would receive the "batch quantity changed" events, or indeed, how we might notify the outside world about reallocations.

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Dec 23, 2024 · Implementing Event-Driven Architecture (EDA) involves several components, including event sources, an event bus, and subscribers. Here, we will implement a simplified example using Python and a basic event handling mechanism.

Apr 17, 2025 · — Cosmic Python. Unwanted coupling is easy to accidentally introduce into your application. Most of the time, we couple things together because it seems like a good idea at the time. ... Communicating well with event modeling diagrams and an even-driven, vertically sliced architecture, you can have similar gains. The three practices together ...

Oct 1, 2024 · In this guide, we explain how to diagram event-driven architectures using the C4 model. We’ll use a practical example from the Architectural Kata 2024 winner and discuss the pros and cons...

Event-driven architecture (Chapters 8-11) We introduce three more mutually reinforcing patterns: the Domain Events, Message Bus, and Handler patterns. Domain events are a vehicle for capturing the idea that some interactions with a system are triggers for others.