How do you test your domain when Event Sourcing? I find testing aggregates with Event Sourcing to be simpler than testing if you’re storing the current state. The inputs to your aggregate are events and the output of your aggregate are events.
The term “Event” is really overloaded. There are many different utilities that leverage events. Event Sourcing, Event Carried State Transfer, and Event Notifications. None of these are for the same purpose. When talking about an Event Based architecture, realize which one you’re using and for what purpose.
DDD是近年软件设计的热门。CQRS与Event Sourcing作为实施DDD的一种选择，也逐步进入人们的视野。围绕这两个主题，软件开发的大咖[Martin Fowler]、[Greg Young]、[Udi Dahan]分别有所论述，[MSDNC QRS Journey]、[Implementing DDD]、[Patterns, Principles, and Practices of DDD]等著述也提供了范例，国内外各大论坛的文章和DDD开源框架更是数不胜数，为学习CQRS和Event Sourcing提供了大量指导。其中，Greg Young的论文最为系统。故本文通过解读其论文，简单梳理了CQRS与Event Sourcing的发展脉络，厘出其中的主要技术重点，并提出以Akka作为落地方案，以求对这两个主题有一个较为全面的总结。错谬之处，还望指正。
In previous posts in this series, I covered what a Modular Monolith is, what its architecture looks like and how this architecture can be enforced. Then I described architectural drivers for this architecture and styles of integration between modules. In this post I would like to go deeper – a level lower and describe how such architecture can be designed. We are not going to implement this architecture yet – we will focus on its technology-agnostic design.
Although Command Query Responsibility Segregation (CQRS) seems to be a term a lot of developers are aware of, I do think the majority have the wrong definition. Like many terms in the software development industry, things over time get confused, and then those confusing ideas propagate. These are the 3 CQRS Myths I see or hear the most often.
Domain events are one of my favorite patterns and one Julie Lerman and I cover in our DDD Fundamentals course, on Pluralsight. I differentiate between two kinds of domain events: pre-persistence and post-persistence. You'll find a good implementation of post-persistence domain events (using MediatR) in my Clean Architecture solution template. However, until recently, I hadn't built an immediate, pre-persistence implementation of domain events for .NET using MediatR. This is meant to follow a similar approach to Udi Dahan's classic static helper, which relied on StructureMap and static methods.
ElasticSearch是一个用Java语言开发的分布式文档检索引擎。也支持文档存储功能,且不会将信息类似SQL存储为列数据,而是存储已序列化的JSON文档的复杂数据结构。而且ElasticSearch支持集群部署,当集群中有多个ElasticSearch节点时,存储的文档会分布在整个集群中,并且可以从任何节点立即访问。ElasticSearch是基于 Lucene 的搜索服务器,并且提供了标准的 RESTful web接口,作为 Apache 许可条款下的开放源码发布。
The purpose of this article is to present a fast and lightweight implementation of the CQRS+ES pattern using the C# programming language and the .NET Framework. This implementation is relatively full-featured, including support for SQL Server serialization of commands and events, scheduled commands, snapshots, sagas (i.e., process managers), and plug-and-play overrides for multitenant customization. I will describe how the code is structured, and illustrate how it works with a sample application.
This article is about my experiences of applying a Domain-Driven Design (DDD) approach when working with Entity Framework Core (EF Core). I have now used DDD and my supporting libraries for two years on my own projects and client projects. Here are the bigger client projects where I used an DDD approach...
How to create better code using Domain-Driven DesignHomepage>Blog>How to create better code using Domain-Driven Design 16/03/2020Business requirements The anemic enterprise cake Project structure Where is the business logic? Issues with the anemic domain model Anemic model Primitive obsession Reada...
CQRS is a simple pattern that strictly segregates the responsibility of handling command input into an autonomous system from the responsibility of handling side-effect-free query/read access on the same system. If you are familiar with Domain-Driven Design, you’ve most likely heard about, Command-Query Responsibility Segregation (CQRS). Though the CQRS pattern is well-known, there are still a lot of misconceptions around this pattern, especially when it comes to applying it in real-world software projects. In this article, you will learn exactly what CQRS is, the principles behind it, and the benefits it can provide for your project.
Building microservices through Event Driven Architecture part11: Run Unit tests inside a docker container
This tutorial is the 11th part of a series : Building microservices through Event Driven Architecture. The previous step is about building microservices through Event Driven Architecture part10: Handling updates : https://logcorner.com/building-microservices-through-event-driven-architecture-part10-handling-updates-and-deletes/. In this tutorial, I will show how to run unit tests inside a docker container.
This question posted on Twitter (and the subsequent thread) caught my attention. I had to pipe in with my own opinion on having queries without repositories. To summarize, the question is about using Aggregate Roots with an ORM like Entity Framework. Should you eager load all navigation properties or alternatively I guess, use lazy loading? My answer is if you’re only using an aggregate root for commands (to change state) and you generally have a higher read to write ratio, then eager load the navigation properties. As a general rule of thumb.
I never bought into the ‘agile will save us all’ philosophy that permeates the True Believers. It’s not because I don’t believe them — I do. Operating according to the agile manifesto is a step up. It’s a big step up. Scrum provides a framework for operating with agility, and I’ve been a part of organizations that were successful and had adopted Scrum.
In this blog entry I give a primer on Clean Architecture, which is a modern, scalable formal software architecture which is appropriate for modern web applications. Next, I discuss how Domain-Driven Design fits into this picture, and how DDD concepts dovetail nicely into Clean Architecture, producing a methodology called Clean DDD. Finally, I introduce Command Query Responsibility Segregation (CQRS), and describe how it complements and enhances Clean DDD solutions to create software systems that are elegant, robust, scalable, and testable.