cqrs

How do you ensure consistent client reads in an eventual consistent system?

由 不打扰是莪最后的温柔 提交于 2019-12-03 10:16:28
问题 I'm digging into CQRS and I am looking for articles on how to solve client reads in an eventual consistent system. Consider for example a web shop where users can add items to their cart. How can you ensure that the client displays items in the cart if the actual processing of the command "AddItemToCart" is done async? I understand the principles of dispatching commands async and updating the read model async based on domain events, but I fail to see how this is handled from the clients

Reporting in the CQRS/ES world

由 匿名 (未验证) 提交于 2019-12-03 10:10:24
可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I think I understand the idea of the read model in the context of ES + CQRS (please correct me if not). However, I still have a few doubts about using it in the context of ‘serious’ reporting. Let us say I use a relational db plus some ORM to crud my read models. One basic ‘summary stats read model’ could look like this: class SummaryStats1 { public Guid TypeId { get; set; } public string TypeName { get; set; } public Guid SubTypeId { get; set; } public string SubTypeName { get; set; } public int Count { get; set; } } Given an event: TypeId

CQRS - how to handle new report tables (or: how to import ALL history from the event store)

由 北慕城南 提交于 2019-12-03 08:20:04
问题 I've studied some CQRS sample implementations (Java / .Net) which use event sourcing as the event store and a simple (No)SQL stores as the 'report store'. Looks all good, but I seem to be missing something in all sample implementations. How to handle the addition of new report stores / screens, after an application has gone in production? and how to import existing (latest) data from the event store to the new report store? Ie: Imagine a basic DDD/CQRS driven CRM application. Every screen

Akka.Net VS MS Orleans Comparison [closed]

由 半世苍凉 提交于 2019-12-03 08:08:07
问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 3 years ago . I've started implementing several LOB application with CQRS/ES and for this evaluating: several EMS: NServiceBus, MassTransit, RhinoMessageBus Akka.net + DDDD MS Orleans + DDDD There are lot of comparisons of different EMSs but no evaluations of Actor Frameworks. So, could you

CQRS (event sourcing): Projections with multiple aggregates

由 家住魔仙堡 提交于 2019-12-03 08:06:06
I have a question regarding projections involving multiple aggregates on a CQRS architecture. For example sake, suppose I have two aggregates WorkItem and Developer and that the following events happen sequentially (but not immediately) WorkItemCreated (workItemId) WorkItemTitleChanged (workItemId, title) DeveloperCreated (developerId) DeveloperNameChanged (developerId, name) WorkItemAssigned (workitemId, DeveloperId) I wish to create a projection which is as "inner join" of developer-workitem: | WorkItemId | DeveloperId | Title | DeveloperName | ... | |------------|-------------|--------|----

Relational database schema for event sourcing

由 自作多情 提交于 2019-12-03 07:31:27
I am trying to store domain events in a postgres database. I am not sure in many things, and I don't want to redesign this structure later, so I am seeking for guidance from people who have experience with event sourcing. I have currently the following table: domain events version - or event id, integer sequence, helps to maintain order by replays type - event type, probably classname with namespace aggregate - aggregate id, probably random string for each aggregate timestamp - when the event occured promoter - the promoter of the event, probably user id details - json encoded data about the

Command Validation in DDD with CQRS

由 人走茶凉 提交于 2019-12-03 07:20:38
问题 I am learning DDD and making use of the CQRS pattern. I don't understand how to validate business rules in a command handler without reading from the data store. For example, Chris wants to give Ashley a gift. The command might be GiveGiftCommand. At what point would I verify Chris actually owns the gift he wants to give? And how would I do that without reading from the database? 回答1: There are different views and opinions about validation in command handlers. Command can be rejected , we can

User Auth in EventSourcing applications

由 徘徊边缘 提交于 2019-12-03 07:14:15
问题 I'm looking into crafting an app with DDD+CQRS+EventSourcing, and I have some trouble figuring out how to do user auth. Users are intrinsically part of my domain, as they are responsible for clients. I'm using ASP.NET MVC 4, and I was looking to just use the SimpleMembership. Since logging in and authorising users is a synchronous operation, how is this tackled in an eventually consistent architecture? Will I have to roll my own auth system where I keep denormalized auth tables on the read

Handling duplication of domain logic using DDD and CQRS

由 血红的双手。 提交于 2019-12-03 06:57:39
问题 I'm experimenting with DDD + CQRS and I can not understand how to handle this domain logic duplication problems: First, about duplication across domains: Scenario 1: Let's say I have some application which handles office employees. I have 3 bounded contexts: Programmer department, QA department and Audit Department. Each BC has it's own AR: "Programmer", "Tester", "Worker". They are 99% different, with different logic in each, however, each of those have "Name", "Surname" and a simple method

Add validation to a MediatR behavior pipeline?

由 假如想象 提交于 2019-12-03 06:57:14
问题 I'm using ASP.NET Core, the built-in container, and MediatR 3 which supports "behavior" pipelines: public class MyRequest : IRequest<string> { // ... } public class MyRequestHandler : IRequestHandler<MyRequest, string> { public string Handle(MyRequest message) { return "Hello!"; } } public class MyPipeline<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse> { public async Task<TResponse> Handle(TRequest request, RequestHandlerDelegate<TResponse> next) { var response = await next();
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