[Features] Introducing a new EventBus CAP for eshop #970
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… requires MongoDB version to be larger than 4.0 and enable clustering to use the local storage transaction provided by MongoDB
… requires MongoDB version to be larger than 4.0 and enable clustering to use the local storage transaction provided by MongoDB
… requires MongoDB version to be larger than 4.0 and enable clustering to use the local storage transaction provided by MongoDB
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It is pleasure to hear that CAP has been integrated into the sample project eShopOnContainers. 😁 |
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Hi @yang-xiaodong, Thanks for dedicating so much effort to get into the eShopOnContainers' internals. There are several issues with this PR that deserve some special comments.
Anyway, this just my (biased) opinion and the final decision is, of course, on @CESARDELATORRE . Cheers. cc/ @nishanil |
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Hello @mvelosop ,
Yes , this is really a very large PR, and I understand that the large PR is difficult to accept for the open source projects, but I think it is worth it.
Yes, I removed the EventBus building blocks and replaced it with the abstraction provided by CAP. It is roughly divided into two steps :
When the CAP startup, it generates the inbox table and the outbox table to the microservices database to ensure atomicity with the local transaction operations, and the CAP will take over the transaction object of the database context in the business operation to guarantee and store the atomicity of the event operation. You can see here how to implement atomic operations between business code and storage events at here. Of course, the integration events are only published if the domain events chain transaction completes successfully. Their implementation is slightly different for different databases. For example, in SQL Server, we use the Diagnostics feature provided by the SQL Client to detect the commit operation of the transaction and the code is here.
Inside the CAP, there is a wrapper around the integration event transport object. We can track the event associations in the database based on the internal number, and CAP provides a Dashboard UI for user to search.
Yes, CAP hides some details about the implementation of EventBus, and provide different message queues and different event storage extension packages. In this PR, there are some integration events that are used the in-memory storage extension package., because these microservices use databases such as Redis that do not support ACID, obviously they can't guarantee atomicity. MongoDB supports ACID transaction operations since version 4.0+, and CAP has provided support for it, but the MongoDB currently used by eshop is not a cluster, so it can not used and I use in-memory storage instead. |
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@yang-xiaodong @mvelosop
CAP worked outstanding ! |
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Adding @eiximenis and @unaizorrilla so they can also evaluate and provide feedback. I think it might not make sense to put CAP under our EventBus abstractions since CAP already has its opinionated interfaces offering further features and also works on top of Azure Service Bus, RabbitMQ and Kafka. It wouldn't make sense to have two layers of abstractions, right? However, eShopOnContainers aims to provide patterns implementation for learning purposes. Being prescriptive with CAP or any other Service Bus is a different thing.. Why CAP and not NServiceBus, MassTranssit or any other Service Bus approach? @yang-xiaodong - What you could do is to fork eShopOnContainers and have that implementation in a different repo, such as the NServiceBus eShopOnContainers implementation here: https://github.com/Particular/eShopOnContainers So we could also point to your CAP implementation from the documentation and the GitHub repo. Thoughts? |
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@CESARDELATORRE Thanks for your reply, I agree with you about that current patterns implementation for learning purpose. I will fork the eShopOnContainers and provide EventBus integration with CAP. In fact, it is the repository pointed to by the current PR and I have changed the default branch to CAP. Should I submit a PR that modifies README to point to my repository? Can accept？ |
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Hello @CESARDELATORRE, I have submitted a PR (#975) about adding EventBus note to the README. I will complete the description in my eShopOnContainers branch later. Thanks ! :) |
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Hi @yang-xiaodong, I'm closing this PR now, just waiting for your update to PR #975 |
Hello :
I am the creator of CAP, and also a Microsoft MVP who loves open source very much. I saw eShop's EventBus a few months ago. It looks a bit simplistic and I found a lot of EventBus related in the issue list, and I answered some of them.
Last year, I opened an issue(#753) to ask if there was a plan to use a third-party event integration library, but I was frustrated that I didn't get more responses.
Recently, I had more time to do the extra works. I spent some time completing the CAP integration work for eshop and had already done the tests. He worked very well and saved a lot of code.
Here are the main changes I made:
Let me know if PR needs to be merged into a new feature branch.
I will reopen the issue(#753) so that we can discuss.
Looking forward to your feedback.
@mvelosop @CESARDELATORRE @eiximenis