Hi
I have some doubt regarding Kafka integration how the publisher notify if one consumer fail? and how the unitofwork works
ex.
**Publisher: **
I want to keep copy of country to all microservice.
Consumer
if consumer fail I want to rollback the transaction in publisher?
Is this possible using the build in distributed events using kafka?
Thanks
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10 Answer(s)
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Hi,
You can see the document: https://docs.abp.io/en/abp/latest/Distributed-Event-Bus#transaction-and-exception-handling
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I follow and implement the Kafka integration base on document you've send but still rollback is not working. even I manually throw exception to consumer.
still the behavior is the same once consumer fail my transaction in publisher success.
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When you switch to an actual distributed event bus provider (e.g. Kafka or RabbitMQ), then the event handlers will be executed in different processes/applications as their purpose is to create distributed systems. In this case, the only way to implement transactional event publishing is to use the outbox/inbox patterns as explained in the Outbox / Inbox for Transactional Events section.
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Publisher configuration
Consumer configuration
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but still rollback is not working. even I manually throw exception to consumer.
When you successfully publish an event, it's not possible to rollback. you might consider posting a rollback event to rollback your changes
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it seems this became more complicated and hard to maintain because what if there is cascading events with insert and update.
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but still rollback is not working. even I manually throw exception to consumer.
When you successfully publish an event, it's not possible to rollback. you might consider posting a rollback event to rollback your changes
then how you will notify the UI Realtime if the consumer is fail during rollback event.
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As you know, Kafka is a distributed message system, and messages can be consumed in parallel. Even if one message fails it will not affect the other.
You should not throw unhandled exceptions in the event handler, it keeps retrying in the system and blocks your other event handlers(In the outbox/inbox patterns, messages are sequential)
Your event handlers should be independent of each other, if one fails, you need to roll back all published events, you should place the code logic before publishing the event instead of an event handler
then how you will notify the UI Realtime if the consumer is fail during rollback event.
Same, Kafka is a distributed application, it can't show notify the UI in real-time, but you can build a real-time notification system(SignalR)
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thanks I will consider that.
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ok
