lizhanhui opened a new issue #292: RocketMQ Feature Request: Transaction-Aware Message URL: https://github.com/apache/rocketmq/issues/292 Messaging is a major approach to decouple distributed systems. However, when trying to decouple system modules whose boundaries are associated with transactions, it is subtle to determine when to send messages. For example, when module A completes a database transaction, it needs to send a message to notify module B, C, and D to perform subsequent actions. The problem is what the best time point to send the message is in comparison with database transaction. If we sent the message before database transaction, what if the application or database server crashed out. The same counts if the transaction rolls back due to any potential reason. If we sent the message after the transaction commits, there will be chances that application server may suffer crashes before message delivery is made. Thus, to maintain consistency of the whole system, we need to either implement an extra module to periodically check messages of each transaction is sent given messages are designed to send after the transaction commits and supplementally send those missed ones to achieve eventual consistency or make our messaging system transaction aware. The first option is viable, but it excessively complicates business application systems and brings about noticeable overhead as the extra module has to repeatedly check committed transactions and messages sent are in accordance after a period of time. The latter choice, however, confines complexities to the messaging system itself and once achieved, all application developers may enjoy simplicity and consistency. To achieve the goal described above, we define a new type of message: transaction aware message. A transaction-aware message is composed of a pair of deliverable messages: prepare-message and commit/rollback message. Prepare messages are supposed to be sent before local transaction commits/roll-back, which are not visible to consumers. Commit/rollback messages are sent after transaction commits/rolls back. Brokers are responsible to inquire application servers, which share the same role with those prepare-message senders, to handle pending prepare messages after the defined period of time. On receiving of the commit message, the transaction aware message is made visible to consumers; Similarly, on receiving of rollback message, pending status of the corresponding prepare message is canceled quietly and consumers are completely unaware in the whole process.
---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
