Transaction log tailling
Context
You have applied the [[Transactional Outbox]] pattern.
Forces
Solution
Tail the database transaction log and publish each message/event inserted into the outbox to the message broker.
The mechanism for trailing the transaction log depends on the database:
MySQL binlog
Postgres WAL
AWS DynamoDB table streams
Example
Eventuate Tram framework implements transaction log tailing.
Resulting context
This pattern has the following benefits:
No 2PC
Guaranteed to be accurate
This pattern has the following drawbacks:
Relatively obscure although becoming increasing common
Requires database specific solutions
Tricky to avoid duplicate publishing
Related patterns
The [[Transactional Outbox]] pattern creates the need for this pattern
The [[Polling publisher]] pattern is an alternative solution
Learn more
My book Microservices patterns describes this pattern in a lot more detail.
The Eventuate Tram framework implements this pattern
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