Problem
How to publish messages/events into the outbox in the database to the message broker?
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
