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