Polling publisher

Context

You have applied the [[Transactional Outbox]] pattern.

Problem

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

Forces

Solution

Publish messages by polling the database's outbox table.

Examples

Eventuate Tram framework implements polling.

Resulting context

This pattern has the following benefits:

• Works with any SQL database

This pattern has the following drawbacks:

• Tricky to publish events in order

• Not all NoSQL databases support this pattern

Related patterns

• The [[Transactional Outbox]] pattern creates the need for this pattern.

• The [[Transaction log tailing]] 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