# 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](https://github.com/eventuate-tram/eventuate-tram-core) 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](https://microservices.io/book) describes this pattern in a lot more detail.
* The [Eventuate Tram framework](https://github.com/eventuate-tram/eventuate-tram-core) implements this pattern