Module dk.cloudcreate.essentials.components.foundation
Package dk.cloudcreate.essentials.components.foundation.messaging.eip.store_and_forward

Interface Outbox

All Known Implementing Classes:
Outboxes.DurableQueueBasedOutboxes.DurableQueueBasedOutbox
public interface Outbox
The Outbox supports the transactional Store and Forward pattern from Enterprise Integration Patterns supporting At-Least-Once delivery guarantee.
The Outbox pattern is used to handle outgoing messages, that are created as a side effect of adding/updating an entity in a database, but where the message infrastructure (such as a Queue, Kafka, EventBus, etc.) that doesn't share the same underlying transactional resource as the database.
Instead, you need to use an Outbox that can join in the same UnitOfWork/transactional-resource that the database is using.
The message is added to the Outbox in a transaction/UnitOfWork and afterwards the UnitOfWork is committed.
If the transaction fails then both the entity and the message will be rolled back when then UnitOfWork rolls back.
After the UnitOfWork has been committed, the messages will be asynchronously delivered to the message consumer in a new UnitOfWork.
The Outbox itself supports Message Redelivery in case the Message consumer experiences failures.
This means that the Message consumer, registered with the Outbox, can and will receive Messages more than once and therefore its message handling has to be idempotent.

If you're working with OrderedMessage's then the Outbox consumer must be configured with OutboxConfig.getMessageConsumptionMode() having value MessageConsumptionMode.SingleGlobalConsumer in order to be able to guarantee that OrderedMessage's are delivered in OrderedMessage.getOrder() per OrderedMessage.getKey() across as many OutboxConfig.numberOfParallelMessageConsumers as you wish to use.