Contents
What is transactional outbox pattern?
Transactional Outbox is a pattern to reliably publish messages without the use of distributed transactions. It has two parts , the Outbox and the message dispatcher which work togethar to reliably persist state and publish messages.
Why outbox pattern?
The Outbox pattern provides an easy and flexible approach to provide messages for other microservices without requiring distributed transactions. In the next step, you need to implement another service, which gets the messages from the outbox table and sends them to a message broker, e.g. a Kafka instance.
Does outbox mean it’s been sent?
The outbox is a holding cell for your messages until they are sent to the recipient successfully by the server. The sent folder is the collection of all the messages that have been successfully delivered to the recipient by the mail server.
How does the transactional outbox pattern work in SQL?
The Transactional outbox pattern uses the primary persistance layer (database, either a SQL or NOSQl) as a temporary message queue. The service that sends messages has an OUTBOX database table. As part of the database transaction that creates, updates, and deletes entities, the service sends messages by inserting them into the OUTBOX table.
How is atomicity guaranteed in an outbox transaction?
The service that sends messages has an OUTBOX database table. As part of the database transaction that creates, updates, and deletes entities, the service sends messages by inserting them into the OUTBOX table. Atomicity is guaranteed because this is a local ACID transaction.
Is the outbox pattern based on guaranteed delivery pattern?
The Outbox Pattern is based on Guaranteed Delivery pattern and looks as follows: When you save data as part of one transaction, you also save messages that you later want to process as part of the same transaction. The list of messages to be processed is called an Outbox, just like in e-mail clients.
How is the messagerelay used in the outbox?
The MessageRelay publishes messages from the outbox to the message broker, sending one to its destination message channel. It deletes those messages from the OUTBOX table. The MessageRelay can be built either as a polling publisher or using the transaction log tailing pattern