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.

Method Summary

Modifier and Type	Method	Description
Outbox	consume(Consumer<Message> messageConsumer)	Start consuming messages from the Outbox using the provided message consumer. This is the same as calling setMessageConsumer(Consumer) followed by startConsuming() Only needs to be called if the instance was created without a message consumer such as via Outboxes.getOrCreateOutbox(OutboxConfig)
long	getNumberOfOutgoingMessages()	Get the number of message in the outbox that haven't been sent yet
boolean	hasAMessageConsumer()	Has the instance been created with a Message consumer or has consume(Consumer) been called
boolean	isConsumingMessages()	Is the provided Message consumer consuming messages from the Outbox
OutboxName	name()	The name of the outbox
Outbox	sendMessage(Message message)	Send a message asynchronously. This message will be stored durably (without any duplication check) in connection with the currently active UnitOfWork (or a new UnitOfWork will be created in case no there isn't an active UnitOfWork). The message will be delivered asynchronously to the message consumer
default Outbox	sendMessage(Object payload)	Send a message (without meta-data) asynchronously. This message will be stored durably (without any duplication check) in connection with the currently active UnitOfWork (or a new UnitOfWork will be created in case no there isn't an active UnitOfWork). The message will be delivered asynchronously to the message consumer
default Outbox	sendMessage(Object payload, MessageMetaData metaData)	Send a message (with meta-data) asynchronously. This message will be stored durably (without any duplication check) in connection with the currently active UnitOfWork (or a new UnitOfWork will be created in case no there isn't an active UnitOfWork). The message will be delivered asynchronously to the message consumer
Outbox	setMessageConsumer(Consumer<Message> messageConsumer)	Set the message consumer.
Outbox	startConsuming()	Start consuming messages from the Outbox.
Outbox	stopConsuming()	Stop consuming messages from the Outbox.

Method Detail

consume

Outbox consume(Consumer<Message> messageConsumer)

Start consuming messages from the Outbox using the provided message consumer.
This is the same as calling setMessageConsumer(Consumer) followed by startConsuming()
Only needs to be called if the instance was created without a message consumer such as via Outboxes.getOrCreateOutbox(OutboxConfig)

If an OrderedMessage is delivered via an Outbox using a FencedLock (such as the Outboxes.durableQueueBasedOutboxes(DurableQueues, FencedLockManager)) to coordinate message consumption, then you can find the FencedLock.getCurrentToken() of the consumer in the Message.getMetaData() under key MessageMetaData.FENCED_LOCK_TOKEN

Parameters:

messageConsumer - the message consumer. See PatternMatchingMessageHandler

Returns:

this outbox instance

setMessageConsumer

Outbox setMessageConsumer(Consumer<Message> messageConsumer)

Set the message consumer. To start consuming call startConsuming()

Parameters:

messageConsumer - the message consumer. See PatternMatchingMessageHandler

Returns:

this outbox instance

startConsuming

Outbox startConsuming()

Start consuming messages from the Outbox. Requires calling setMessageConsumer(Consumer) first
If an OrderedMessage is delivered via an Outbox using a FencedLock (such as Outboxes.durableQueueBasedOutboxes(DurableQueues, FencedLockManager) to coordinate message consumption, then you can find the FencedLock.getCurrentToken() of the consumer in the Message.getMetaData() under key MessageMetaData.FENCED_LOCK_TOKEN

Returns:

this outbox instance

stopConsuming

Outbox stopConsuming()

Stop consuming messages from the Outbox. Calling this method will remove the message consumer and to resume message consumption you need to call consume(Consumer)

Returns:

this outbox instance

hasAMessageConsumer

boolean hasAMessageConsumer()

Has the instance been created with a Message consumer or has consume(Consumer) been called

Returns:

Has the instance been created with a Message consumer or has consume(Consumer) been called

isConsumingMessages

boolean isConsumingMessages()

Is the provided Message consumer consuming messages from the Outbox

Returns:

Is the provided Message consumer consuming messages from the Outbox

name

OutboxName name()

The name of the outbox

Returns:

the name of the outbox

sendMessage

default Outbox sendMessage(Object payload)

Send a message (without meta-data) asynchronously.
This message will be stored durably (without any duplication check) in connection with the currently active UnitOfWork (or a new UnitOfWork will be created in case no there isn't an active UnitOfWork).
The message will be delivered asynchronously to the message consumer

Parameters:

payload - the message payload

Returns:

this outbox instance

sendMessage

default Outbox sendMessage(Object payload,
                           MessageMetaData metaData)

Send a message (with meta-data) asynchronously.
This message will be stored durably (without any duplication check) in connection with the currently active UnitOfWork (or a new UnitOfWork will be created in case no there isn't an active UnitOfWork).
The message will be delivered asynchronously to the message consumer

Parameters:

payload - the message payload

metaData - the message meta-data

Returns:

this outbox instance

sendMessage

Outbox sendMessage(Message message)

Send a message asynchronously.
This message will be stored durably (without any duplication check) in connection with the currently active UnitOfWork (or a new UnitOfWork will be created in case no there isn't an active UnitOfWork).
The message will be delivered asynchronously to the message consumer

Parameters:

message - the message

Returns:

this outbox instance

See Also:

OrderedMessage

getNumberOfOutgoingMessages

long getNumberOfOutgoingMessages()

Get the number of message in the outbox that haven't been sent yet

Returns:

Get the number of message in the outbox that haven't been sent yet