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=doc #16874 clean up Relationship between deliver and confirmDelivery section

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pkaczor 2015-02-20 09:07:43 +01:00
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akka-docs/rst/java/lambda-persistence.rst
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@ -422,22 +422,21 @@ this will send the message to the destination actor. When recovering, messages w
Once recovery has completed, if there are outstanding messages that have not been confirmed (during the message replay),
the persistent actor will resend these before sending any other messages.
Deliver also requires a function to pass the ``deliveryId`` into the message. A ``deliveryId`` is required to acknowledge
receipt of a message, and is also used in playback, when the actor is recovering so that messages received can be correctly acknowledged.
A function can be created to map your own ``messageId`` to ``deliveryId``, which may come from your own domain model.
This function must keep track of which ``messageId`` have been acknowledged.
Alternatively, the Persistence module provides a default sequence number implementation which can also be used as the ``deliveryId``
for messages. The default sequence increases monotonically, without gaps.
Deliver requires a ``deliveryIdToMessage`` function to pass the provided ``deliveryId`` into the message so that correlation
between ``deliver`` and ``confirmDelivery`` is possible. The ``deliveryId`` must do the round trip. Upon receipt
of the message, destination actor will send the same``deliveryId`` wrapped in a confirmation message back to the sender.
The sender will then use it to call ``confirmDelivery`` method to complete delivery routine.
.. includecode:: ../../../akka-samples/akka-sample-persistence-java-lambda/src/main/java/doc/LambdaPersistenceDocTest.java#at-least-once-example
Correlation between ``deliver`` and ``confirmDelivery`` is performed with the ``deliveryId`` that is provided
as parameter to the ``deliveryIdToMessage`` function. The ``deliveryId`` is typically passed in the message to the
destination, which replies with a message containing the same ``deliveryId``.
The ``deliveryId`` is a strictly monotonically increasing sequence number without gaps. The same sequence is
used for all destinations of the actor, i.e. when sending to multiple destinations the destinations will see
gaps in the sequence if no translation is performed.
The ``deliveryId`` generated by the persistence module is a strictly monotonically increasing sequence number
without gaps. The same sequence is used for all destinations of the actor, i.e. when sending to multiple
destinations the destinations will see gaps in the sequence. It is not possible to use custom ``deliveryId``.
However, you can send a custom correlation identifier in the message to the destination. You must then retain
a mapping between the internal ``deliveryId`` (passed into the ``deliveryIdToMessage`` function) and your custom
correlation id (passed into the message). You can do this by storing such mapping in a ``Map(correlationId -> deliveryId)``
from which you can retrive the ``deliveryId`` to be passed into the ``confirmDelivery`` method once the receiver
of your message has replied with your custom correlation id.
The ``AbstractPersistentActorWithAtLeastOnceDelivery`` class has a state consisting of unconfirmed messages and a
sequence number. It does not store this state itself. You must persist events corresponding to the