Hi Radim,
Continuous query is built on top of these listeners. CQ _always_ needs
the previous value and it is very convenient in this case that the
command is forced to load the previous value. I imagine there may be
other use cases where we cannot live without the prev value.
I think the listener should be able to state if it needs the prev value
at registration time. Maybe add a new attribute in the Listener
annotation? Similar to how we handled Observation.
Adrian
On 08/19/2016 11:34 PM, Radim Vansa wrote:
Hi,
as I am trying to simplify current entry wrapping and distribution code,
I often find that listeners can get wrong previous value in the event,
and it sometimes forces the command to load the value even if it is not
needed for the command.
I am wondering if we should change the previous value in events to
Optional - we can usually at least detect that we cannot provide a
reliable value (e.g. after retry due to topology change, or because the
command did not bothered to load the previous value from cache loader)
and return empty Optional.
WDYT?
Radim