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From Suranjan Kumar <suranjan.ku...@gmail.com>
Subject Re: [DISCUSS] TTL setting on WAN
Date Mon, 25 Mar 2019 23:53:33 GMT
Hi,
 I think the one approach for a user would be to 'filter' the events while
dispatching. If I remember correctly, we can attach a filter at dispatch
time and filter the events based on creationTime of the GatewayEvent. We
can provide a pre created filter and use it based on some so that user
doesn't have to write his/her own.

Something like,
/**
All the events which spend timeToLive or more time in queue will be deleted
from the queue
and will not be sent to remote site.
Possible consequence is that two sites can be inconsistent in case
*/
public GatewaySenderFactory setEntryTimeToLive(long timeToLive);

As queues will be read in LRU way this would be faster too. Only drawback
is that there will be only one thread (not sure if we have concurrent
dispatcher yet) clearing the queue.

As Udo/Dan mentioned above, user needs to be aware of the consequences.


On Tue, Mar 26, 2019 at 3:09 AM Bruce Schuchardt <bschuchardt@pivotal.io>
wrote:

> I've walked through the code to forward expiration actions to async
> event listeners & don't see how to apply it to removal of queue entries
> for WAN.  The current implementation just queues the expiration
> actions.  If we wanted to remove any queued events associated with the
> expired region entry we'd have to scan the whole queue, which would be
> too slow if we're overflowing the queue to disk.
>
> I've also walked through the conflation code.  It applies only to the
> current batch being processed by the gateway sender.  The data structure
> used to perform conflation is just a Map that is created in the sender's
> batch processing method and then thrown away.
>
> On 3/20/19 11:15 AM, Dan Smith wrote:
> >> 2) The developer wants to replicate _state_.  This means that implicit
> >> state changes (expiration or eviction w/ destroy) could allow us to
> >> optimize the queue size.  This is very similar to conflation, just a
> >> different kind of optimization.
> >>
> >> For this second case, does it make sense to allow the user to specify a
> >> different TTL than the underlying region?  It seems like what the user
> >> wants is to not replicate stale data and having an extra TTL attribute
> >> would just be another value to mis-configure.  What do you think about
> just
> >> providing a boolean flag?
> >>
> >>
> > This kinda jogged my memory. AsyncEventQueues actually *do* have a
> boolean
> > flag to allow you to forward expiration events to the queue. I have no
> idea
> > how this interacts with conflation though -
> >
> https://geode.apache.org/releases/latest/javadoc/org/apache/geode/cache/asyncqueue/AsyncEventQueueFactory.html#setForwardExpirationDestroy-boolean-
> >
>

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