Is it possible to deduplicate messages sent to the agent's queue?

[svetlyak40wt]

For example, I have an agent which renders the static site.

When some event has happened, it's handler sends agent a message to rerender the site. However when there are already a :rerender message in the queue I don't want to add another one - otherwise when there are many events, rerender will happen to often.

So I need an actor which will discard some messages sent to it with a code like this:

(sento.actor:tell actor message)

It whould be wonderful, if there will be some way to preprocess message to decide if the message should be discarded, because my message is the list where first item is a keyword (action name) and the rest are arguments such as site id, config, etc and I want to consider only action name and site id for deduplcation.

[mdbergmann]

Hi.

The easiest and probably best way that comes to mind would be to use a mailbox/queue that implements this functionality.
There is no such mailbox right now. But I think, if performance is not super critical, it'd be relatively easy to make a subclass of bt mailbox that use a queue that can filter already existing entries by some provided filter function. Maybe there is such a queue as a library already.

From there the current implementation allows to create a dedicated dispatcher by specifying the custom :mbox-type as key parameter. But this would have to be a dispatcher with a single actor or the deduplication wouldn't work.
Unfortunately for actors of :pinned type the :mbox-type parameter does not apply (would be a good addition though).

[mdbergmann]

There might be a work-around to use this :mbox-type on a single actor.
But this still requires a dummy dispatcher like: (:dedup (:workers 0)), then you can create single actors using actor-of :dispatcher :dedup :mbox-type 'my-dedup-mbox.

(untested)

[svetlyak40wt]

Interesting. Will try this approach.

[svetlyak40wt]

@mdbergmann please, take a look at this PR: #111

It adds support for mbox-type for pinned dispatchers and also makes it possible to use a custom function to create a dispatcher instance.