How to implement a messaging system?

> Dear list
>
> (I guess this follows on from my previous posts...)
>
> I'm trying to set up a simple messaging system using Magma, to enable users to pass messages to one another.  I considered creating a 'mailbox' Collection for each user, in which messages could be stored, and which could be polled at regular intervals to check for new messages.
>
> However, since each session has its own view of this object, any other user/session dropping a message into the Collection would violate the rule 'do not share objects between MagmaSession instances'.
>
> What is the proper way to implement such a system?  I'd be very grateful for any insight!
>
> Amir
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> Because for user A and user B, each accessing the one persistent model
> via Session A and Session B, respectively, A would add Message-A to
> B's 'collection' which he accessed from his session.  After B
> refreshed his session, his view of the model would reflect his own
> copy of Message-A in his own copy of B's 'collection'.
>
> > What is the proper way to implement such a system?  I'd be very grateful for any insight!
>
> What you said should work just fine.  Use MagmaCollections with an
> index on the timestamp so you don't have to worry about
> commit-conflicts.

> > I originally thought to create a mailbox for each user in a MagmaPreallocatedDictionary, with the association User -> OrderedCollection (where 'User' is an instance of class 'User', so each item would be unique).
>
> Why are you wanting to use a MagmaPreallocatedDictionary to hold
> Users?  How many users are in the system and how fast do they need
> access to their list of new messages?
>
> When I pull up my mail client, it takes a couple of seconds for my
> Inbox to be displayed.  This is analagous to using a MagmaCollection
> for each user's message.
>
> Recall what I said MagmaCollections were designed for:  For end-user
> query requirements, which is exactly the case you've stated:  A user
> comes to check on their messages.  So a MagmaCollection is perfectly
> appropriate for that, not a MagmaPreallocatedDictionary.
>
> I don't know how many users you will have, but given the extremely
> simple access requirements, you could put htem into a MagmaCollection
> as well.
>
> So, you have one MC for "AllUsers" and then one MC for each user
> containing that users messages.
>
> > So, checking up on one's own mailbox would simply entail finding oneself's User in the Dictionary and reading the associated collection of messages.
> >
> > However, if another user were to drop a message into this collection, the same OrderedCollection would have to be accessed by another session.  Isn't this a no-no, even with refreshing a session?
>
> I'm wondering what you mean by "the same OrderedCollection".  The same
> one in the database?  Or the same one in image memory?
>
> Yes, it will be the same one in the database, but it will be different
> ones in image memory if they are retrieved by different sessions.
>
> >
> > Are you suggesting to use MagmaCollections instead of OrderedCollections?  Isn't that far more 'expensive', especially since each user on the system would be assigned such a collection just to hold their messages?
>
> MagmaCollections consume more resources than a OrderedCollection, yes,
> but the reason I stated was that it would allow multiple messages to
> come into the same user and avoid a commit-conflict.
>
>  - Chris