How to implement a messaging system?

[Amir Ansari]

OK, I made the system far more complex than necessary; your comments about the suitability of MagmaCollection made everything clear.  It'll work fine now.

Actually, I started this simply enough, in exactly the way you suggested, but using OrderedCollection - and when it didn't work properly I complicated everything instead of simply using a MagmaCollection.

Thanks for your help Chris!

And, of course, thanks for your comments Facu.

Amir


On Mon, 3 Jan 2011 12:33:11 -0600
Chris Muller <asqueaker at gmail.com> wrote:

> > 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