Message Queue is often not a great use case for Cassandra. For information on how to handle high delete workloads see http://www.datastax.com/dev/blog/leveled-compaction-in-apache-cassandra
It hard to create a model without some idea of the data load, but I would suggest you start with: CF: UserMessages Key: ReceiverID Columns : column name = TimeUUID ; column value = message ID and Body That will order the messages by time. Depending on load (and to support deleting a previous months messages) you may want to partition the rows by month: CF: UserMessagesMonth Key: ReceiverID+YYYYMM Columns : column name = TimeUUID ; column value = message ID and Body Everything the same as before. But now a user has a row for each month and which you can delete as a whole. This also helps avoid very big rows. > I really don't think that storage will be an issue, I have 2TB per nodes, > messages are 1KB limited. I would suggest you keep the per node limit to 300 to 400 GB. It can take a long time to compact, repair and move the data when it gets above 400GB. Hope that helps. ----------------- Aaron Morton Freelance Developer @aaronmorton http://www.thelastpickle.com On 27/04/2012, at 1:30 AM, Morgan Segalis wrote: > Hi everyone ! > > I'm fairly new to cassandra and I'm not quite yet familiarized with column > oriented NoSQL model. > I have worked a while on it, but I can't seems to find the best model for > what I'm looking for. > > I have a Erlang software that let user connecting and communicate with each > others, when an user (A) sends > a message to a disconnected user (B), it stores it on the database and wait > for the user (B) to connect and retrieve > the message queue, and deletes it. > > Here's some key point : > - Users are identified by integer IDs > - Each message are unique by combination of : Sender ID - Receiver ID - > Message ID - time > > I have a queue Message, and here's the operations I would need to do as fast > as possible : > > - Store from 1 to X messages per registered user > - Get the number of stored messages per user (Can be a incremental variable > updated at each store // this is often retrieved) > - retrieve all messages from an user at once. > - delete all messages from an user at once. > - delete all messages that are older than Y months (from all users). > > I really don't think that storage will be an issue, I have 2TB per nodes, > messages are 1KB limited. > I'm really looking for speed rather than storage optimization. > > My configuration is 2 dedicated server which are both : > - 4 x Intel i7 2.66 Ghz > - 64 bits > - 24 Go > - 2 TB > > Thank you all.
