you mention never deleting from the queue, so what purpose is this serving? (if you don't pop off the front, is it really a queue?)
seems if guaranteed order of messages is required, there are many other projects which are focused towards that problem (rabbitmq, kestrel, activemq, etc) or am i misunderstanding your needs here? -keith On Thu, Apr 1, 2010 at 6:32 PM, Jeremy Davis <jerdavis.cassan...@gmail.com> wrote: > I'm in the process of implementing a Totally Ordered Queue in Cassandra, and > wanted to bounce my ideas off the list and also see if there are any other > suggestions. > > I've come up with an external source of ID's that are always increasing (but > not monotonic), and I've also used external synchronization to ensure only > one writer to a given queue. And I handle de-duping in the app. > > > My current solution is : (simplified) > > Use the "QueueId", to Key into a row of a CF. > Then, every column in that CF corresponds to a new entry in the Queue, with > a custom Comparator to sort the columns by my external ID that is always > increasing. > > Technically I never delete data from the Queue, and I just page through it > from a given ID using a SliceRange, etc. > > Obviously the problem being that the row needs to get compacted. so then I > started bucketizing with multiple rows for a given queue (for example one > per day (again I'm simplifying))...(so the Key is now "QueueId+Day"...) > > Does this seem reasonable? It's solvable, but is starting to seem > complicated to implement... It would be very easy if I didn't have to have > multiple buckets.. > > > > My other thought is to store one entry per row, and perform get_range_slices > and specify a KeyRange, with the OrderPreservingPartitioner. > But it isn't exactly clear to me what the Order of the keys are in this > system, so I don't know how to construct my key and queries appropriately... > Is this Lexical String Order? Or? > > So for example.. Assuming my QueueId's are longs, and my ID's are also > longs.. My key would be (in Java): > > long queueId; > long msgId; > > key = "" + queueId + ":" + msgId; > > And if I wanted to do a query my key range might be from > start = "" + queueId + ":0" > end = "" + queueId + ":" + Long.MAX_VALUE; > > (Will I have to left pad the msgIds with 0's)? > > And is this going to be efficient if my msgId isn't monotonically > increasing? > > Thanks, > -JD > > > > > > > > > > > > >
