Why not synchronize on the client side? Make sure that the process that allocates user ids runs on only a single machine, in a synchronized method, and uses QUORUM for its reads and writes to Cassandra?
On Sun, Feb 6, 2011 at 11:02 PM, Aaron Morton <aa...@thelastpickle.com>wrote: > If you mix mysql and Cassandra you risk creating a single point of failure > around the mysql system. > > If you have use data that changes infrequently, a row cache in cassandra > will give you fast reads. > > Aaron > > On 5/02/2011, at 8:13 AM, Aklin_81 <asdk...@gmail.com> wrote: > > > Thanks so much Ryan for the links; I'll definitely take them into > > consideration. > > > > Just another thought which came to my mind:- > > perhaps it may be beneficial to store(or duplicate) some of the data > > like the Login credentials & particularly userId to User's Name > > mapping, etc (which is very heavily read), in a fast MyISAM table. > > This could solve the problem of keys though auto-generated unique & > > sequential primary keys. I could use the same keys for Cassandra rows > > for that user. And also since Cassandra reads are relatively slow, it > > makes sense to store data like userId to Name mapping in MyISAM as > > this data would be required after almost all queries to the database. > > > > Regards > > -Asil > > > > > > > > On Fri, Feb 4, 2011 at 10:14 PM, Ryan King <r...@twitter.com> wrote: > >> On Thu, Feb 3, 2011 at 9:12 PM, Aklin_81 <asdk...@gmail.com> wrote: > >>> Thanks Matthew & Ryan, > >>> > >>> The main inspiration behind me trying to generate Ids in sequential > >>> manner is to reduce the size of the userId, since I am using it for > >>> heavy denormalization. UUIDs are 16 bytes long, but I can also have a > >>> unique Id in just 4 bytes, and since this is just a one time process > >>> when the user signs-up, it makes sense to try cutting down the space > >>> requirements, if it is feasible "without any downsides"(!?). > >>> > >>> I am also using userIds to attach to Id of the other data of the user > >>> on my application. If I could reduce the userId size that I can also > >>> reduce the size of other Ids, I could drastically cut down the space > >>> requirements. > >>> > >>> > >>> [Sorry for this question is not directly related to cassandra but I > >>> think Cassandra factors here because of its tuneable consistency] > >> > >> Don't generate these ids in cassandra. Use something like snowflake, > >> flickr's ticket servers [2] or zookeeper sequential nodes. > >> > >> -ryan > >> > >> > >> 1. http://github.com/twitter/snowflake > >> 2. > http://code.flickr.com/blog/2010/02/08/ticket-servers-distributed-unique-primary-keys-on-the-cheap/ > >> >
