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From David Boxenhorn <da...@lookin2.com>
Subject Re: Using a synchronized counter that keeps track of no of users on the application & using it to allot UserIds/ keys to the new users after sign up
Date Mon, 07 Feb 2011 08:26:18 GMT
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 <aaron@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 <asdkl93@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 <ryan@twitter.com> wrote:
> >> On Thu, Feb 3, 2011 at 9:12 PM, Aklin_81 <asdkl93@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/
> >>
>

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