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From Ben Hood <0x6e6...@gmail.com>
Subject Re: Writes during schema migration
Date Mon, 23 Dec 2013 23:54:20 GMT
Hey Aaron,

Thanks for following up on this one.

I guess you're right and in any case, you're unlikely to want two
different versions of the code running at the same time.

Cheers,

Ben

On Mon, Dec 23, 2013 at 5:42 PM, Aaron Morton <aaron@thelastpickle.com> wrote:
> It depends a little on the nature of the change, but you need some
> coordination between the schema change and your code. e.g. add new column,
> change code to write to it or add new column, change code to use new column
> and not old column, remove old column.
>
> Cheers
>
> -----------------
> Aaron Morton
> New Zealand
> @aaronmorton
>
> Co-Founder & Principal Consultant
> Apache Cassandra Consulting
> http://www.thelastpickle.com
>
> On 19/12/2013, at 3:02 am, Ben Hood <0x6e6562@gmail.com> wrote:
>
> Hi,
>
> I was wondering if anybody knows any best practices of how to apply a
> schema migration across a cluster.
>
> I've been reading this article:
>
> http://www.datastax.com/dev/blog/the-schema-management-renaissance
>
> to see what is happening under the covers. However the article doesn't
> seem to talk about concurrent write access during the migration
> process.
>
> I'm naively assuming that you'd need to block all writes to the
> cluster before the migration is started. This is would be firstly
> because of potential consistency issues amongst the cluster nodes. But
> this would also be because you'd need two versions of your app to
> running at the same time.
>
> Does anybody have any experience with doing this kind of thing?
>
> Cheers,
>
> Ben
>
>

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