Cassandra Schema Management Tool

John Sanda jsanda at redhat.com
Fri May 24 16:02:03 UTC 2013


On May 24, 2013, at 11:46 AM, Stefan Negrea <snegrea at redhat.com> wrote:

> Hello Everybody,
> 
> Here are the design plans for the new Cassandra schema management tool:
> 
> 1) A version table will keep track of the current schema version
> 2) The initial setup
>  a) Will create:
>    i)Initial RHQ admin user/password
>    ii) RHQ keyspace
>    iii) Schema versioning column family (=table)
>  b) Once the initial setup is done, it will never run again
> 3) Everything else will be installed/updated via incremental changes:
> a) One change file per version change.
> b) Multiple changes can be bundled in a change file.
> c) The name of the change file will be used for database versioning purposes.
> d) If a change has already been applied it will not be applied again for the lifetime of the installation.
> e) If an incremental change fails, the upgrade process stops.
> f) The upgrade files will be in XML format, with a very simplistic XML Schema.
> 4) There will not be a single schema file for new installs.
> a) All installs will follow this incremental upgrade process.
> 5) All schema modifications outside of the schema manager will not be supported and are at risk.
> 
> 
> Starting with a simple and minimalist tool is the best solution (minimal set features, more robust). I expect the tool to evolve over time but if we keep things simple, then it will be to easier to maintain over time.
> 

Why do we need xml?


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