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From "Jonathan Ellis (JIRA)" <>
Subject [jira] Commented: (CASSANDRA-44) It isn't possible to easily add new column families to an existing cluster
Date Wed, 08 Apr 2009 21:12:13 GMT


Jonathan Ellis commented on CASSANDRA-44:

Maintaining CF definitions looks like a good use case for Zookeeper to me.  We could do it
like this:

 - on startup, a cassandra node must contact zookeeper and read the column family data.  this
is the only time it will abort if ZK is not available.
 - when an operation is requested for a columnfamily that does not exist, the node checks
zookeeper to see if that column has been added
 - additionally, we can check every hour or so for new columns and removed columns.  so removed
CFs could accept ops for a while after officially being "removed." 
 - adding and removing CFs would be done with a web interface.  (I'm strongly in favor of
moving the web UI to Jython; it's much better suited for this than raw Java.)

At the znode level, we would have /columfamilies/[tablename]/[columnfamily1|columnfamily2|...]
where the columnfamily znodes contain the sort information and any other attributes that was
previously being stored in TableMetadata.

Notes to keep adminning a ZK ensemble relatively painless:

 - use the Cassandra seed nodes as the ZK ensemble members.  (Both seed nodes and ZK require
a relatively small number of machines in the cluster to participate.)  We can ship a config
file so that cassandra will continue to Just Work on localhost.


> It isn't possible to easily add new column families to an existing cluster
> --------------------------------------------------------------------------
>                 Key: CASSANDRA-44
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Eric Evans
>            Priority: Minor
> Once a cluster is created, adding new column families to the configuration file will
not result in their creation. See also:

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