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https://issues.apache.org/jira/browse/CASSANDRA-14557?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16553108#comment-16553108
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Joseph Lynch commented on CASSANDRA-14557:
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[~KurtG] I believe the current state of the patch is to provide the options and
implement {{SimpleStrategy}}. We need CASSANDRA-14303 I believe to add support
for {{NetworkTopologyStrategy}}. I think for CASSANDRA-14303 the default would
only apply only if no datacenters were given in the declaration at all, e.g.
{{{'class': 'NetworkTopologyStrategy'}}} would be equivalent to {{{'class':
'NetworkTopologyStrategy', 'default_datacenter_replication': 3}}}. The adding a
datacenter flow is covered in CASSANDRA-14303 but briefly it relies on the
autoexpansion only to happen at {{CREATE}} or {{ALTER}} time. If you don't
supply {{default_datacenter_replication}} but do supply explicit datacenters
everything works the same as in the past, if you do supply it then any
datacenters that exist but are not specified in the {{CREATE/ALTER}} statement
get that default value added. The minimum validation catches e.g. {{{'class':
'NetworkTopologyStrategy', 'default_datacenter_replication': 1}}}
Removing a datacenter is slightly trickier because of the minimum rf validation
(to remove a datacenter in the presence of {{default_datacenter_replication}}
you have to provide an excluded datacenter with RF=0), but I think it will
still work because the validation happens after we template out the replication
map.
> Consider adding default and required keyspace replication options
> -----------------------------------------------------------------
>
> Key: CASSANDRA-14557
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14557
> Project: Cassandra
> Issue Type: Improvement
> Components: Configuration
> Reporter: Sumanth Pasupuleti
> Assignee: Sumanth Pasupuleti
> Priority: Minor
> Labels: 4.0-feature-freeze-review-requested
> Fix For: 4.0
>
> Attachments: 14557-trunk.txt
>
>
> Ending up with a keyspace of RF=1 is unfortunately pretty easy in C* right
> now - the system_auth table for example is created with RF=1 (to take into
> account single node setups afaict from CASSANDRA-5112), and a user can
> further create a keyspace with RF=1 posing availability and streaming risks
> (e.g. rebuild).
> I propose we add two configuration options in cassandra.yaml:
> # {{default_keyspace_rf}} (default: 1) - If replication factors are not
> specified, use this number.
> # {{required_minimum_keyspace_rf}} (default: unset) - Prevent users from
> creating a keyspace with an RF less than what is configured
> These settings could further be re-used to:
> * Provide defaults for new keyspaces created with SimpleStrategy or
> NetworkTopologyStrategy (CASSANDRA-14303)
> * Make the automatic token [allocation
> algorithm|https://issues.apache.org/jira/browse/CASSANDRA-13701?focusedCommentId=16095662&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-16095662]
> interface more intuitive allowing easy use of the new token allocation
> algorithm.
> At the end of the day, if someone really wants to allow RF=1, they simply
> don’t set the setting. For backwards compatibility the default remains 1 and
> C* would create with RF=1, and would default to current behavior of allowing
> any RF on keyspaces.
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