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From "Gary Dusbabek (JIRA)" <>
Subject [jira] Commented: (CASSANDRA-1066) DatacenterShardStrategy needs enforceable and keyspace based RF
Date Wed, 23 Jun 2010 21:15:51 GMT


Gary Dusbabek commented on CASSANDRA-1066:

* CS should use SS.instance.getTokenMetadata() instead of creating a new one.
* the factory calls the old implicit constructor and then init().  Is this an improvement
over just adding a map to the constructor args, and then having the constructor (if needed)
do the work in init?  Having an init() method opens up the API to abuse (when should[n't]
I call init, etc.?).  I'm in favor of just amending the implicit constructors.
* fix all the todos. :)

> DatacenterShardStrategy needs enforceable and keyspace based RF
> ---------------------------------------------------------------
>                 Key: CASSANDRA-1066
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Jeremy Hanna
>            Assignee: Jeremy Hanna
>            Priority: Minor
>             Fix For: 0.7
>         Attachments: 1066-changes-patch.txt
> Currently, the DatacenterShardStrategy reads in a properties file -
- to get a per-datacenter replication factor.  So any keyspace that is using the DSS in the
cluster is using that same properties file to configure its replication factor.  The implementation
doesn't take into account the per-keyspace replication factor, but it is assumed that the
sum of all the datacenter RF values equals the per-keyspace replication value that is part
of the keyspace metadata.
> It seems that an improvement could be two-fold:
> 1. Enforce the replication factor for the keyspace as always equal the sum of all the
datacenter RF values.  Otherwise, if they aren't equal, bad things (tm) can happen.
> 2. Make the datacenter RF values part of the keyspace metadata rather than a global value.
 Again, currently if any keyspace in the cluster is configured to use DSS, it will be using
the global DC RF values found in the properties file.  An improvement could be to instead
of having the properties file, configure that on a per keyspace basis.  That would make the
cluster more multi-tenant friendly so it could be flexible with multiple keyspaces.

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