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From "Stu Hood (JIRA)" <>
Subject [jira] Commented: (CASSANDRA-1066) DatacenterShardStrategy needs enforceable and keyspace based RF
Date Thu, 29 Jul 2010 16:22:18 GMT


Stu Hood commented on CASSANDRA-1066:

* Comment in conf/cassandra.yaml refers to IReplicaPlacementStrategy
* Neither strategy_class nor strategy_class_options should allow nulls in Avro's KsDef: a
map should default to empty, and strategy_class should always be set.
* Some commented printlns made it into dht.Range, TMD, CFSTest
* Why override AbstractReplicationStrategy.equals?
* The "datacenters changed, clearing endpoint cache" in DCShardStrategy shouldn't be necessary
* Can you rename the static version of StorageService.getReplicationStrategy to 'create*'?
It looks like it is only for use by client code

Otherwise, looks good to me.

> 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: 0.7.0
>         Attachments: 1066-changes-patch.txt, 1066-external.patch, 1066.txt, 1066.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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