Re: Proprietary Replication Strategies: Cassandra Driver Support

[Jeff Jirsa]

That sounds awful, especially since you could just use SimpleStrategy with RF=1 
and then bootstrap / decom would handle resharding for you as expected.

-- 
Jeff Jirsa


> On Oct 8, 2016, at 10:09 AM, Edward Capriolo <edlinuxg...@gmail.com> wrote:
> 
> I have contemplated using LocalStrategy as a "do it yourself client side
> sharding system".
> 
> On Sat, Oct 8, 2016 at 12:37 AM, Vladimir Yudovin <vla...@winguzone.com>
> wrote:
> 
>> Hi Prasenjit,
>> I would like to get the replication factors of the key-spaces using the
>> strategies in the same way we get the replication factors for Simple and
>> NetworkTopology.
>> Actually LocalSarategy has no replication factor:
>> 
>> SELECT * FROM system_schema.keyspaces WHERE keyspace_name IN ('system',
>> 'system_schema');
>> keyspace_name | durable_writes | replication
>> ---------------+----------------+---------------------------
>> -----------------------------------------
>>        system       |                 True | {'class':
>> 'org.apache.cassandra.locator.LocalStrategy'}
>> system_schema |                 True | {'class':
>> 'org.apache.cassandra.locator.LocalStrategy'}
>> 
>> 
>> It's used for internal tables and not accessible to users:
>> 
>> CREATE KEYSPACE excel WITH replication = {'class': 'LocalStrategy'};
>> ConfigurationException: Unable to use given strategy class: LocalStrategy
>> is reserved for internal use.
>> 
>> 
>> Best regards, Vladimir Yudovin,
>> Winguzone - Hosted Cloud Cassandra on Azure and SoftLayer.
>> Launch your cluster in minutes.
>> 
>> 
>> 
>> 
>> ---- On Fri, 07 Oct 2016 17:06:09 -0400 Prasenjit
>> Sarkar&lt;prasenjit.sar...@datos.io&gt; wrote ----
>> 
>> Thanks Vlad and Jeremiah.
>> 
>> There were questions about support, so let me address that in more detail.
>> 
>> If I look at the latest Cassandra python driver, the support for
>> LocalStrategy is very limited (code snippet shown below) and the support
>> for EverywhereStrategy is non-existent. By limited I mean that the
>> Cassandra python driver only provides the name of the strategy for
>> LocalStrategy and not much else.
>> 
>> What I would like (and happy to help) is for the Cassandra python driver to
>> provide support for Local and Everywhere to the same extent it is provided
>> for Simple and NetworkTopology. I understand that token aware routing is
>> not applicable to either strategy but I would like to get the replication
>> factors of the key-spaces using the strategies in the same way we get the
>> replication factors for Simple and NetworkTopology.
>> 
>> Hope this helps,
>> Prasenjit
>> 
>> 
>> class LocalStrategy(ReplicationStrategy):
>> def __init__(self, options_map):
>> pass
>> def make_token_replica_map(self, token_to_host_owner, ring):
>> return {}
>> def export_for_schema(self):
>> """
>> Returns a string version of these replication options which are
>> suitable for use in a CREATE KEYSPACE statement.
>> """
>> return "{'class': 'LocalStrategy'}"
>> def __eq__(self, other):
>> return isinstance(other, LocalStrategy)
>> 
>> On Fri, Oct 7, 2016 at 11:56 AM, Jeremiah D Jordan &lt;
>> jeremiah.jor...@gmail.com&gt; wrote:
>> 
>> &gt; What kind of support are you thinking of? All drivers should support
>> them
>> &gt; already, drivers shouldn’t care about replication strategy except when
>> &gt; trying to do token aware routing.
>> &gt; But since anyone can make a custom replication strategy, drivers that
>> do
>> &gt; token aware routing just need to handle falling back to not doing
>> token
>> &gt; aware routing if a replication strategy they don’t know about is in
>> use.
>> &gt; All the open sources drivers I know of do this, so they should all
>> &gt; “support” those strategies already.
>> &gt;
>> &gt; -Jeremiah
>> &gt;
>> &gt; &gt; On Oct 7, 2016, at 1:02 PM, Prasenjit Sarkar &
>> lt;prasenjit.sar...@datos.io&gt;
>> &gt; wrote:
>> &gt; &gt;
>> &gt; &gt; Hi everyone,
>> &gt; &gt;
>> &gt; &gt; To the best of my understanding that Datastax has proprietary
>> replication
>> &gt; &gt; strategies: Local and Everywhere which are not part of the open
>> source
>> &gt; &gt; Apache Cassandra project.
>> &gt; &gt;
>> &gt; &gt; Do we know of any plans in the open source Cassandra driver
>> community to
>> &gt; &gt; support these two replication strategies? Would Datastax have a
>> licensing
>> &gt; &gt; concern if the open source driver community supported these
>> strategies?
>> &gt; I'm
>> &gt; &gt; fairly new here and would like to understand the dynamics.
>> &gt; &gt;
>> &gt; &gt; Thanks,
>> &gt; &gt; Prasenjit
>> &gt;
>> &gt;
>> 
>> 
>> 
>> 
>> 
>>