Re: Re: Proprietary Replication Strategies: Cassandra Driver Support

[Vladimir Yudovin]

As far as I understand Edward meant to have option determinate actual storage 
node on client side, by driver, disregarding key hash/tokens mechanism.

Best regards, Vladimir Yudovin, 
Winguzone - Hosted Cloud Cassandra on Azure and SoftLayer.
Launch your cluster in minutes.




---- On Sat, 08 Oct 2016 13:17:14 -0400 Jeff Jirsa <jji...@gmail.com> 
wrote ---- 

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<prasenjit.sar...@datos.io> 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 < 
>> jeremiah.jor...@gmail.com> wrote: 
>> 
>> > What kind of support are you thinking of? All drivers should 
support 
>> them 
>> > already, drivers shouldn’t care about replication strategy 
except when 
>> > trying to do token aware routing. 
>> > But since anyone can make a custom replication strategy, 
drivers that 
>> do 
>> > token aware routing just need to handle falling back to not 
doing 
>> token 
>> > aware routing if a replication strategy they don’t know about 
is in 
>> use. 
>> > All the open sources drivers I know of do this, so they 
should all 
>> > “support” those strategies already. 
>> > 
>> > -Jeremiah 
>> > 
>> > > On Oct 7, 2016, at 1:02 PM, Prasenjit Sarkar & 
>> lt;prasenjit.sar...@datos.io> 
>> > wrote: 
>> > > 
>> > > Hi everyone, 
>> > > 
>> > > To the best of my understanding that Datastax has 
proprietary 
>> replication 
>> > > strategies: Local and Everywhere which are not part 
of the open 
>> source 
>> > > Apache Cassandra project. 
>> > > 
>> > > Do we know of any plans in the open source Cassandra 
driver 
>> community to 
>> > > support these two replication strategies? Would 
Datastax have a 
>> licensing 
>> > > concern if the open source driver community 
supported these 
>> strategies? 
>> > I'm 
>> > > fairly new here and would like to understand the 
dynamics. 
>> > > 
>> > > Thanks, 
>> > > Prasenjit 
>> > 
>> > 
>> 
>> 
>> 
>> 
>> 
>>