Re: Proprietary Replication Strategies: Cassandra Driver Support

[Vladimir Yudovin]

Well, it can be useful in some scenarios - e.g. temporary tables on nearest or 
the same node.

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




---- On Sat, 08 Oct 2016 13:44:00 -0400 Jeff Jirsa<jji...@gmail.com> 
wrote ---- 

I'm sure that's what he meant, I just disagree that it sounds useful 
 
-- 
Jeff Jirsa 
 
 
> On Oct 8, 2016, at 10:33 AM, Vladimir Yudovin <vla...@winguzone.com> 
wrote: 
> 
> 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 
> >> > 
> >> > 
> >> 
> >> 
> >> 
> >> 
> >> 
> >> 
> 
> 
> 
> 
>