Location Aware Replication in Voldemort

[rahul]

Hey Guys ,

I was wondering, if Voldemort supports location aware replication or is there anyway custom logic can be incorporated for prioritizing replication to nodes of other region or is there any other way to achieve that ? Also, does Voldemort has feature similar to dynamic snitch (snitch identifies which nodes have poor read latency and re-routes the request to some other node) in cassandra ?

Thanks,

./Rahul

[Vinoth C]

Hi Rahul,

No Voldemort does not have any feature similar to snitch. But how Voldemort handles degraded servers, could potentially provide behaviour similar to that. Essentially, if the Voldemort client (which also embeds the router) observes bad latency, it will mark the node down for a period of time and keep retrying in the background and include it back in again.. (and this process repeats)

I am not sure what you mean by "prioritizing for replication"? In theory, you can write  a custom routing strategy and plug it in to determine how you choose replicas.

[Rahul R]

Hey Vinod, 

Is there any sample program where a custom replica could be plugged in ? Or could you give me a walkthrough of things (how to pluging my custom logic into voldemort )I will have to do for that ?

./Rahul

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[Vinoth C]

Well.. I am not sure if this has been done before so I don't have sample programs.. I can give you pointers on how to go about this if you like..

For starters, you would need to add a new type here
https://github.com/voldemort/voldemort/blob/master/src/java/voldemort/routing/RoutingStrategyType.java

and if you trace how consistent-routing or zone-routing is used, a pattern should emerge. Basically, you would need to implement the RoutingStrategy interface.. and use the type name you added in the stores.xml.