Affinity key for specific node

[Mikael]

Hi!

I have a singleton service running on a specific node, It access a 
serial port so it must be running on that specific node so I can't use 
affinity key for the service, now I want to create some values in a 
cache that will be used by the service, is there any way I can create 
affinity keys for those values so they will end up in the cache on the 
same node as the service ?