Hi, We are working on defining the ring topology for our cluster. One of the plans under discussion is to have a RF=2 and perform read/write operations with CL=ONE. I know this could be an issue since it doesn't satisfy R+W > RF. This will work if we can always force the clients to go to the first node responsible for the data and go to its replica only if the first node is not available.
For eg assume the ring is following with token space from 0 to 100. Assume random parititioner is used. A[0] -> B[25] -> C[50] -> D[75] so going by SimpleStrategy, the replica for A will be B, for B it will be C and so on. What I am looking for is: 1. Some way to send requests for keys whose token fall between 0-25 to B and never to C even though C will have the data due to it being replica of B. 2. Only when B is down or not reachable, the request should go to C. 3. Once the requests start going to C, they should continue unless C is down and in which case the requests should then go to B. My understanding is that SimpleSnitch should fit here except for the enforcing #3 above. I should be able to extend the SimpleSnitch to add the behavior described in #3 above. Question is will SimpleSnitch come into picture if the request from client reaches node C directly? If yes, will it proxy request to B? I don't want C to serve request for keys in range 0-25 unless B is down. One way this can be feasible is if I do key -> token -> node mapping in my client. But this might get messy as I will have to keep track of nodes in the ring etc. Comments/suggestions are welcome. Thanks, Naren
