Many C* versions back I did this by writing a custom snitch. This was to maximise use of the row cache but had the effect of pinning requests for a key to a given server. It sounds like you want to do the same thing but ignoring the key. In more modern reversions I believe this may be done as a load balancing policy.
I don't have the code handy but it was only a few dozen lines of Java, mostly boilerplate. IIRC the interface method just asks you to sort a list of IP addresses in your order of preference. Note that this only really does anything for the ONE consistency level. In any other level you'll end up hitting all 3 servers anyway. > On 02 Apr 2016, at 20:06, Mukil Kesavan <weirdbluelig...@gmail.com> wrote: > > Hello, > > We currently have 3 Cassandra servers running in a single datacenter with a > replication factor of 3 for our keyspace. We also use the SimpleSnitch wiith > DynamicSnitching enabled by default. Our load balancing policy is > TokenAwareLoadBalancingPolicy with RoundRobinPolicy as the child. This > overall configuration results in our client requests spreading equally across > our 3 servers. > > However, we have a new requirement where we need to restrict a client's > requests to a single server and only go to the other servers on failure of > the previous server. This particular use case does not have high request > traffic. > > Looking at the documentation the options we have seem to be: > > 1. Play with the snitching (e.g. place each server into its own DC or Rack) > to ensure that requests always go to one server and failover to the others if > required. I understand that this may also affect replica placement and we may > need to run nodetool repair. So this is not our most preferred option. > > 2. Write a new load balancing policy that also uses the HostStateListener for > tracking host up and down messages, that essentially accomplishes "sticky" > request routing with failover to other nodes. > > Is option 2 the only clean way of accomplishing our requirement? > > Thanks, > Micky
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