Jon and Steve: I don't understand your point. The TokenAwareLoadBalancer identifies the nodes in the cluster that own the data for a particular token and route requests to one of them. As I understand it, the OP wants to send requests for a particular token to the same node every time (assuming it's available). How does that fail in a large cluster?
Jim On Tue, Apr 5, 2016 at 4:31 PM, Jonathan Haddad <j...@jonhaddad.com> wrote: > Yep - Steve hit the nail on the head. The odds of hitting the right > server with "sticky routing" goes down as your cluster size increases. You > end up adding extra network hops instead of using token aware routing. > > Unless you're trying to do a coordinator tier (and you're not, according > to your original post), this is a pretty bad idea and I'd advise you to > push back on that requirement. > > On Tue, Apr 5, 2016 at 12:47 PM Steve Robenalt <sroben...@highwire.org> > wrote: > >> Aside from Jon's "why" question, I would point out that this only really >> works because you are running a 3 node cluster with RF=3. If your cluster >> is going to grow, you can't guarantee that any one server would have all >> records. I'd be pretty hesitant to put an invisible constraint like that on >> a cluster unless you're pretty sure it'll only ever be 3 nodes. >> >> On Tue, Apr 5, 2016 at 9:34 AM, Jonathan Haddad <j...@jonhaddad.com> >> wrote: >> >>> Why is this a requirement? Honestly I don't know why you would do this. >>> >>> >>> On Sat, Apr 2, 2016 at 8:06 PM 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 >>>> >>> >> >> >> -- >> Steve Robenalt >> Software Architect >> sroben...@highwire.org <bza...@highwire.org> >> (office/cell): 916-505-1785 >> >> HighWire Press, Inc. >> 425 Broadway St, Redwood City, CA 94063 >> www.highwire.org >> >> Technology for Scholarly Communication >> >
