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The "ArchitectureInternals" page has been changed by PeterSchuller. The comment on this change is: AbstractNetworkTopologySnitch does the proximity sorting, not NetworkToplogyStrategy. http://wiki.apache.org/cassandra/ArchitectureInternals?action=diff&rev1=24&rev2=25 -------------------------------------------------- * !StorageProxy then sorts, by asking the endpoint snitch, the responsible nodes by "proximity". * The definition of "proximity" is up to the endpoint snitch * With a SimpleSnitch, proximity directly corresponds to proximity on the token ring. - * With the NetworkTopologySnitch, endpoints that are in the same rack are always considered "closer" than those that are not. Failing that, endpoints in the same data center are always considered "closer" than those that are not. + * With implementations based on AbstractNetworkTopologySnitch (such as PropertyFileSnitch), endpoints that are in the same rack are always considered "closer" than those that are not. Failing that, endpoints in the same data center are always considered "closer" than those that are not. * The DynamicSnitch, typically enabled in the configuration, wraps whatever underlying snitch (such as SimpleSnitch and NetworkTopologySnitch) so as to dynamically adjust the perceived "closeness" of endpoints based on their recent performance. This is in an effort to try to avoid routing traffic to endpoints that are slow to respond. * !StorageProxy then arranges for messages to be sent to nodes as required: * The closest node (as determined by proximity sorting as described above) will be sent a command to perform an actual data read (i.e., return data to the co-ordinating node).
