public class RackAwareRoundRobinPolicy extends Object implements LoadBalancingPolicy
This policy provides round-robin queries over the node of the local rack. After that, the query plan includes round-robin list of nodes in the local DC (but not in local rack). It also includes in the query plans returned a configurable number of hosts in the remote data centers, but those are always tried after the local nodes. In other words, this policy guarantees that no host in a remote data center will be queried unless no host in the local data center can be reached.
|Modifier and Type
|Class and Description
Helper class to build the policy.
|Constructor and Description
|Modifier and Type
|Method and Description
Returns a builder to create a new instance.
Gets invoked at cluster shutdown.
Return the HostDistance for the provided host.
Initialize this load balancing policy.
Returns the hosts to use for a new query.
Called when a new node is added to the cluster.
Called when a node is determined to be down.
Called when a node is removed from the cluster.
Called when a node is determined to be up.
public static RackAwareRoundRobinPolicy.Builder builder()
public void init(Cluster cluster, Collection<Host> hosts)
Note that the driver guarantees that it will call this method exactly once per policy object and will do so before any call to another of the methods of the policy.
public HostDistance distance(Host host)
This policy consider nodes in the local datacenter as
LOCAL. For each remote
datacenter, it considers a configurable number of hosts as
REMOTE and the rest is
To configure how many hosts in each remote datacenter should be considered, see
The returned plan will always try each known host in the local rack first, and then, if none of the host in local rack are reachable, will try hosts in remote racks of the local datacenter. Finally, it will try up to a configurable number of other host per remote datacenter. The order of the local node in the returned query plan will follow a Round-robin algorithm.
newQueryPlan in interface
loggedKeyspace - the keyspace currently logged in on for this query.
statement - the query for which to build the plan.
public void onUp(Host host)
public void onDown(Host host)
public void onAdd(Host host)
The newly added node should be considered up.
public void onRemove(Host host)
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