/*
* Copyright (C) 2012-2015 DataStax Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.datastax.driver.core;
/**
* The distance to a Cassandra node as assigned by a
* {@link com.datastax.driver.core.policies.LoadBalancingPolicy} (through its {@code
* distance} method).
* <p/>
* The distance assigned to an host influences how many connections the driver
* maintains towards this host. If for a given host the assigned {@code HostDistance}
* is {@code LOCAL} or {@code REMOTE}, some connections will be maintained by
* the driver to this host. More active connections will be kept to
* {@code LOCAL} host than to a {@code REMOTE} one (and thus well behaving
* {@code LoadBalancingPolicy} should assign a {@code REMOTE} distance only to
* hosts that are the less often queried).
* <p/>
* However, if a host is assigned the distance {@code IGNORED}, no connection
* to that host will maintained active. In other words, {@code IGNORED} should
* be assigned to hosts that should not be used by this driver (because they
* are in a remote data center for instance).
*/
public enum HostDistance {
// Note: PoolingOptions rely on the order of the enum.
LOCAL,
REMOTE,
IGNORED
}