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A driver for DataStax Enterprise (DSE) and Apache Cassandra 1.2+ clusters that works exclusively with the Cassandra Query Language version 3 (CQL3) and Cassandra's binary protocol, supporting DSE-specific features such as geospatial types, DSE Graph and DSE authentication.

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/*
 * Copyright DataStax, Inc.
 *
 * This software can be used solely with DataStax Enterprise. Please consult the license at
 * http://www.datastax.com/terms/datastax-dse-driver-license-terms
 */
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).
 *
 * 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).
 *
 * 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
}