content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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.oss.driver.api.core.metadata;
  
  import com.datastax.oss.driver.api.core.loadbalancing.LoadBalancingPolicy;
  import com.datastax.oss.driver.internal.core.metadata.TopologyEvent;
  import java.net.InetSocketAddress;
  
  /** The state of a node, as viewed from the driver. */
  public enum NodeState {
    /**
     * The driver has never tried to connect to the node, nor received any topology events about it.
     *
     * <p>This happens when nodes are first added to the cluster, and will persist if your {@link
     * LoadBalancingPolicy} decides to ignore them. Since the driver does not connect to them, the
     * only way it can assess their states is from topology events.
     */
    UNKNOWN,
    /**
     * A node is considered up in either of the following situations: 1) the driver has at least one
     * active connection to the node, or 2) the driver is not actively trying to connect to the node
     * (because it's ignored by the {@link LoadBalancingPolicy}), but it has received a topology event
     * indicating that the node is up.
     */
    UP,
    /**
     * A node is considered down in either of the following situations: 1) the driver has lost all
     * connections to the node (and is currently trying to reconnect), or 2) the driver is not
     * actively trying to connect to the node (because it's ignored by the {@link
     * LoadBalancingPolicy}), but it has received a topology event indicating that the node is down.
     */
    DOWN,
    /**
     * The node was forced down externally, the driver will never try to reconnect to it, whatever the
     * {@link LoadBalancingPolicy} says.
     *
     * <p>This is used for edge error cases, for example when the driver detects that it's trying to
     * connect to a node that does not belong to the Cassandra cluster (e.g. a wrong address was
     * provided in the contact points). It can also be {@link
     * TopologyEvent#forceDown(InetSocketAddress) triggered explicitly} by components (for example a
     * custom load balancing policy) that want to limit the number of nodes that the driver connects
     * to.
     */
    FORCED_DOWN,
  }
  