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.internal.core.metadata;
  
  import com.datastax.oss.driver.api.core.metadata.Node;
  import java.net.InetSocketAddress;
  import java.util.Objects;
  import net.jcip.annotations.Immutable;
  
  /**
   * An event emitted from the {@link TopologyMonitor}, indicating a change in the topology of the
   * Cassandra cluster.
   *
   * <p>Internally, the driver uses this to handle {@code TOPOLOGY_CHANGE} and {@code STATUS_CHANGE}
   * events received on the control connection; for historical reasons, those protocol events identify
   * nodes by their (untranslated) {@linkplain Node#getBroadcastRpcAddress() broadcast RPC address}.
   *
   * <p>As shown by the names, most of these events are mere suggestions, that the driver might choose
   * to ignore if they contradict other information it has about the nodes; see the documentation of
   * each factory method for detailed explanations.
   */
  @Immutable
  public class TopologyEvent {
  
    public enum Type {
      SUGGEST_UP,
      SUGGEST_DOWN,
      FORCE_UP,
      FORCE_DOWN,
      SUGGEST_ADDED,
      SUGGEST_REMOVED,
    }
  
    /**
     * Suggests that a node is up.
     *
     * <ul>
     *   <li>if the node is currently ignored by the driver's load balancing policy, this is reflected
     *       in the driver metadata's corresponding {@link Node}, for information purposes only.
     *   <li>otherwise:
     *       <ul>
     *         <li>if the driver already had active connections to that node, this has no effect.
     *         <li>if the driver was currently reconnecting to the node, this causes the current
     *             {@link
     *             com.datastax.oss.driver.api.core.connection.ReconnectionPolicy.ReconnectionSchedule}
     *             to be reset, and the next reconnection attempt to happen immediately.
     *       </ul>
     * </ul>
     */
    public static TopologyEvent suggestUp(InetSocketAddress broadcastRpcAddress) {
      return new TopologyEvent(Type.SUGGEST_UP, broadcastRpcAddress);
    }
  
    /**
     * Suggests that a node is down.
     *
     * <ul>
     *   <li>if the node is currently ignored by the driver's load balancing policy, this is reflected
     *       in the driver metadata's corresponding {@link Node}, for information purposes only.
     *   <li>otherwise, if the driver still has at least one active connection to that node, this is
     *       ignored. In other words, a functioning connection is considered a more reliable
     *       indication than a topology event.
     *       <p>If you want to bypass that behavior and force the node down, use {@link
     *       #forceDown(InetSocketAddress)}.
     * </ul>
     */
    public static TopologyEvent suggestDown(InetSocketAddress broadcastRpcAddress) {
      return new TopologyEvent(Type.SUGGEST_DOWN, broadcastRpcAddress);
    }
  
    /**
     * Forces the driver to set a node down.
     *
     * <ul>
     *   <li>if the node is currently ignored by the driver's load balancing policy, this is reflected
     *       in the driver metadata, for information purposes only.
     *   <li>otherwise, all active connections to the node are closed, and any active reconnection is
     *       cancelled.
     * </ul>
     *
     * In all cases, the driver will never try to reconnect to the node again. If you decide to
     * reconnect to it later, use {@link #forceUp(InetSocketAddress)}.
     *
     * <p>This is intended for deployments that use a custom {@link TopologyMonitor} (for example if
     * you do some kind of maintenance on a live node). This is also used internally by the driver
     * when it detects an unrecoverable error, such as a node that does not support the current
     * protocol version.
     */
    public static TopologyEvent forceDown(InetSocketAddress broadcastRpcAddress) {
      return new TopologyEvent(Type.FORCE_DOWN, broadcastRpcAddress);
    }
  
    /**
     * Cancels a previous {@link #forceDown(InetSocketAddress)} event for the node.
     *
     * <p>The node will be set back UP. If it is not ignored by the load balancing policy, a
     * connection pool will be reopened.
     */
    public static TopologyEvent forceUp(InetSocketAddress broadcastRpcAddress) {
      return new TopologyEvent(Type.FORCE_UP, broadcastRpcAddress);
    }
  
    /**
     * Suggests that a new node was added in the cluster.
     *
     * <p>The driver will ignore this event if the node is already present in its metadata, or if
     * information about the node can't be refreshed (i.e. {@link
     * TopologyMonitor#getNewNodeInfo(InetSocketAddress)} fails).
     */
    public static TopologyEvent suggestAdded(InetSocketAddress broadcastRpcAddress) {
      return new TopologyEvent(Type.SUGGEST_ADDED, broadcastRpcAddress);
    }
  
    /**
     * Suggests that a node was removed from the cluster.
     *
     * <p>The driver ignore this event if the node does not exist in its metadata.
     */
    public static TopologyEvent suggestRemoved(InetSocketAddress broadcastRpcAddress) {
      return new TopologyEvent(Type.SUGGEST_REMOVED, broadcastRpcAddress);
    }
  
    public final Type type;
  
    /**
     * Note that this is the <em>untranslated</em> broadcast RPC address, as it was received in the
     * protocol event.
     *
     * @see Node#getBroadcastRpcAddress()
     */
    public final InetSocketAddress broadcastRpcAddress;
  
    /** Builds a new instance (the static methods in this class are a preferred alternative). */
    public TopologyEvent(Type type, InetSocketAddress broadcastRpcAddress) {
      this.type = type;
      this.broadcastRpcAddress = broadcastRpcAddress;
    }
  
    public boolean isForceEvent() {
      return type == Type.FORCE_DOWN || type == Type.FORCE_UP;
    }
  
    @Override
    public boolean equals(Object other) {
      if (other == this) {
        return true;
      } else if (other instanceof TopologyEvent) {
        TopologyEvent that = (TopologyEvent) other;
        return this.type == that.type
            && Objects.equals(this.broadcastRpcAddress, that.broadcastRpcAddress);
      } else {
        return false;
      }
    }
  
    @Override
    public int hashCode() {
      return Objects.hash(this.type, this.broadcastRpcAddress);
    }
  
    @Override
    public String toString() {
      return "TopologyEvent(" + type + ", " + broadcastRpcAddress + ")";
    }
  }
  