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 org.apache.kafka.metadata;
  
  import java.util.HashMap;
  import java.util.Map;
  
  /**
   * The broker state.
   *
   * The numeric values used here are part of Kafka's public API.  They appear in metrics,
   * and are also sent over the wire in some cases.
   *
   * The expected state transitions are:
   *
   * NOT_RUNNING
   *     ↓
   * STARTING
   *     ↓
   * RECOVERY
   *     ↓
   * RUNNING
   *     ↓
   * PENDING_CONTROLLED_SHUTDOWN
   *     ↓
   * SHUTTING_DOWN
   */
  public enum BrokerState {
      /**
       * The state the broker is in when it first starts up.
       */
      NOT_RUNNING((byte) 0),
  
      /**
       * The state the broker is in when it is catching up with cluster metadata.
       */
      STARTING((byte) 1),
  
      /**
       * The broker has caught up with cluster metadata, but has not yet
       * been unfenced by the controller.
       */
      RECOVERY((byte) 2),
  
      /**
       * The state the broker is in when it has registered at least once, and is
       * accepting client requests.
       */
      RUNNING((byte) 3),
  
      /**
       * The state the broker is in when it is attempting to perform a controlled
       * shutdown.
       */
      PENDING_CONTROLLED_SHUTDOWN((byte) 6),
  
      /**
       * The state the broker is in when it is shutting down.
       */
      SHUTTING_DOWN((byte) 7),
  
      /**
       * The broker is in an unknown state.
       */
      UNKNOWN((byte) 127);
  
      private static final Map<Byte, BrokerState> VALUES_TO_ENUMS = new HashMap<>();
  
      static {
          for (BrokerState state : BrokerState.values()) {
              VALUES_TO_ENUMS.put(state.value(), state);
          }
      }
  
      private final byte value;
  
      BrokerState(byte value) {
          this.value = value;
      }
  
      public static BrokerState fromValue(byte value) {
          BrokerState state = VALUES_TO_ENUMS.get(value);
          if (state == null) {
              return UNKNOWN;
          }
          return state;
      }
  
      public byte value() {
          return value;
      }
  }
  