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.common.metrics;
  
  import org.apache.kafka.common.Reconfigurable;
  import org.apache.kafka.common.config.ConfigException;
  
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  /**
   * A plugin interface to allow things to listen as new metrics are created so they can be reported.
   * <p>
   * Implement {@link org.apache.kafka.common.ClusterResourceListener} to receive cluster metadata once it's available. Please see the class documentation for ClusterResourceListener for more information.
   */
  public interface MetricsReporter extends Reconfigurable, AutoCloseable {
  
      /**
       * This is called when the reporter is first registered to initially register all existing metrics
       * @param metrics All currently existing metrics
       */
      void init(List<KafkaMetric> metrics);
  
      /**
       * This is called whenever a metric is updated or added
       * @param metric The metric that has been added or changed
       */
      void metricChange(KafkaMetric metric);
  
      /**
       * This is called whenever a metric is removed
       * @param metric The metric that has been removed
       */
      void metricRemoval(KafkaMetric metric);
  
      /**
       * Called when the metrics repository is closed.
       */
      void close();
  
      // default methods for backwards compatibility with reporters that only implement Configurable
      default Set<String> reconfigurableConfigs() {
          return Collections.emptySet();
      }
  
      default void validateReconfiguration(Map<String, ?> configs) throws ConfigException {
      }
  
      default void reconfigure(Map<String, ?> configs) {
      }
  
      /**
       * Sets the context labels for the service or library exposing metrics. This will be called before {@link #init(List)} and may be called anytime after that.
       *
       * @param metricsContext the metric context
       */
      default void contextChange(MetricsContext metricsContext) {
      }
  }
  