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 java.util.Map;
  
  /**
   * MetricsContext encapsulates additional contextLabels about metrics exposed via a
   * {@link org.apache.kafka.common.metrics.MetricsReporter}
   *
   * <p>The {@link #contextLabels()} map provides following information:
   * <dl>
   *   <dt>in all components</dt>
   *   <dd>a {@code _namespace} field indicating the component exposing metrics
   *   e.g. kafka.server, kafka.consumer.
   *   The {@link JmxReporter} uses this as prefix for MBean names</dd>
   *
   *   <dt>for clients and streams libraries</dt>
   *   <dd>any freeform fields passed in via
   *   client properties in the form of {@code metrics.context.<key>=<value>}</dd>
   *
   *   <dt>for kafka brokers</dt>
   *   <dd>kafka.broker.id, kafka.cluster.id</dd>
   *
   *   <dt>for connect workers</dt>
   *   <dd>connect.kafka.cluster.id, connect.group.id</dd>
   * </dl>
   */
  public interface MetricsContext {
      /* predefined fields */
      String NAMESPACE = "_namespace"; // metrics namespace, formerly jmx prefix
  
      /**
       * Returns the labels for this metrics context.
       *
       * @return the map of label keys and values; never null but possibly empty
       */
      Map<String, String> contextLabels();
  }
  