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public interface MetricsReporter extends Reconfigurable, AutoCloseable {
    [...]
    
    /**
     * Callback method providingProvides context metadata for the
     * service or library exposing metrics
     *
     * @param metricsContext the metric context
     */
    @InterfaceStability.Evolving
    default void contextChange(MetricsContext metricsContext) {}
}

/**
 * MetricsContext encapsulates additional metadata about metrics exposed via a
 * {@link org.apache.kafka.common.metrics.MetricsReporter}
 * 
 * The metadata map provides following information:
 * - a <code>_namespace</node> field indicating the component exposing metrics
 *   e.g. kafka.server, kafka.consumer
 *   {@link JmxReporter} uses this as prefix for mbean names
 *
 * - for clients and streams libraries: any freeform fields passed in via
 *   client properties in the form of `metrics.context.<key>=<value>
 *
 * - for kafka brokers: kafka.broker.id, kafka.cluster.id
 * - for connect workers: connect.kafka.cluster.id, connect.group.id
 */
@InterfaceStability.Evolving
public interface MetricsContext {

    /* predefined fields */
    String NAMESPACE = "_namespace"; // metrics namespace, formerly jmx prefix
    
    /**
     * Returns metadata fields
     */
    public Map<String, String> metadatacontextLabels();
}