DescribeConfigs Request (Version: 1) => [resource [config_name]] include_synonyms
  resource => resource_type resource_name
    resource_type => INT8
    resource_name => STRING
  config_name => STRING
  include_synonyms => BOOLEAN

DescribeConfigs Response (Version: 1) => throttle_time_ms [entities]
  throttle_time_ms => INT32
  entities => error_code error_message resource [configs]
    error_code => INT16
    error_message => STRING
    resource => resource_type resource_name
      resource_type => INT8
      resource_name => STRING
    configs => [config_entry [synonym]]    <= Added [synonym]
    config_entry =>
      config_name => STRING
      config_value => NULLABLE_STRING
      read_only => BOOLEAN
      config_source => INT8                <= Replaced boolean is_default with more generic config_source (see below for values)
      is_sensitive => BOOLEAN
    synonym =>                             <= NEW
      config_name => STRING
      config_value => NULLABLE_STRING
      config_source => INT8                <= may be one of (TOPIC|DYNAMIC_BROKER|DYNAMIC_DEFAULT_BROKER|STATIC_BROKER|DEFAULT)

package org.apache.kafka.common;

import java.util.Map;
import java.util.Set;

/**
 * Interface for reconfigurable classes that support dynamic configuration.
 */
public interface Reconfigurable extends Configurable {

    /**
     * Returns the names of configs that may be reconfigured.
     */
    Set<String> reconfigurableConfigs();

    /**
     * Validates the provided configuration. The provided map contains
     * all configs including any reconfigurable configs that may be different
     * from the initial configuration.
     */
    boolean validate(Map<String, ?> configs);

   /**
     * Reconfigures this instance with the given key-value pairs. The provided
     * map contains all configs including any reconfigurable configs that
     * may have changed since the object was initially configured using
     * {@link Configurable#configure(Map)}.
     */
    void reconfigure(Map<String, ?> configs);

}

/**
 * Return true if synonym configs should be returned in the response.
 */
public boolean includeSynonyms() {
    return includeSynonyms;
}

/**
 * Set to true if synonym configs should be returned in the response.
 */
public DescribeConfigsOptions includeSynonyms(boolean includeSynonyms) {
    this.includeSynonyms = includeSynonyms;
    return this;
}

/**
 * Returns all config values that may be used as the value of this config along with their source,
 * in the order of precedence. The list starts with the value returned in this ConfigEntry.
 * The list is empty if synonyms were not requested using {@link DescribeConfigsOptions#includeSynonyms(boolean)}. 
 */
public List<ConfigSynonym> synonyms() {
    return  synonyms;
}

public static class ConfigSynonym {

    /**
     * Returns the name of this configuration.
     */
    public String name() {
        return name;
    }

    /**
     * Returns the value of this configuration, which may be null if the configuration is sensitive.
     */
    public String value() {
        return value;
    }

    /**
     * Returns the source of this configuration.
     */
    public ConfigSource source() {
        return source;
    }
}

public enum ConfigSource {
    TOPIC_CONFIG,                   // dynamic topic config that is configured for a specific topic
    DYNAMIC_BROKER_CONFIG,          // dynamic broker config that is configured for a specific broker
    DYNAMIC_DEFAULT_BROKER_CONFIG,  // dynamic broker config that is configured as default for all brokers in the cluster
    STATIC_BROKER_CONFIG,           // static broker config provided as broker properties at start up (e.g. server.properties file)
    DEFAULT_CONFIG                  // built-in default configuration for configs that have a default value
}