broker = decoder => ({
  nodeId: decoder.readInt32(),
  host: decoder.readString(),
  port: decoder.readInt32(),
  rack: decoder.readString(),
})
Metadata Response (Version: 1) => [brokers] controller_id [topic_metadata]
  brokers => node_id host port rack
    node_id => INT32
    host => STRING
    port => INT32
    rack => NULLABLE_STRING
  controller_id => INT32
  topic_metadata => topic_error_code topic is_internal [partition_metadata]
    topic_error_code => INT16
    topic => STRING
    is_internal => BOOLEAN
    partition_metadata => partition_error_code partition_id leader [replicas] [isr]
      partition_error_code => INT16
      partition_id => INT32
      leader => INT32
      replicas => INT32
      isr => INT32