// API version of the referent
  // +optional
  optional string apiVersion = 3;
}

// ExternalMetricSource indicates how to scale on a metric not associated with
// any Kubernetes object (for example length of queue in cloud
// messaging service, or QPS from loadbalancer running outside of cluster).
// Exactly one "target" type should be set.
message ExternalMetricSource {
  // metricName is the name of the metric in question.

  // Message written is intended to be brief final status, such as an assertion failure message.
  // Will be truncated by the node if greater than 4096 bytes. The total message length across
  // all containers will be limited to 12kb.
  // Defaults to /dev/termination-log.
  // Cannot be updated.
  // +optional
  optional string terminationMessagePath = 13;