Metrics service (proto)
service.metrics.v3.StreamMetricsResponse
service.metrics.v3.StreamMetricsMessage
[service.metrics.v3.StreamMetricsMessage proto]
{
  "identifier": {...},
  "envoy_metrics": []
}
- identifier
- (service.metrics.v3.StreamMetricsMessage.Identifier) Identifier data effectively is a structured metadata. As a performance optimization this will only be sent in the first message on the stream. 
- envoy_metrics
- (repeated .io.prometheus.client.MetricFamily) A list of metric entries 
service.metrics.v3.StreamMetricsMessage.Identifier
[service.metrics.v3.StreamMetricsMessage.Identifier proto]
{
  "node": {...}
}
- node
- (config.core.v3.Node, REQUIRED) The node sending metrics over the stream.