@Override
    public int scope() {
        return ENVOY_INSTANCE_METRIC;
    }
The envoy metrics. This group of metrics are in Prometheus metrics format family.
<p>
This metrics source supports Counter and Gauge types.
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/source/EnvoyInstanceMetric.java