--- title: Metric overview: A template that represents a single runtime metric. location: https://istio.io/docs/reference/config/template/metric.html layout: protoc-gen-docs number_of_entries: 2 ---

The `metric` template is designed to let you describe runtime metric to dispatch to monitoring backends.

## Template

The `metric` template represents a single piece of data to report.

When writing the configuration, the value for the fields associated with this template can either be a literal or an expression. Please note that if the datatype of a field is not istio.mixer.adapter.model.v1beta1.Value, then the expression’s inferred type must match the datatype of the field.

Example config:

    apiVersion: "config.istio.io/v1alpha2"
    kind: metric
    metadata:
      name: requestsize
      namespace: istio-system
    spec:
      value: request.size | 0
      dimensions:
        source_service: source.service | "unknown"
        source_version: source.labels["version"] | "unknown"
        destination_service: destination.service | "unknown"
        destination_version: destination.labels["version"] | "unknown"
        response_code: response.code | 200
      monitored_resource_type: '"UNSPECIFIED"'

Field | Type | Description
--- | --- | ---
`value` | `istio.mixer.adapter.model.v1beta1.Value` | The value being reported.
`dimensions` | `map<string, istio.mixer.adapter.model.v1beta1.Value>` | The unique identity of the particular metric to report.
`monitoredResourceType` | `string` | Optional. An expression to compute the type of the monitored resource this metric is being reported on. If the metric backend supports monitored resources, these fields are used to populate that resource. Otherwise these fields will be ignored by the adapter.
`monitoredResourceDimensions` | `map<string, istio.mixer.adapter.model.v1beta1.Value>` | Optional. A set of expressions that will form the dimensions of the monitored resource this metric is being reported on. If the metric backend supports monitored resources, these fields are used to populate that resource. Otherwise these fields will be ignored by the adapter.

## istio.mixer.adapter.model.v1beta1.Value

Value is used inside templates for fields that have dynamic types. The actual datatype of the field depends on the datatype of the expression used in the operator configuration.