update resource attributes used by prometheus, and round-trip other r…

…esource attributes

specification/metrics/datamodel.md

@@ -1177,11 +1177,9 @@ The following attributes MUST be associated with scraped metrics as resource att
 | OTLP Resource Attribute | Description |
 | ----------------------- | ----------- |
 | `service.name` | The configured name of the service that the target belongs to |
-| `job` | Identical to `service.name` |
-| `instance` | The <host>:<port> of the target's URL that was scraped. |
-| `host.name` | `instance` The <host> portion of `instance` |
-| `port` | `instance` The <port> portion of `instance` |
-| `scheme` | `http` or `https` |
+| `net.host.name` | The <host> portion of the target's URL that was scraped |
+| `net.host.port` | The <port> portion of the target's URL that was scraped |
+| `http.scheme` | `http` or `https` |
 
 ### OTLP Metric points to Prometheus
 
@@ -1240,9 +1238,13 @@ OpenTelemetry Metric Attributes MUST be converted to [Prometheus labels](https:/
 
 #### Resource Attributes
 
-In SDK Prometheus (pull) exporters, all resource attributes MUST be dropped, and MUST NOT be attached as labels. The scraper of the endpoint is expected to discover resource attributes of the endpoint it is scraping.
+In SDK Prometheus (pull) exporters, resource attributes SHOULD be converted to the [`target_info`](https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#supporting-target-metadata-in-both-push-based-and-pull-based-systems) metric, or MUST be dropped, and MUST NOT be attached as labels to other metrics. The `target_info` metric MUST info-typed metric whose labels MUST include the resource attributes, and MUST NOT include any other labels. There MUST be at most one `target_info` metric exposed on a Prometheus endpoint.
 
-In the Collector's Prometheus pull and push (remote-write) exporters, it is possible for metrics from multiple targets to be sent together, so targets must be disambiguated from one another.  However, the Prometheus exposition format and [remote-write](https://github.com/Prometheus/Prometheus/blob/main/prompb/remote.proto) formats do not include a notion of resource, and expect metric labels to distinguish scraped targets.  By convention, [`job` and `instance`](https://Prometheus.io/docs/concepts/jobs_instances/#jobs-and-instances) labels distinguish targets and are expected to be present on metrics exposed on a Prometheus pull exporter (a ["federated"](https://Prometheus.io/docs/Prometheus/latest/federation/) Prometheus endpoint) or pushed via Prometheus remote-write. In the collector Prometheus exporters, the `job` and `instance` resource attributes MUST be converted to Prometheus metric labels, and other resource attributes SHOULD NOT be converted to metric labels.
+In the Collector's Prometheus pull and push (remote-write) exporters, it is possible for metrics from multiple targets to be sent together, so targets must be disambiguated from one another.  However, the Prometheus exposition format and [remote-write](https://github.com/Prometheus/Prometheus/blob/main/prompb/remote.proto) formats do not include a notion of resource, and expect metric labels to distinguish scraped targets.  By convention, [`job` and `instance`](https://Prometheus.io/docs/concepts/jobs_instances/#jobs-and-instances) labels distinguish targets and are expected to be present on metrics exposed on a Prometheus pull exporter (a ["federated"](https://Prometheus.io/docs/Prometheus/latest/federation/) Prometheus endpoint) or pushed via Prometheus remote-write. In the collector Prometheus exporters, the `service.name` attribute MUST be converted to the `job` metric label, and the `net.host.name` and `net.host.port` attributes, if present, MUST be converted to the `instance` label as `<net.host.name>:<net.host.port>`. If `job` and `instance` are successfully added, other resource attributes SHOULD be converted to a [`target_info`](https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#supporting-target-metadata-in-both-push-based-and-pull-based-systems) metric, or MUST be dropped. The `target_info` metric is an info-typed metric whose labels MUST include the resource attributes, and MUST NOT include any other labels other than `job` and `instance`.  There MUST be at most one `target_info` metric exported for each unique combination of `job` and `instance`.
+
+If info-typed metrics are not yet supported by the language Prometheus client library, a gauge-typed metric named `target_info` with a constant value of 1 MUST be used instead.
+
+To convert OTLP resource attributes to Prometheus labels, string Attribute values are converted directly to labels, and non-string Attribute values MUST be converted to string attributes following the [attribute specification](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/common/common.md#attribute).
 
 ## Footnotes