docs: router setup for Datadog

docs/source/reference/router/telemetry/metrics-exporters/datadog.mdx

@@ -8,27 +8,58 @@ Enable and configure the [OTLP exporter](/router/configuration/telemetry/exporte
 
 For general tracing configuration, refer to [Router Metrics Configuration](/router/configuration/telemetry/exporters/metrics/overview).
 
-## Datadog configuration
+## Configuration 
 
-To export metrics to Datadog, you must both: 
+To export metrics to Datadog, you must configure both the router to send traces to the Datadog agent and the Datadog agent to accept OpenTelemetry Protocol (OTLP) metrics.
 
-- Configure the Datadog agent to accept OpenTelemetry Protocol (OTLP) metrics, and
-- Configure the router to send traces to the Datadog agent.
+### Router configuration
 
-### Datadog agent configuration
+The router should set attributes that Datadog uses to organize its APM view and other UI:
 
-To configure the Datadog agent, add OTLP configuration (`otlp_config`) to your `datadog.yaml`. For example:
+- `otel.name`: span name that's fixed for Datadog
+- `resource.name`: Datadog resource name that's displayed in traces
+- `operation.name`: Datadog operation name that populates a dropdown menu in the Datadog service page
 
-```yaml title="datadog.yaml"
-otlp_config:
-  receiver:
-    protocols:
-      grpc:
-        endpoint: <dd-agent-ip>:4317
+You should add these attributes to your `router.yaml` configuration file. The example below sets these attributes for the `router`, `supergraph`, and `subgraph` stages of the router's request lifecycle:
+
+```yaml title="router.yaml"
+telemetry:
+  instrumentation:
+    spans:
+      mode: spec_compliant
+      router:
+        attributes:
+          otel.name: router
+          operation.name: "router"
+          resource.name:
+            request_method: true
+
+      supergraph:
+        attributes:
+          otel.name: supergraph
+          operation.name: "supergraph"
+          resource.name:
+            operation_name: string
+
+      subgraph:
+        attributes:
+          otel.name: subgraph
+          operation.name: "subgraph"
+          resource.name:
+            subgraph_operation_name: string
 ```
 
-### Router configuration
-To configure the router, enable the [OTLP exporter](/router/configuration/telemetry/exporters/metrics/otlp#configuration) and set both `temporality: delta` and `endpoint: <datadog-agent-endpoint>`. For example: 
+Consequently you can filter for these operations in Datadog APM:
+
+<img
+  className="screenshot"
+  alt="Datadog APM showing operations set with example attributes set in router.yaml"
+  src="../../../../images/router/datadog-apm-ops-example.png"
+  width="600"
+/>
+
+
+You should also enable the [OTLP exporter](/router/configuration/telemetry/exporters/metrics/otlp#configuration) and set both `temporality: delta` and `endpoint: <datadog-agent-endpoint>`. For example: 
 
 ```yaml title="router.yaml"
 telemetry:
@@ -44,9 +75,20 @@ telemetry:
 
 <Note>
 
-**You must set `temporality: delta`**, otherwise the router generates incorrect metrics.
+You must set `temporality: delta`, otherwise the router generates incorrect metrics.
 
 </Note>
 
-For more details about Datadog configuration, see [Datadog's docs on Agent configuration](https://docs.datadoghq.com/opentelemetry/otlp_ingest_in_the_agent/?tab=host).
+### Datadog agent configuration
 
+To configure the Datadog agent, add OTLP configuration (`otlp_config`) to your `datadog.yaml`. For example:
+
+```yaml title="datadog.yaml"
+otlp_config:
+  receiver:
+    protocols:
+      grpc:
+        endpoint: <dd-agent-ip>:4317
+```
+
+For more details about Datadog configuration, see [Datadog's docs on Agent configuration](https://docs.datadoghq.com/opentelemetry/otlp_ingest_in_the_agent/?tab=host).