Update docs for GCP detector (open-telemetry#17864)

processor/resourcedetectionprocessor/README.md

@@ -103,46 +103,75 @@ processors:
  override: false
 ```
 
-### GCE Metadata
+### GCP Metadata
 
 Uses the [Google Cloud Client Libraries for Go](https://github.com/googleapis/google-cloud-go)
-to read resource information from the [GCE metadata server](https://cloud.google.com/compute/docs/storing-retrieving-metadata) to retrieve the following resource attributes:
-
- * cloud.provider ("gcp")
- * cloud.platform ("gcp_compute_engine")
- * cloud.account.id
- * cloud.region
- * cloud.availability_zone
- * host.id
- * host.image.id
- * host.type
+to read resource information from the [metadata server](https://cloud.google.com/compute/docs/storing-retrieving-metadata) and environment variables to detect which GCP platform the
+application is running on, and detect the appropriate attributes for that platform. Regardless
+of the GCP platform the application is running on, use the gcp detector:
 
 Example:
 
 ```yaml
 processors:
- resourcedetection/gce:
- detectors: [env, gce]
+ resourcedetection/gcp:
+ detectors: [env, gcp]
  timeout: 2s
  override: false
 ```
 
-### GKE: Google Kubernetes Engine
+#### GCE Metadata
 
  * cloud.provider ("gcp")
- * cloud.platform ("gcp_gke")
- * k8s.cluster.name (name of the GKE cluster)
+ * cloud.platform ("gcp_compute_engine")
+ * cloud.account.id (project id)
+ * cloud.region (e.g. us-central1)
+ * cloud.availability_zone (e.g. us-central1-c)
+ * host.id (instance id)
+ * host.name (instance name)
+ * host.type (machine type)
 
-Example:
+#### GKE Metadata
 
-```yaml
-processors:
- resourcedetection/gke:
- detectors: [env, gke]
- timeout: 2s
- override: false
-```
+ * cloud.provider ("gcp")
+ * cloud.platform ("gcp_kubernetes_engine")
+ * cloud.account.id (project id)
+ * cloud.region (only for regional GKE clusters; e.g. "us-central1")
+ * cloud.availability_zone (only for zonal GKE clusters; e.g. "us-central1-c")
+ * k8s.cluster.name
+ * host.id (instance id)
+ * host.name (instance name; only when workload identity is disabled)
+
+#### Google Cloud Run Metadata
 
+ * cloud.provider ("gcp")
+ * cloud.platform ("gcp_cloud_run")
+ * cloud.account.id (project id)
+ * cloud.region (e.g. "us-central1")
+ * faas.id (instance id)
+ * faas.name (service name)
+ * faas.version (service revision)
+
+#### Google Cloud Functions Metadata
+
+ * cloud.provider ("gcp")
+ * cloud.platform ("gcp_cloud_functions")
+ * cloud.account.id (project id)
+ * cloud.region (e.g. "us-central1")
+ * faas.id (instance id)
+ * faas.name (function name)
+ * faas.version (function version)
+
+#### Google App Engine Metadata
+
+ * cloud.provider ("gcp")
+ * cloud.platform ("gcp_app_engine")
+ * cloud.account.id (project id)
+ * cloud.region (e.g. "us-central1")
+ * cloud.availability_zone (e.g. "us-central1-c")
+ * faas.id (instance id)
+ * faas.name (service name)
+ * faas.version (service version)
 
 ### AWS EC2