Clarify google managed prometheus troubleshooting guide (open-telemet…

…ry#34986)

Adding all resource attributers as metric labels can produce more
problems than it solves if, for example, resource attributes are too
long.

Fixes
GoogleCloudPlatform/opentelemetry-operations-go#887

Instead, recommend adding a set of common known identifying attributes.

exporter/googlemanagedprometheusexporter/README.md

@@ -280,13 +280,21 @@ logic from OpenTelemetry resource to Google Cloud's `prometheus_target`
 monitored resouce didn't preserve a resource attribute that was needed to
 distinguish timeseries. This can be mitigated by adding resource
 attributes as metric labels using `resource_filters` configuration in the
-exporter:
+exporter. The following example adds common identifying resource attributes.
+You may need to expand this list with other resource attributes to fix
+duplicate timeseries errors:
 
 ```yaml
   googlemanagedprometheus:
     metric:
       resource_filters:
-        regex: ".*"
+      - prefix: "cloud"
+      - prefix: "k8s"
+      - prefix: "faas"
+      - regex: "container.id"
+      - regex: "process.pid"
+      - regex: "host.name"
+      - regex: "host.id"
 ```
 
 If you need to troubleshoot errors further, start by filtering down to a single

exporter/googlemanagedprometheusexporter/config_test.go

@@ -8,6 +8,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/GoogleCloudPlatform/opentelemetry-operations-go/exporter/collector"
 	"github.com/GoogleCloudPlatform/opentelemetry-operations-go/exporter/collector/googlemanagedprometheus"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -54,6 +55,29 @@ func TestLoadConfig(t *testing.T) {
 						},
 					},
 					Prefix: "my-metric-domain.com",
+					ResourceFilters: []collector.ResourceFilter{
+						{
+							Prefix: "cloud",
+						},
+						{
+							Prefix: "k8s",
+						},
+						{
+							Prefix: "faas",
+						},
+						{
+							Regex: "container.id",
+						},
+						{
+							Regex: "process.pid",
+						},
+						{
+							Regex: "host.name",
+						},
+						{
+							Regex: "host.id",
+						},
+					},
 				},
 			},
 			QueueSettings: exporterhelper.QueueSettings{

exporter/googlemanagedprometheusexporter/testdata/config.yaml

@@ -20,6 +20,14 @@ exporters:
       extra_metrics_config:
         enable_target_info: false
         enable_scope_info: false
+      resource_filters:
+      - prefix: "cloud"
+      - prefix: "k8s"
+      - prefix: "faas"
+      - regex: "container.id"
+      - regex: "process.pid"
+      - regex: "host.name"
+      - regex: "host.id"
 
 
 service: