feat: Add google.universe-domain flag for custom GoogleCloud universes (#430)

This commit introduces a new command-line flag `--google.universe-domain`
which allows users to specify the Google Cloud universe to use.
This is useful for users who are not using the default `googleapis.com`
 universe.

The default value for this flag is "googleapis.com".

Updates include:
- Addition of the `--google.universe-domain` flag to the CLI options.
- Documentation for the new flag in `README.md`.
- A feature entry in `CHANGELOG.md`.

Signed-off-by: Mathieu Goulin <matgou1@msn.com>

Author: matgou

CHANGELOG.md

@@ -1,5 +1,7 @@
 ## master / unreleased
 
+- [FEATURE] Add `google.universe-domain` flag to specify the Google Cloud universe to use.
+
 ## 0.18.0 / 2025-01-16
 
 - [FEATURE] Support more specific prefixes in ?collect parameter #387

README.md

@@ -80,6 +80,7 @@ If you are still using the legacy [Access scopes][access-scopes], the `https://w
 | ----------------------------------- | -------- |---------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
 | `google.project-ids`                 | No       | GCloud SDK auto-discovery | Repeatable flag of Google Project IDs                                                                                                                                                        |
 | `google.projects.filter`            | No       |                           | GCloud projects filter expression. See more [here](https://cloud.google.com/sdk/gcloud/reference/projects/list).                                                                                                                                                        |
+| `google.universe-domain`            | No       | `googleapis.com`          | Target specific Google Cloud environments, such as public cloud, or specific sovereign clouds                                  |
 | `monitoring.metrics-ingest-delay`   | No       |                           | Offsets metric collection by a delay appropriate for each metric type, e.g. because bigquery metrics are slow to appear                                                                           |
 | `monitoring.drop-delegated-projects` | No       | No                        | Drop metrics from attached projects and fetch `project_id` only.                                                                                                                                  |
 | `monitoring.metrics-prefixes`  | Yes      |                           | Repeatable flag of Google Stackdriver Monitoring Metric Type prefixes (see [example][metrics-prefix-example] and [available metrics][metrics-list])                                                  |

stackdriver_exporter.go

@@ -68,6 +68,10 @@ var (
 		"google.projects.filter", "Google projects search filter.",
 	).String()
 
+	googleUniverseDomain = kingpin.Flag(
+		"google.universe-domain", "The Cloud universe to use.",
+	).Default("googleapis.com").String()
+
 	stackdriverMaxRetries = kingpin.Flag(
 		"stackdriver.max-retries", "Max number of retries that should be attempted on 503 errors from stackdriver.",
 	).Default("0").Int()
@@ -169,7 +173,7 @@ func createMonitoringService(ctx context.Context) (*monitoring.Service, error) {
 		rehttp.ExpJitterDelay(*stackdriverBackoffJitterBase, *stackdriverMaxBackoffDuration), // Set timeout to <10s as that is prom default timeout
 	)
 
-	monitoringService, err := monitoring.NewService(ctx, option.WithHTTPClient(googleClient))
+	monitoringService, err := monitoring.NewService(ctx, option.WithHTTPClient(googleClient), option.WithUniverseDomain(*googleUniverseDomain))
 	if err != nil {
 		return nil, fmt.Errorf("Error creating Google Stackdriver Monitoring service: %v", err)
 	}