(google-cloud-spanner) Built-in metrics fail when one process uses databases in different projects

まず、google-cloud-spanner 3.68.0 を使用して、提供されている 2 プロジェクトの例を実行し、spanner.Client が使用する組み込みメトリクスのパスを調べます。デフォルトの動作を SPANNER_DISABLE_BUILTIN_METRICS および Client(disable_builtin_metrics=True) と比較し、その後、エクスポート中に最初のクライアントのプロジェクトがどのように再利用されるかを追跡します。組み込みメトリクスを無効にせずに、各データベースのメトリクスがそれぞれのプロジェクトに届けば完了です。

Environment details

• OS type and version: Linux (also happens on macOS)
• Python version: 3.13
• google-cloud-spanner version: 3.68.0

Steps to reproduce

1. In one process, create two clients for databases in two different projects.
2. Run a query on each.
3. Wait a minute for the metrics export.

Code example

from google.cloud import spanner

a = spanner.Client(project="project-a")
b = spanner.Client(project="project-b")

a.instance("i").database("d").snapshot().execute_sql("SELECT 1")
b.instance("i").database("d").snapshot().execute_sql("SELECT 1")

What happens

The metrics export fails, and no metrics show up in Cloud Monitoring for either project:

InvalidArgument: 400 Field resource.labels.project_id had an invalid value of
"project-b": if present, must be the project number or ID in the request name
(projects/project-a).

Whichever client is created first decides where all metrics go, so everything from the other project is rejected — and it takes the first project's metrics down with it, since they're sent in the same request.

What I expected

Metrics for each database go to that database's project. Running against several projects is pretty normal, and right now it means no built-in metrics at all.

What I tried

SPANNER_DISABLE_BUILTIN_METRICS=true and Client(disable_builtin_metrics=True) both work, but only by giving up the metrics. As far as I can tell there's no way to pass in my own exporter or meter provider, so there's no way to keep them. Java has this (googleapis/google-cloud-java#13679) and there's an open request for Go (googleapis/google-cloud-go#11204), but I couldn't find anything similar here.