project_id is not working for stackdriver workspace with multiple attached projects.

Hi !

first, thanks for your work !

We have an issue with project_id and workspace with multiple attached projects.

Here is our configuration

• main project is fsociety-prod, we created stackdriver workspace from this project
• secondary project is fsociety-preprod. When we create stackdriver workspace, we attached this project to previous workspace, instead of creating a new one.

Recently, we installed stackdriver-exporter.

When testing with project_id = fsociety-preprod, we collected metrics from fsociety-preprod project only. We were quite happy 👍

But when we deploy with project_id = fsociety-prod, we discovered that, with this conf, we collected all metrics from stackdriver workspace : metrics from two projects : fsociety-prod and fsociety-preprod.

How could we limit metrics from main project only ?

Thanks in advance !

Have a nice day

cc : @nlamirault

Start by reproducing the stackdriver-exporter configuration with a workspace containing fsociety-prod and fsociety-preprod, comparing project_id behavior for each value. Trace how project_id is applied to workspace metric collection; done means selecting fsociety-prod returns metrics from the main project only, without metrics from the attached project.