Update main.tf

[PaggieChen]

fix(iam): resolve null service identity email error

Refactor service agent identity logic to use deterministic email construction.

Calculate service agent emails using ${project_number} to bypass API race conditions.

Add explicit depends_on between project services and IAM members.

Standardize Compute Engine default service account retrieval.

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[gemini-code-assist]

Summary of Changes

Hello @PaggieChen, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a critical issue where service agent identity emails could be null due to race conditions during API calls. It refactors the core logic for constructing service agent emails to be deterministic, leveraging the project number for consistent generation. Furthermore, it introduces explicit dependencies between key resource types, such as project service enablement, service identity creation, and IAM role assignments, to guarantee that all necessary components are fully initialized before subsequent operations. This significantly enhances the stability and reliability of resource provisioning within the module.

Highlights

• Deterministic Service Agent Email Construction: Service agent emails are now constructed deterministically using the project number, which helps to prevent 'null service identity email' errors caused by API race conditions during resource creation. This involves using a new data source for google_project to retrieve the project number.
• Standardized Compute Engine Default Service Account Retrieval: The method for retrieving the Compute Engine default service account has been standardized and integrated into the new deterministic email construction logic.
• Explicit Dependency Management: Explicit depends_on attributes have been added to google_project_service_identity, data.google_compute_default_service_account, and google_project_iam_member resources. This ensures that project services are enabled, service identities are created/retrieved, and IAM roles are assigned in the correct order, mitigating race conditions and improving provisioning reliability.

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[gemini-code-assist]

Code Review

This pull request refactors the service agent identity logic to use deterministic email construction, which is a good approach to avoid race conditions and issues with values not being known during Terraform's plan phase. The explicit depends_on clauses added to various resources also improve the robustness of the module by enforcing the correct order of resource creation.

However, I've found a critical issue with the implementation of the deterministic email construction. The current logic assumes a single, common format for service agent emails, which is not correct for all GCP services. This will cause the module to fail when used with services like BigQuery or Cloud Storage that use a different email format. My review includes a detailed comment and a code suggestion to address this by handling exceptions for different email formats.

[gemini-code-assist]

The deterministic construction of service agent emails assumes a single format (service-...@gcp-sa-...), which is not universally true for all Google Cloud services. This will cause failures for services with different service agent email formats, such as BigQuery or Cloud Storage.

To make this more robust, you could use a map of exceptions for services that don't follow the common pattern. Here is a suggested implementation using lookup to handle these exceptions. You may want to expand this map with other known exceptions.

  service_agent_emails = {
    for i in var.activate_api_identities :
    i.api => i.api == "compute.googleapis.com" ?
      data.google_compute_default_service_account.default[0].email :
      lookup(
        {
          "bigquery.googleapis.com" = "bq-${data.google_project.project.number}@bigquery-iam.gserviceaccount.com",
          "storage.googleapis.com"  = "service-${data.google_project.project.number}@gs-project-accounts.iam.gserviceaccount.com"
        },
        i.api,
        "service-${data.google_project.project.number}@gcp-sa-${replace(i.api, ".googleapis.com", "")}.iam.gserviceaccount.com"
      )
  }