Hashicorp Vault

Optimizing Vault Costs with serviceaccount_name for Identity Aliases

Hashicorp Vault SaaS bills on client usage, and a client is everything from a user to a machine. More on this here. The problem is that when a developer removes a chart and redeploys it, vault will count the Kubernetes ServiceAccount as a distinct new app, which isn’t quite true, because it’s the same app we had before and we were billed for.

When configuring Vault with Kubernetes authentication, the alias_name_source parameter plays a critical role in defining how identity aliases are generated. By default, Vault uses serviceaccount_uid, but switching to serviceaccount_name can significantly reduce costs and simplify operations in certain scenarios.

Here’s a breakdown of the pros and cons of using serviceaccount_name over serviceaccount_uid and how it impacts Vault’s cost optimization. Ref: alias_name_source

Why serviceaccount_name Reduces Costs

  1. Lowered Alias Churn:

    • Using serviceaccount_uid ties identity aliases to unique, system-generated UIDs. These UIDs change whenever a ServiceAccount is recreated, leading to the creation of new aliases in Vault.
    • Each alias incurs storage and operational overhead. Over time, environments with high churn (e.g., CI/CD pipelines or ephemeral workloads) can accumulate significant costs.

    Solution: Switching to serviceaccount_name binds the alias to the human-readable ServiceAccount name, which remains consistent even after recreation. This avoids unnecessary alias generation, reducing Vault’s storage usage and API calls.

  2. Simplified Policy Management:

    • With serviceaccount_name, policies can directly reference stable names, streamlining configuration.
    • This reduces the need for frequent policy updates caused by ServiceAccount UID changes, saving administrative effort and minimizing configuration drift.

  3. Optimized Performance:

    • Fewer aliases mean faster lookup times during authentication, reducing latency for applications and users.

Pros of serviceaccount_name

  • Cost Savings: Reduces storage and API request overhead by minimizing alias churn.
  • Predictability: Names are stable and human-readable, improving debugging and policy management.
  • Compatibility: Aligns better with environments leveraging long-lived ServiceAccounts.

Cons of serviceaccount_name

  • Risk of Name Collisions: If ServiceAccounts share the same name across namespaces, this can introduce conflicts. Ensure namespaces are considered in your configuration or choose unique naming conventions.
  • Less Granular Identity: UIDs are unique by design, while names might not fully represent individual resources. In environments where fine-grained identity is critical, serviceaccount_uid might still be preferable.

Best Practices for Implementation

  1. Evaluate Environment Needs:

    • Use serviceaccount_name for environments with frequent ServiceAccount recreation or high alias churn.
    • Stick with serviceaccount_uid for highly secure environments requiring strict uniqueness.

  2. Monitoring and Auditing:

    • Regularly audit identity aliases in Vault to identify and clean up unused entries, further optimizing costs.

Switching to serviceaccount_name is a practical choice for many use cases, particularly in cost-conscious or highly dynamic Kubernetes environments. However, ensure that your team understands its implications to balance simplicity, cost-efficiency, and security requirements.