AIP 4110: How to retrieve tokens from the metadata server #1467
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wyuan1704
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Jan 6, 2025
wyuan1704
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Jan 6, 2025
aip/auth/4110.md
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| Instead, you should maintain an in-memory cache of the access token, and use the | ||
| cached token across all of your outbound requests. | ||
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| **Use a robust refresh strategy:** Each time you attempt to use the cached |
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Google Auth golang 0.6.0 (googleapis/google-cloud-go#10426) supports this non-blocking token refresh feature. If they can't use Google SDK for some reason, they can take it as an example for their implementation.
sai-sunder-s
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Jan 8, 2025
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Add a complete discussion of how auth libraries and workloads should cache and refresh tokens when loading them from the metadata server. Existing GCP auth libraries handle this properly, but occasionally it is not possible or desirable to use a preexisting auth library. This new section of the AIP provides guidance for those who need to directly retrieve tokens.
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@sai-sunder-s This is ready for another review pass |
| @@ -133,7 +144,7 @@ digraph d_front_back { | |||
| 1. If the credential is [an external account][8] JSON, go to step (4) | |||
| 1. If the credential is unknown type, return an error saying that _[END]_ | |||
| 1. Credentials not found _[END]_ | |||
| 1. **Check workload credentials (on GCE, GKE, GAE and Serverless)** | |||
| 1. **Check workload access token (on GCE, GKE, GAE and Serverless)** | |||
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One of the sub points talk about id token. So better to keep this as credentials?
| Request: `GET | ||
| http://169.254.169.254/computeMetadata/v1/instance/service-accounts/default/identity`. | ||
| Accepts the following query parameters: | ||
| * `audience` (Required): The audience for which this token should be issued. |
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we can ask for any audience?
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| **Use a robust refresh strategy:** Each time you attempt to use the cached | ||
| access token, check the remaining lifetime of the token. | ||
| * If it is greater than 225 seconds, the token is fresh. Proceed to use it. |
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what is the reasoning behind 225?
| Certain implementations of the metadata server use the "Background Refresh" | ||
| strategy described above for managing their own internal caches of tokens. For | ||
| example, when running on GKE with Workload Identity Federation for GKE enabled, | ||
| gke-metadata-server will not reliably return a refreshed access token until 120 |
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If we will get back stale token until 2 mins before expiry, why should we try refresh 225 secs before expiry?
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Add a complete discussion of how auth libraries and workloads should cache and refresh tokens when loading them from the metadata server.
Existing GCP auth libraries handle this properly, but occasionally it is not possible or desirable to use a preexisting auth library. This new section of the AIP provides guidance for those who need to directly retrieve tokens.