[Bug] Managed Identity should respect source when retrying request, IMDS has more codes should retry

[4gust]

Library version used

4.66.0

.NET version

.NET 9

Scenario

ManagedIdentityClient - managed identity

Is this a new or an existing app?

This is a new app or experiment

Issue description and reproduction steps

For MI The application only retries on
404 or 408 or 429 or 500 or 503 or 504 these codes
but for IMDS only you need to try on more codes. More information here
https://learn.microsoft.com/en-gb/entra/identity/managed-identities-azure-resources/how-to-use-vm-token#error-handling

Relevant code snippets

No response

Expected behavior

No response

Identity provider

Other

Regression

No response

Solution and workarounds

No response

[gladjohn]

Need to work with MSI team to finalize on this one.

HTTP Status Code	Error Reason	Recommended Action	Retry Delay Strategy
404	IMDS endpoint is updating	Retry with Exponential Backoff	1s → 2s → 4s → 8s
410	IMDS is going through updates	Wait up to 70 seconds, then retry	70s (fixed wait)
429	IMDS Throttle limit reached	Retry with Exponential Backoff	2s → 4s → 8s → 16s
408	Request Timeout	Retry with Exponential Backoff	1s → 2s → 4s → 8s
5xx	Transient service error	Retry with Exponential Backoff	1s → 2s → 4s → 8s
400	Bad Request (Invalid Parameters)	Do not retry, fix request	No retry
401	Unauthorized	Do not retry, check authentication setup	No retry
403	Forbidden	Do not retry, verify permissions	No retry
timeout	IMDS endpoint is updating	Retry with Exponential Backoff	1s → 2s → 4s → 8s

Retry Strategy (Exponential Backoff)

Retry Attempt	Delay Before Retry
1st	1 second
2nd	2 seconds
3rd	4 seconds
4th	8 seconds
5th	16 seconds (if applicable)

Notes:

• For 410 (IMDS Updates): No retries within 70 seconds. Directly wait for IMDS to be available.
• For 5xx Errors: Retry max 3 times before failing.
• For 429 (Throttling): Increase backoff delay on each retry.

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[Robbie-Microsoft]

@gladjohn can you order that table in ascending order for http status code? Additionally, what is the last item "timeout"? 408 (request timeout) or 504 (gateway timeout)? Can we be more specific for that item?

Additionally, can we keep all exponential backoffs to the same values? Why does 429 need to start at 2 seconds instead of 1?

[gladjohn]

@gladjohn can you order that table in ascending order for http status code? Additionally, what is the last item "timeout"? 408 (request timeout) or 504 (gateway timeout)? Can we be more specific for that item?

Additionally, can we keep all exponential backoffs to the same values? Why does 429 need to start at 2 seconds instead of 1?

This is not the final @Robbie-Microsoft, this is just a starting point and needs review by MSI team.