[coughlmao]

Issue number: closes #8727

Summary

Fix a race condition in the Redis idempotency persistence layer where an existing record expires between a failed SET NX operation and the subsequent GET.

Previously, this caused an IdempotencyItemNotFoundError to escape and be wrapped as an IdempotencyPersistenceLayerError, failing the Lambda invocation instead of retrying.

Changes

• Catch IdempotencyItemNotFoundError when retrieving a record after a failed Redis SET NX.
• Raise IdempotencyInconsistentStateError to signal the recoverable inconsistent state.
• Ensure the existing idempotency retry mechanism can retry the operation.
• Add regression tests covering the disappearing-record race condition, exception chaining, and successful retry through the public idempotency decorator.

User experience

Before: If an existing Redis idempotency record expired between SET NX and GET, the invocation failed with a persistence-layer error.

After: The Redis persistence layer raises IdempotencyInconsistentStateError, allowing the existing retry mechanism to retry the operation. The invocation succeeds when the subsequent attempt acquires the lock successfully.

Verification

Tests and checks run locally:

• uv run --locked pytest tests/functional/idempotency/_redis/test_redis_layer.py -k inconsistent_state -v — 3 passed.
• uv run --locked pytest tests/functional/idempotency/_redis/test_redis_layer.py -q — 33 passed.
• Idempotency functional tests — 203 passed.
• uv run --locked ruff check aws_lambda_powertools/utilities/idempotency/base.py aws_lambda_powertools/utilities/idempotency/persistence/redis.py tests/functional/idempotency/_redis/test_redis_layer.py — passed.
• uv run --locked mypy aws_lambda_powertools/utilities/idempotency/base.py aws_lambda_powertools/utilities/idempotency/persistence/redis.py — passed.
• git diff --check — passed.
• Git pre-commit hooks — all passed.

The regression scenario was verified using a mocked Redis client. Real Redis service validation has not been performed.

This contribution was developed with AI assistance. I reviewed the changes and personally ran the tests and checks listed above.

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[boring-cyborg]

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[leandrodamascena]

Thanks for the PR and for filling in the verification section, that helps. Heads up that the review may take a few days: this goes into 3.41.0 and I review every PR against a real service before approving, one at a time. No need to rebase or ping in the meantime, I'll come back here.