Retry transient reads and reuse completed requests

Stage 3 of 4. Read the project prerequisites before starting; this stage builds on the preceding contracts.

What changes

Retry only transient timeout failures and cache successful reads by a canonical action identity. A permission failure is not transient and must escape immediately. This cache is request-local: real cloud state changes, so a long-lived cache needs an explicit TTL or version instead of silently reusing old data.

Work through one concrete case

The plan reads checkout metrics twice. The first call times out once and then succeeds; the second logical read reuses the cached value. Provider calls=2, completed logical reads=2, cache hits=1.

Change the lab inputs and calculate the result before reading its metrics. The figure computes from those inputs; the implementation tests below remain the source of completion evidence.

Implement the contract

Implement retry.py: request_key, cached_read. This artifact is stage 3 of Cloud Agent With AWS Strands. It consumes explicit inputs and returns an inspectable result that the next stage can use.

Use the public API contract and the typed starter signatures. Return values from core functions and let the supplied driver own file input, argument parsing and presentation.

Cache only successful results under a canonical pair of operation and resource. Permission errors bypass the timeout retry loop; repeating them cannot grant authority.

Verify and inspect

From the repository root, initialize once with python3 scripts/project_test.py cloud-agent-with-aws-strands --init learning-artifacts/cloud-agent-with-aws-strands. Then grade cumulatively:

python3 scripts/project_test.py cloud-agent-with-aws-strands --stage 3 --path learning-artifacts/cloud-agent-with-aws-strands --strict

A fresh workspace should fail until you implement the contract. After every stage is complete, run your actual artifact from the supplied sample:

cd learning-artifacts/cloud-agent-with-aws-strands
python3 cli.py samples/input.json --output incident.json

Investigate the failure boundary

Change the second resource to another scoped service. It must produce a different cache key even though the operation is identical.

References

Reference 1