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Level 5 / Project 10 - API Polling Simulator

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— This project — — Flashcards — Browser

Quick Recall: This project uses rule-based scoring to decide when to retry or back off. Before starting, make sure you can: write a function that evaluates multiple conditions and returns a score or category based on thresholds (Level 1, Project 02 - Password Strength Checker).

Estimated time: 80 minutes

Focus

  • poll cycles, retries, and delays

Why this project exists

This project gives you level-appropriate practice in a realistic operations context. Goal: run the baseline, alter behavior, break one assumption, recover safely, and explain the fix.

Run (copy/paste)

Use <repo-root> as the folder containing this repository's README.md.

cd <repo-root>/projects/level-5/10-api-polling-simulator
python project.py --max-polls 10 --output data/poll_results.json
pytest -q

Expected terminal output

Polling complete: 10 attempts, 7 successful, 2 rate-limited
6 passed

Expected artifacts

  • data/poll_results.json
  • Passing tests
  • Updated notes.md

Checkpoint: Baseline code runs and all tests pass. Commit your work before continuing.

Alter it (required) — Extension

  1. Add a --timeout flag that stops polling after N seconds regardless of max polls.
  2. Track and report the average response time per successful poll.
  3. Add a --fail-rate parameter to control the MockAPI's simulated failure percentage.
  4. Re-run script and tests.

Break it (required) — Core

  1. Set --max-polls 0 and observe the behavior.
  2. Configure the MockAPI to always return rate-limit errors and watch backoff grow indefinitely.
  3. Capture the first failing test or visible bad output.

Fix it (required) — Core

  1. Validate that max_polls is at least 1.
  2. Cap the maximum backoff delay so it does not grow unbounded.
  3. Add tests for zero-polls and capped backoff.
  4. Re-run until output and tests are deterministic.

Checkpoint: All modifications done, tests still pass. Good time to review your changes.

Explain it (teach-back)

  1. How does poll_with_backoff increase the delay after each rate-limit response?
  2. What is the purpose of the MockAPI class in testing?
  3. Why is exponential backoff better than fixed-interval polling?
  4. Where do you see polling with backoff in production (AWS SDK, GitHub API, payment webhooks)?

Mastery check

You can move on when you can: - run baseline without docs, - explain one core function line-by-line, - break and recover in one session, - keep tests passing after your change.

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