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Level 7 / Project 11 - Pipeline Feature Flags

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— This project — — Flashcards — —

Focus

  • runtime toggles for safe rollout

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-7/11-pipeline-feature-flags
python project.py --input data/sample_input.txt --output data/output_summary.json
pytest -q

Expected terminal output

... output_summary.json written ...
2 passed

Expected artifacts

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

Alter it (required)

  1. Add a time_window parameter so a flag is only active during specific hours (e.g. 09:00-17:00).
  2. Add a toggle() method that flips a flag's enabled state and records it in the audit log.
  3. Re-run script and tests — verify time-windowed flags and toggle work correctly.

Break it (required)

  1. Create a circular dependency (flag A requires B, flag B requires A) and observe infinite recursion.
  2. Set rollout_pct to a value above 100 or below 0.
  3. Capture the RecursionError or unexpected always-on behavior.

Fix it (required)

  1. Track visited flags during dependency resolution to detect and break circular references.
  2. Clamp rollout_pct to the 0-100 range in the Flag constructor.
  3. Add tests for circular dependencies and out-of-range rollout percentages.

Explain it (teach-back)

  1. Why are feature flags useful for deploying risky pipeline changes?
  2. What caused the infinite recursion with circular dependencies?
  3. How did the visited-set approach break the cycle?
  4. How do real feature flag systems (LaunchDarkly, Unleash) handle rollout percentages?

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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