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Level 8 / Project 10 - Dependency Timeout Matrix

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— This project — — Flashcards — —

Focus

  • Per-dependency timeout configuration with concurrent.futures
  • Matrix-style testing across multiple timeout values
  • Retry logic with configurable attempt counts
  • Health status classification: healthy, degraded, timeout, error
  • Optimal timeout analysis from matrix results

Why this project exists

Microservice systems depend on many external services — authentication, databases, caches, search indices, notification services — each with different latency profiles. Setting one global timeout (e.g. 30 seconds) is either too generous for fast services or too aggressive for slow ones. This project builds a dependency manager that tests per-service timeouts across a matrix of values, identifies the minimum viable timeout for each dependency, and recommends optimal settings — preventing the cascading failures that bring down entire distributed systems.

Run (copy/paste)

cd <repo-root>/projects/level-8/10-dependency-timeout-matrix
python project.py --demo
pytest -q

Expected terminal output

{
  "matrix": {"dependencies": [...], "matrix": [...]},
  "analysis": {"auth-service": {"min_passing_timeout": 0.05, ...}, ...}
}
7 passed

Expected artifacts

  • Console JSON output with timeout matrix and analysis
  • Passing tests
  • Updated notes.md

Alter it (required)

  1. Add a --parallel flag that checks all dependencies concurrently using ThreadPoolExecutor.
  2. Add exponential backoff to the retry logic (instead of fixed-interval retries).
  3. Add a criticality field to DependencyConfig and sort the matrix output by it.

Break it (required)

  1. Set timeout_seconds=0 for a dependency — does the check handle instant timeouts?
  2. Configure a dependency with max_retries=-1 — does it retry forever?
  3. Pass a health_check function that hangs indefinitely — does the timeout work?

Fix it (required)

  1. Validate that timeout_seconds > 0 and max_retries >= 0 in DependencyConfig.
  2. Add a hard upper limit on retries to prevent infinite loops.
  3. Add a test for the exponential backoff behavior.

Explain it (teach-back)

  1. Why do microservices need explicit timeout configuration for each dependency?
  2. How does ThreadPoolExecutor enable concurrent timeout checks?
  3. What is the difference between a connection timeout and a read timeout?
  4. Why is a timeout matrix critical for understanding cascading failures?

Mastery check

You can move on when you can: - explain why every network call needs a timeout (and what happens without one), - describe cascading failures and how timeouts prevent them, - add a new dependency with custom health check and timeout without looking at docs, - explain retry strategies: fixed, linear, exponential backoff, and jitter.

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