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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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