GitHub Actions: From Zero to Production(EP9)🚀

Episode 9 – Debugging & Troubleshooting GitHub Actions

If you’ve written a few GitHub Actions workflows, you’ve probably faced this situation:

❌ The workflow failed
❓ The error message makes no sense
😕 Re-running sometimes “fixes” it

This episode is about debugging GitHub Actions effectively — the skill that separates someone who knows the syntax from someone who can operate CI/CD in real projects.

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Why Debugging Matters

CI/CD pipelines:

• run on remote machines
• use ephemeral environments
• rely on permissions and secrets
• fail silently sometimes

That means:

Debugging is not optional — it’s a core skill.

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1️⃣ How to Read GitHub Actions Logs Properly

When a workflow fails, always follow this order:

Actions tab
 → Workflow run
   → Job
     → Step

What to focus on:

• ❗ The first error, not the last line
• ❌ Exit codes (exit 1, command failed)
• 🧱 Which step failed (step names matter!)
• ⏱️ Sudden slow steps (performance issues)

👉 Always name your steps clearly:

- name: Install dependencies
  run: npm ci

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2️⃣ Most Common Failure Patterns (Real World)

❌ Missing code

package.json not found

Cause:

• actions/checkout missing

Fix:

- uses: actions/checkout@v4

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❌ Dependency failures

Cannot find module

Causes:

• wrong Node version
• npm install instead of npm ci
• broken lockfile

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❌ Secrets not available

API_KEY is undefined

Causes:

• forked PR
• wrong secret name
• missing environment

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❌ Permission errors

403 Resource not accessible by integration

Causes:

• missing permissions
• read-only GITHUB_TOKEN
• restricted fork context

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3️⃣ Debugging with Logs (Safely)

Print environment details

- run: |
    echo "Branch: $GITHUB_REF"
    echo "Actor: $GITHUB_ACTOR"

Print GitHub context (very useful)

- run: echo "${{ toJson(github) }}"

This helps you understand:

• which event triggered the workflow
• branch vs PR context
• actor permissions

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4️⃣ Enable Debug Mode (Powerful Feature)

GitHub supports debug logging via secrets.

Add repository secrets:

ACTIONS_STEP_DEBUG = true
ACTIONS_RUNNER_DEBUG = true

What you get:

• condition evaluations
• cache hit/miss logs
• detailed action internals

⚠️ Remove after debugging — logs become noisy.

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5️⃣ Reruns: Use Them Correctly

GitHub allows:

• Re-run all jobs
• Re-run failed jobs

Reruns are useful for:

• flaky network issues
• temporary outages
• transient errors

❗ If reruns “fix” issues often, your pipeline is not deterministic.

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6️⃣ Debugging if: Conditions

Steps silently skip if conditions fail.

Example:

if: github.ref == 'refs/heads/main'

Debug it:

- run: echo "Ref is $GITHUB_REF"

Common mistake:

main ≠ refs/heads/main

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7️⃣ Debugging Secrets Safely

Never print secret values.

Instead, check presence:

- run: echo "Secret exists: ${{ secrets.API_KEY != '' }}"

Checklist:

• correct secret name
• correct scope (repo vs environment)
• environment specified
• not a fork PR

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8️⃣ Debugging Matrix Jobs

Matrix jobs fail independently.

Example job name:

test (ubuntu-latest, node 20)

Tips:

• check which combination failed
• reduce matrix size when debugging
• disable fail-fast temporarily

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9️⃣ Senior-Level Debugging Habits ⭐

✅ Small, focused steps
✅ One responsibility per step
✅ Explicit permissions
✅ Log context early
✅ Avoid long inline scripts
✅ Fail fast, not silently

Boring pipelines are good pipelines.

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Final Mental Model (Lock This In)

Failure
  → Identify step
    → Identify cause
      → Fix root problem (not symptoms)

If you follow this flow, debugging becomes predictable.

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What’s Next?

👉 Episode 10 (Final):
Production CI/CD for Frontend Apps (GitHub Pages, React & Vite)

We’ll bring everything together:

• clean CI
• protected CD
• real deployment patterns

This final episode turns knowledge into production-ready confidence 🚀

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Thanks for reading!
Debug with confidence 👋