Implement Switch & Rollback

Objective

Ensure traffic switch and rollback work reliably end-to-end. Mechanism depends on deployment style.

Path Selection

EKS Path

Verify make switch and make rollback delegate to infra repo. Create .github/workflows/rollback.yml with confirmation gate calling make rollback.

Elastic Beanstalk Path

Skill: AWS EB Blue/Green Deployment

1. Verify make swap

swap: ## Promote idle → prod
    bash scripts/promote-prod.sh

Test: deploy to idle → make swap → prod /health/ revision matches.

2. EB Rollback = Second Swap

No Helm rollback or Route53 weight change. The previously-live env still runs the old image:

# If prod is bad after swap:
make swap   # swaps back — old env becomes prod again

Document: rollback time ≈ CNAME swap + 90s DNS + smoke poll (~3 min max).

3. Create promote.yml (GitHub)

name: Promote to Production
on:
  workflow_dispatch:
    inputs:
      expected_revision:
        description: 'Release tag or EB VersionLabel (optional)'
        required: false
jobs:
  promote:
    environment: production   # approval gate
    steps:
      - run: bash scripts/promote-prod.sh
        env:
          EB_APP: {project}
          EB_ENV_A: {project}-prod
          EB_ENV_B: {project}-idle
          EXPECTED_REVISION: ${{ inputs.expected_revision }}
          MIMIR_PROD_URL: https://app.example.com

4. Optional Emergency Rollback Workflow

.github/workflows/rollback.yml — same as promote (another swap), with confirmation input type "rollback".

5. Runbook

Document in README:
- Promote: review idle URL → gh workflow run promote.yml or make swap
- Rollback: make swap again (no redeploy needed)
- When: smoke fails after promote, user reports, monitoring alerts

Deliverables

• ✅ Switch verified for chosen style
• ✅ EB: rollback documented as second CNAME swap
• ✅ promote.yml with production approval gate
• ✅ Optional rollback.yml with confirmation
• ✅ Runbook documented
• ✅ Rollback time measured (< 3 min for EB)