⏪ 第14课：回滚策略

# 查看部署历史
kubectl rollout history deployment/myapp
# 查看特定版本详情
kubectl rollout history deployment/myapp --revision=3

# 回滚到上一版本
kubectl rollout undo deployment/myapp
# 回滚到指定版本
kubectl rollout undo deployment/myapp --to-revision=2
# 查看回滚状态
kubectl rollout status deployment/myapp

# 设置历史版本数量
kubectl patch deployment myapp -p '{{"spec":{{"revisionHistoryLimit":5}}}}'

# 紧急回滚脚本
cat > /usr/local/bin/k8s-rollback.sh << 'SCRIPT'
#!/bin/bash
set -euo pipefail
DEPLOY="${{1:?Usage: k8s-rollback  [ns] [rev]}}"
NS="${{2:-default}}"; REV="${{3:-}}"
echo "🚨 回滚 $DEPLOY..."
if [[ -n "$REV" ]]; then
    kubectl rollout undo deployment/"$DEPLOY" -n "$NS" --to-revision="$REV"
else
    kubectl rollout undo deployment/"$DEPLOY" -n "$NS"
fi
kubectl rollout status deployment/"$DEPLOY" -n "$NS" --timeout=120s
echo "✅ 回滚完成"
SCRIPT
chmod +x /usr/local/bin/k8s-rollback.sh

# 回滚最近一次提交（保留历史）
git revert HEAD && git push origin main

# 回滚指定提交
git revert abc1234 && git push origin main

# 回滚多个提交（逆序）
git revert HEAD~3..HEAD --no-commit
git commit -m "revert: rollback last 3 commits" && git push

# 基于Tag回滚
git tag -l 'v*' --sort=-v:refname | head -5
git checkout v2.0.0

# GitHub Actions自动回滚Workflow
cat > .github/workflows/auto-rollback.yml << 'EOF'
name: Auto Rollback on Failure
on:
  issues:
    types: [labeled]
jobs:
  rollback:
    if: contains(github.event.label.name, 'rollback')
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v4
      with: {{fetch-depth: 0}}
    - name: Get previous tag
      id: prev
      run: echo "tag=$(git tag -l 'v*' --sort=-v:refname | sed -n '2p')" >> $GITHUB_OUTPUT
    - name: Rollback
      run: |
        kubectl set image deployment/myapp myapp=myregistry/myapp:${{ steps.prev.outputs.tag }}
        kubectl rollout status deployment/myapp --timeout=300s
EOF

# Flyway undo迁移
cat > db/migration/U5__undo_add_phone.sql << 'EOF'
ALTER TABLE users DROP COLUMN IF EXISTS phone;
EOF
flyway undo -url="jdbc:postgresql://db:5432/mydb" -user=admin -password=secret

# Django迁移回滚
python manage.py migrate myapp 0004

# Rails迁移回滚
rails db:rollback STEP=3

# 最佳实践：Expand-Contract模式
# Step 1: Expand（加新列，兼容旧代码）
# ALTER TABLE users ADD COLUMN phone VARCHAR(20);
# Step 2: 切换应用代码到新版本
# Step 3: Contract（确认后删旧列）
# ALTER TABLE users DROP COLUMN old_phone;

# LaunchDarkly风格Flag
cat > feature-flags.yaml << 'EOF'
flags:
  new-checkout:
    enabled: false
    rules:
    - variation: true
      percentage: 5
EOF

# 应用中检查Flag(Python)
# if ld_client.variation("new-checkout", user, False):
#     return new_flow(request)
# return old_flow(request)

# 紧急关闭Feature（秒级回滚）
curl -X PATCH "https://app.launchdarkly.com/api/v2/flags/default/new-checkout" \
  -H "Authorization: " \
  -H "Content-Type: application/json" \
  -d '{{"on": false}}'

# Unleash（开源Feature Flag）管理
curl -X POST "http://unleash:4242/api/admin/features/new-checkout/toggle/off" \
  -H "Authorization: "