Giới thiệu
Hầu hết hệ thống thực tế bắt đầu từ Monolith — và monolith tốt! Migration sang Microservices + Micro Frontend là quá trình dài, không phải big bang rewrite. Bài này hướng dẫn lộ trình migration an toàn, từng bước.
1. Strangler Fig Pattern
1.1 Ý tưởng
Strangler Fig Tree: cây phụ bao quanh cây chủ,
dần dần thay thế cho đến khi cây chủ biến mất.
Phase 1: Monolith xử lý mọi thứ
┌──────────────────────┐
│ Monolith │
│ Users│Products│Orders│
└──────────────────────┘
Phase 2: Extract service, route traffic
┌───────────────────────┐
│ API Gateway │
├───────────┬───────────┤
│ Monolith │ Product │
│ (Users, │ Service │
│ Orders) │ (new) │
└───────────┴───────────┘
Phase 3: Extract more services
┌───────────────────────────┐
│ API Gateway │
├────────┬────────┬─────────┤
│Monolith│Product │ Order │
│(Users) │Service │ Service │
│ │ │ (new) │
└────────┴────────┴─────────┘
Phase N: Monolith is gone
┌────────────────────────────────┐
│ API Gateway │
├────────┬────────┬──────────────┤
│ User │Product │ Order │
│Service │Service │ Service │
└────────┴────────┴──────────────┘
2. Migration Assessment
2.1 Phân tích Monolith
Trước khi migration, hiểu monolith:
Code Analysis:
├── Module coupling (which modules call which?)
├── Database coupling (shared tables?)
├── Hot spots (most changed code)
├── Complexity (cyclomatic, LOC)
└── Team ownership (ai maintain gì?)
Prioritization Matrix:
┌──────────────────────────────────────┐
│ Business Value │
│ High │ ★ Extract first │ Rewrite │
│ │ (Product, │ later │
│ │ Order) │ │
│──────┼─────────────────┼────────────│
│ Low │ Leave in │ Consider │
│ │ monolith │ removing │
│ │ (low ROI) │ │
│ └──── Low ─────── High ────────│
│ Change Frequency │
└──────────────────────────────────────┘
3. Backend Migration Playbook
3.1 Phase 1: API Gateway (Week 1-4)
1. Deploy API Gateway trước monolith
2. Route ALL traffic qua Gateway
3. Gateway forward mọi thứ đến Monolith
4. Không thay đổi behavior — chỉ thêm routing layer
Frontend → API Gateway → Monolith (no change)
3.2 Phase 2: Extract First Service (Week 5-12)
Chọn service ít coupling nhất (ví dụ: Product Catalog)
Steps:
1. Create Product Service (new codebase)
2. Copy/rewrite product logic
3. Setup database (copy product tables)
4. Dual-write: monolith write cả old DB + new service
5. Verify data consistency
6. Switch reads: Gateway route GET /products → new service
7. Switch writes: Gateway route POST/PUT /products → new service
8. Remove product code from monolith
9. Drop product tables from monolith DB (after verification)
3.3 Data Migration Strategy
Dual-Write Pattern:
Phase A: Monolith writes to Old DB + New DB
Reads from Old DB
→ Verify New DB data matches
Phase B: Monolith writes to Old DB + New DB
Reads from New DB (switch)
→ Verify reads correct
Phase C: New Service writes to New DB only
Monolith no longer involved
→ Clean up Old DB tables
4. Frontend Migration Playbook
4.1 Phase 1: Shell App (Week 1-4)
1. Create Shell App (new React app)
2. Shell wraps existing monolith frontend (iframe initially)
3. Shell provides Header, Footer, Navigation
4. Gradually replace iframe sections with MFEs
4.2 Phase 2: Extract First MFE (Week 5-8)
Extract Product pages as first MFE:
1. Create product-mfe project
2. Configure Module Federation (expose ProductList, ProductDetail)
3. Shell loads product-mfe via Module Federation
4. Remove product pages from monolith frontend
5. Verify routing, styling, functionality
Shell App
├── Header (Shell)
├── /products/* → Product MFE (new, Module Federation)
├── /cart/* → Monolith Frontend (iframe, temporary)
├── /orders/* → Monolith Frontend (iframe, temporary)
└── Footer (Shell)
4.3 Gradual Replacement
Month 1: Shell + Product MFE
Month 2: + Cart MFE
Month 3: + Order MFE
Month 4: + Account MFE
Month 5: Remove iframe, monolith frontend retired
5. Migration Anti-patterns
❌ Big Bang Rewrite
→ 12-18 months later: "it's not ready yet"
→ Business can't wait, original monolith diverges
❌ Extract based on technical layers
→ "API service", "DB service", "Auth service"
→ Should be business domains: Product, Order, User
❌ Shared database between old and new
→ Defeats the purpose of database per service
→ Temporal coupling, schema changes break both
❌ Migration without observability
→ Can't compare old vs new behavior
→ Can't detect regressions
6. Migration Timeline (Typical)
E-Commerce Monolith → Microservices + MFE:
Month 1-2: Infrastructure setup
(K8s, CI/CD, monitoring, API Gateway)
Month 3-4: First service extraction
(Product Service + Product MFE)
Month 5-6: Second service extraction
(Order Service + Order MFE)
Month 7-8: Third + Fourth services
(Cart, User)
Month 9-10: Supporting services
(Payment, Notification, Inventory)
Month 11-12: Cleanup monolith
Remove old code, drop old tables
Ongoing: Optimize, add services as needed
7. Success Metrics
| Metric | Before (Monolith) | After (Micro*) |
|---|---|---|
| Deploy frequency | 1/week | 5-10/day per team |
| Lead time | 2 weeks | 1-2 days |
| MTTR | 2-4 hours | 15-30 min |
| Change failure rate | 15% | < 5% |
| Team autonomy | Low (PR conflicts) | High (independent) |
| Build time | 15 min | 2-3 min (per service) |
Tóm tắt
- Strangler Fig Pattern: migrate gradually, not big bang rewrite
- Extract by business domain, not technical layer
- Dual-write for data migration safety
- API Gateway first → route traffic incrementally
- Frontend: Shell App → extract MFEs one by one
- Timeline: 9-12 months for typical e-commerce
- Measure success: deploy frequency, lead time, MTTR
🎉 Chúc mừng hoàn thành Series!
Bạn đã đi qua toàn bộ hành trình:
- Nền tảng: Monolith → Microservices → Micro Frontend evolution
- Backend: Service decomposition, API design, async communication
- Data: Database per service, Saga, Event Sourcing
- Frontend: Micro Frontend architecture, Module Federation, Shell App
- Integration: BFF, API Gateway, GraphQL Federation
- Quality: Testing strategy, Contract Testing
- Deployment: CI/CD, Canary, GitOps
- Production: Observability, Performance, Security
- Practice: Case Study, Migration Guide
Tiếp theo: Áp dụng vào dự án thực tế! Bắt đầu nhỏ, validate sớm, iterate nhanh.