deployment nodejs (draft)

(if we cannot use hot-code reload and want 100% uptime)

1. split node instances in two groups, let's call them a and b
2. group a will be removed from nginx proxy pool
3. nginx reloads config
4. group a will be updated
5. group b will be removed from nginx proxy pool
6. group a will be added to the nginx proxy pool
7. nginx reloads config
8. group b will be updated
9. group b will be added to the nginx proxy pool
10. nginx reloads config
11. done