Design Patterns

Practice and make yourself familiar with GoFs design patterns. Some popular patterns in CloudStack:

Design Pattern	Usage in CloudStack
AbstractFactory and Factory	Several abstract classes and building blocks
Adapter	Resource and managers
Bridge	Frameworks and their provider plugins
Builder	Several building blocks
Command	RPC to talk to agents
Facade	Various subsystems
Observer and State	FSM and events
Decorator, Visitor and Flyweight	Network programming
Singleton	Managers and Providers instantiated as Spring beans
Strategy	Plugins, algorithms, Service Layers

Example Design Patterns implementations in Java:

Orchestration Patterns

Recommended reading list (from one of the original CloudStack architects):

Idempotent operations: https://cloudierthanthou.wordpress.com/2017/02/22/design-patterns-in-orchestrators-part-1/
Southbound APIs: https://cloudierthanthou.wordpress.com/2017/02/23/design-patterns-in-orchestrators-part-2/
Transfer of desired state: https://cloudierthanthou.wordpress.com/2017/06/22/design-patterns-in-orchestrators-transfer-of-desired-state-part-3n/
Network and firewall management:
- https://cloudierthanthou.wordpress.com/2015/04/09/how-to-manage-a-million-firewalls-part-1/
- https://cloudierthanthou.wordpress.com/2015/04/10/how-to-manage-a-million-firewalls-part-2/