Lift & Shift, Cut Overs, and other Bad Habits

The last time you moved, you had that box. You haven’t opened it in years. You still haven’t opened it but you carry it around with you like a treasured keepsake. Unfortunately, we moved to the cloud the same way. We brought all of our habits, practices, and patterns without considering which may be strengths or weaknesses.

In this session, we’ll skip the tools and take a look at our new constraints and capabilities the cloud gives us. Through this, we’ll explore three architectural Cloud Design Patterns - Circuit Breaker, the Strangler, and Pub/Sub - to make our systems more reliable, more maintainable, and probably cheaper to run.

Transcript

1. Lift & Shift, Cut Overs, and other Bad Habits Product Manager keith.casey@pangea.cloud
2. Agenda - Intro - What are Design Patterns? - Rethinking for the Cloud - Strangler - Publisher/Subscriber - Circuit Breaker - Next Steps
3. Who am I?
4. Who am I?
5. Who am I?
6. What are Design Patterns?
7. 7 7 7 A way to express a complex solution to a problem in a simple, repeatable way We do this in many areas - Goldilocks - Catch 22 - Kobayashi Maru What is a Design Pattern?
8. 8 8 8 What are some familiar ones?
9. Types of Design Patterns Creational Structural Behavioral Scope Class Factory Adapter Interpreter Object Abstract Factory Adapter Chain of Responsibility Builder Bridge Command Prototype Composite Iterator Singleton Decorator Mediator Facade Observer Flyweight Strategy Proxy Visitor
10. 10 10 10 The Old World - Direct access to systems - 3-tier architecture (presentation, app, data) - Simple request/response - Local request/response - Potentially single server - Predictable components & configurations - Complete control over the stack The New(ish) World - DevOps and Build pipelines - Microservices - Distributed systems - Ephemeral systems - Scalable, unpredictable architecture - Predictable configurations - Minimal control for developers Why they break down
11. Our Approaches
12. Lift & Shift: What we Think
13. Lift & Shift: Reality
14. Lift & Shift: Reality
15. Cut Overs: What we Think
16. Cut Overs: Reality
17. Other Ideas - Hybrid: What we Think
18. Other Ideas - Hybrid: Reality
19. Rethinking for the Cloud
20. 20 20 20 - Microservices - Distributed Logging - Federated Identity - Load Balancing - Promises - Service Discovery - Service Mesh - Sidecars - Mock Objects - Work Objects What’s out of bounds this time?
21. Disclaimer: These are descriptive, not prescriptive.
22. 22 22 22 “If you know the problem and know yourself, you need not fear the result of a hundred releases. If you know yourself but not the problem, for every release you will also suffer downtime. If you know neither the problem nor yourself, you will break everything and have no flippin’ clue why.” ~ Sun Tzu Some Wisdom
23. The Strangler
24. What problem do we have? We have an old system We want to have a new system The old system has to keep working
25. What does this pattern do? Old System Facade Old System Old System Old Facade New Old Facade New New System Facade
26. When do we use it? The old system has to keep working We want to separate/isolate components Great for testing high risk components Ref: https://martinfowler.com/bliki/StranglerFigApplication.html
27. Do you have a single point of entry/control? Now you have to maintain the facade too! Can the facade keep up with the changes? Is the facade a single point of failure? Can both systems handle data jointly? What are the tradeoffs?
28. Blue/Green Deployments Highway Bypasses What does it look like in the wild?
29. Publisher/ Subscriber
30. We have distributed components that need to interact We may not have a list of every listener Not every listener cares about every message What problem do we have?
31. What does this pattern do? Ref: https://learn.microsoft.com/en-us/azure/architecture/patterns/publisher-subscriber
32. When do we use it? We have distributed, event-driven systems We don’t have control over the endpoints We have varied architectures, languages, etc Our listeners are scaling quickly or are ephemeral
33. What are the tradeoffs? Security - there are many ways to screw this up This is a broadcast-only, not bi-directional Messages will be received out of order Messages can be lost or repeated Can you replay messages?
34. What does it look like in the wild? Webhooks!* Airports
35. Circuit Breaker
36. What problem do we have? Things break! Things come back! We have to protect our app and users
37. Protects the system but cutting off - or breaking - connectivity to other systems Optionally: Provide a fallback option Optionally: Monitor the underlying system and recover automatically once it’s restored What does this pattern do? Ref: https://martinfowler.com/bliki/CircuitBreaker.html
38. Any time we want to isolate a dependency/subsystem AND Our system can be “useful enough” without the subsystem When do we use it?
39. Ref: https://aws.amazon.com/blogs/compute/using-the-circuit-breaker-pattern-with-aws-step-functions-and-amazon-dynamodb/ What are the tradeoffs? How do we handle the exceptions? How do we trigger a reset/recovery? How do we test success, failure, and the transition states? Some things should knock our systems offline
40. What does it look like in the wild? Circuit breakers Traffic reports
41. Wrap Up
42. - Design Patterns - complex ideas in simple repeatable explanations - Rethinking for the Cloud - our constraints have changed - Strangler - replace an old system safely over time - Publisher/Subscriber - communicate between distributed systems - Circuit Breaker - protect your system & recover from failures Recap
43. 43 43 43 Pulling these together CB old system facade client new system monitoring
44. 44 44 44 - Microservices - Distributed Logging - Federated Identity - Load Balancing - Promises - Service Discovery - Service Mesh - Sidecars - Mock Objects - Work Objects Other Cloud Design Patterns
45. 45 45 45 Where can I learn more? - Martin Fowler’s Patterns of Legacy Displacement - Microsoft’s Azure Architecture Center - PHP: Design Patterns on LinkedIn - webhooks.fyi - In progress: DesignPatterns.fyi
46. Lift & Shift, Cut Overs, and other Bad Habits Product Manager keith.casey@pangea.cloud