This document discusses key considerations for architecting Azure solutions, including: - Software architecture focuses on the fundamental organization of a system, including its components, relationships, and design principles. - Idempotency is important to address problems like messages being processed multiple times if a worker role fails. Transaction IDs can be used to prevent duplicate processing. - Latency in Azure may be zero, but using bandwidth and other resources has real costs that must be accounted for in architecture. - Service Bus enables secure and reliable messaging across hybrid cloud/on-premises applications and networks.

1. Things to think about whilearchitecting Azure solutions

2. Famous Last Words… “It is a very humbling experience to make a multimillion-dollar mistake, but it is also very memorable….” (Fred Brooks - “Mythical Man-Month” p.47)

3. So, What is Software Architecture exactly?

4. Software architecture is the fundamentalorganization of a system, embodied in its components, their relationships to each other and the environment, and the principles governing its design and evolution

5. Architecture forces Stakeholders Quality Attributes Constraints Principles Community experience Architect Architecture Patterns & Anti-patterns Key people Technology A “deliverable” Produce Is an input

7. Dequeue/Delete pattern The Network is reliable

8. Dequeue/Delete pattern The Network is reliable Still a problem If we crash here

9. Idempotencyf(x) = f(f(x))

10. Messages Process At Least Once Debit bank account $100 message Worker role reads message Balance debited $100 Worker role is torn before message can be deleted 3 minutes later, message re-appears on queue Worker role reads message Balance debited $100 Message deleted from queue Chaos ensues..... Customer calls bank..... Web Role Worker Role Balance = $1000 Balance = $900 Balance = $800 Worker Role Web Role Worker Role Worker Role Queue Storage LB LB

11. Solving the Idempotency Problem Debit bank account $100 message with transaction ID Worker role reads message. Checks transaction ID not present. Writes transaction ID with state ‘Started’ to ‘Replay Log’ Balance debited $100 Worker role is torn before message can be deleted 3 minutes later, message re-appears on queue Worker role reads message. Checks transaction ID. It is present in state started. Compensating message written to another queue Message deleted from queue Compensatory message processed. Balance = $1000 Balance = $900 Web Role Worker Role Worker Role Web Role Storage Worker Role Worker Role Query Query Queue Queue Table LB LB

12. Latency is zero

13. It might be infinite for all purposes but it costs… Bandwidth is infinite

14. Authentication with ACS The Network is Secure Slide by Alik Levin

15. Service Bus Provides secure messaging and connectivity across different network topologies Enables hybrid applications that span on-premises and the cloud Enables various communication protocols and patterns for developers to engage in reliable messaging Topology doesn’t change

16. Enabling hybrid applications Datacenter Partner LOB app Mobile Device LOB web service

17. Enabling hybrid applications Datacenter Partner ACS LOB app SB Mobile Device LOB web service

18. Enabling hybrid applications Datacenter Partner ACS LOB app SB Mobile Device LOB web service

19. Enabling hybrid applications Partner Datacenter ACS LOB app SB Mobile Device LOB web service

20. Enabling hybrid applications Partner Datacenter ACS LOB app SB Mobile Device LOB web service

21. Electricity Power Grid Demo

22. Don’t assume specific instances Virtual IP : 1.1.1.2 Virtual IP : 1.1.1.3 Virtual IP : 1.1.1.4 Worker Role Worker Role Web Role Service Service IIS Instance Instance Windows Kernel Windows Kernel Windows Kernel TCP/IP TCP/IP TCP/IP TCP/IP TCP/IP NLB Driver NIC Driver NIC Driver NIC Driver Virtual NIC Virtual NIC Virtual NIC Virtual IP : 1.1.1.1

23. Inter-role communications

24. Reduced Headache on the one handNew challenges on the other There is one administrator

25. Azure MMC Snap-in http://code.msdn.microsoft.com/windowsazuremmc

26. Cerebrata – Azure Diagnostics Manager http://www.cerebrata.com/Products/AzureDiagnosticsManager/Default.aspx

27. Distribution cost in serialization, time on the wire, security Transport cost is zero

28. A lot of calls to fulfill a business function

29. Bring Data close to computation

30. It isn’t – but it’s abstractedunless of course you use Azure connect The Network is homogenous Quickly connect on-premise computers with the cloud, no networking configuration required Supports standard IP protocols; secured using end-to-end IPSec Integrated with the Windows Azure Service Model; all role types supported

31. Deployment view Consider xsmall instances for development Test if you can use less than medium for production

32. Cost considerations You pay when you’re deployed (there is no “shelving”) Shutdown doesn’t help (keep CPUs running..)

33. 2 Small instances cost the same as 1 medium instance

34. 2 instances can give you better availability Need to be on different fault and upgrade domains

35. I/O performance on smaller instances might be problematic

36. You can control Azure from scripts and code (even dev fabric) Testing

37. Demo Cloudoscope Acceptance Tests

38. Illustrations Slide 11 http://www.sxc.hu/photo/1201443 Slide http://www.sxc.hu/photo/1160486