.NET Developer Days 2015, PL: Defensive programming, resilience patterns & antifragility
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Cloud computing, DevOps, IOT or just connecting the local active directory or {put any LOB system here}: The applications we build are getting more and more distributed. Now guess who's guilty if your application fails, because there was some error outside of your code (even outside of your control influence)? This session is about designing, developing and deploying rock solid applications.
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.NET Developer Days 2015, PL: Defensive programming, resilience patterns & antifragility
- 1. danielfisher.com Defensive Programming, Daniel Fisher Resilience Patterns & Antifragility
- 2. danielfisher.com I’m a technician & always concerned about bandwidth So I ask you to send one packet instead of two DANIEL My name is Any further questions? Just Ask!
- 3. danielfisher.com software I design, develop, deploy, teach, train, coach and speak HTML5 & WEB, DATA ACCESS & PERFORMANCE, SCALABLE & TESTABLE DESIGN, DISTRIBUTED SYSTEMS & SERVICES, SECURITY & TRUST lennybacon.com my blog url @lennybacon my twitter handle info@danielfisher.com my smtp find my services at danielfisher.com
- 4. danielfisher.com THAT IS ALL THAT I DEEPLY BELEVE IN D I S C L A I M E R IT FITS MY SHOES IT MIGHT NOT FIT YOURS THIS PRESENTATION CONTAINS MY PERSONAL VIEW ON THE WORLD IT IS BASED ON MY EXPERIENCE IN SOFTWARE DEVELOPMENT PROJECTS SINCE 1996 MOST THINGS I LEARNED FROM PAIN OTHERS FROM MOMENTS OF GRACEFULNESS, BRAVENESS & SUCCESS
- 5. danielfisher.com CHAPTER 1 Software Development: A world of fear
- 8. danielfisher.com http://www.city-data.com/forum/anchorage/692696-anchorage-here-we-come-finally.html
- 10. danielfisher.com “Office Space” by Mike Judge / Twentieth Century Fox Film Corporation
- 16. danielfisher.com
- 19. danielfisher.com I have not failed! I've just found 10,000 ways that won't work …Thomas Edison
- 20. danielfisher.com CHAPTER 2 Paranoia basics: Defensive programming
- 22. danielfisher.com Yoda Conditions if (variable.Equals("literal")) { ... } if ("literal".Equals(variable)) { ... }
- 23. danielfisher.com Check Collections for Null var files = SomeApi.GetFileList(); if (files != null) { for (var i = 0; i < files.length; i++) { ... } }
- 24. danielfisher.com All classes are sealed by default public class Class1 { ... } internal sealed class Class1 { ... }
- 25. danielfisher.com DDD Value Object Input Validation public sealed class ZipCode : IValueObject { public ZipCode(int value) { // Input validation!!! Value = value; } public int Value { get; private set;} }
- 26. danielfisher.com CHAPTER 3 Advanced paranoia tactics: Robustness
- 28. danielfisher.com Finding Bugs is good and mustn’t be punished! It makes code less buggy!
- 29. danielfisher.com Finding Bugs in tests is even better! No customer will even face them!
- 30. danielfisher.com Try to break, burn, shoot and drown it together! I call it Breakstorming!
- 31. danielfisher.com CHAPTER 4 Professional Paranoia: Resilience patterns
- 32. danielfisher.com A distributed system is one in which the failure of a computer you didn't even know existed can render your computer unusable http://research.microsoft.com/en-us/um/people/lamport/pubs/distributed-system.txt
- 33. danielfisher.com
- 34. danielfisher.com Topology changes Networks fail Latency varies by location Bandwidth differs by location Things get hacked
- 35. danielfisher.com Servers get rebooted Code has bugs Other users might use it different Failover means offline Processing time varies by amount of data Environments differ File system is not always available
- 36. danielfisher.com Life is not a walk in the park. neither is software!
- 37. danielfisher.com Success is the ability to go from one failure to another with no loss of enthusiasm. WinstonChurchill
- 38. danielfisher.com Scale like a boss Asynchronicity No one waiting for an error Bulkheads & Replays Loose coupling for the win But dare you forget the dead letters No cascading failures and stack trace
- 39. danielfisher.com BASE OVER ACID Atomic, Consistent, Isolated and Durable solutions are not a silver bullet. Basic Availability, Soft-state and Eventual consistency work better in most distributed scenarios. BUT YOU MUST THINK DIFFERENT FOR BASE Use a more relaxed consistency model to reduce coupling Queues are as transactional as databases
- 40. danielfisher.com Idempotency Non-idempotency is complicated to handle and increases coupling between participants. stateless stateless stateless THIS ALSO REQUIRES YOU TO THINK DIFFERENT But in the end it is nothing more than divide and conquer with an eye on the results Functional programming and immutable types for the win.
- 41. danielfisher.com Monitor & Audit Measure to gain latency control and detect non- timely responses before they time out. Learn more about the life of your system to predict its behavior. If you can’t debug, log is your friend Respond to detected failures. 20% - 40% logging code Auditing and Logging can even be party of your architecture
- 45. danielfisher.com CompensatingTransaction Pattern https://www.flickr.com/photos/susivinh/16341538221
- 46. danielfisher.com CHAPTER 5 Things that gain from disorder: Antifragility
- 47. danielfisher.com Nassim Nicholas Taleb wrote two interesting books about how economical systems behave. He focusses on what happens under stress and on unexpected occurrences of events. The black swan Antifragility
- 49. danielfisher.com What Doesn't Kill You Makes You Stronger Every time something catastrophic happens that you take on and survive… … your team and you code becomes Stronger, Better, Faster, More
- 50. danielfisher.com Asymmetric information & options An opportunity to cope with the lack of knowledge ST R AT E GY Business, Architecture & Code Long Term vs Short Term Sustainability vs Reward
- 51. danielfisher.com Thank you! danielfisher.com my company lennybacon.com my blog url @lennybacon my twitter handle info@danielfisher.com my smtp
Editor's Notes
- No NullReferenceException No accidential assignment
- No duplicate validation Trust that values are correct
- https://msdn.microsoft.com/en-us/library/dn589788.aspx
- https://msdn.microsoft.com/en-us/library/dn589784.aspx
- https://msdn.microsoft.com/en-us/library/dn568104.aspx
- https://msdn.microsoft.com/en-us/library/dn589804.aspx
- Thales of Milet and the olive press