The Walking Dead - A Survival Guide to Resilient Reactive Applications

This talk was given at Lambda Days Krakow 2015, a great event with focus on functional and reactive programming.

The slides are very much like the one given at Voxxed, but with a greater focus on functional and event driven paradigms.

Transcript

1. The Walking Dead A Survival Guide to Resilient Reactive Applications Michael Nitschinger @daschl
2. the right Mindset 2
3. – U.S. Marine Corps “The more you sweat in peace, the less you bleed in war.” 3
6. Not so fast, mister fancy tests! 6
7. What can go wrong? Always ask yourself 7
8. Fault Tolerance 101 8
9. Fault Error Failure A fault is a latent defect that can cause an error when activated. 9
10. Fault Error Failure Errors are the manifestations of faults. 10
11. Fault Error Failure Failure occurs when the service no longer complies with its specifications. 11
12. Fault Error Failure Errors are inevitable. We need to detect, recover and mitigate them before they become failures. 12
13. Reliability is the probability that a system will perform failure free for a given amount of time. MTTF Mean Time To Failure MTTR Mean Time To Repair 13
14. Availability is the percentage of time the system is able to perform its function. availability = MTTF MTTF + MTTR 14
15. Expression Downtime/Year Three 9s 99.9% 525.6 min Four 9s 99.99% 52.56 min Four 9s and a 5 99.995% 26.28 min Five 9s 99.999% 5.256 min Six 9s 99.9999% 0.5256 min 100% 0 15
16. Pop Quiz! Edge Service User Service Session Store Data Warehouse Wanted: 99.99% Availability ??? ??? ??? 16
17. Pop Quiz! Edge Service User Service Session Store Data Warehouse Wanted: 99.99% Availability 99.99% 17 99.99% 99.99%
18. Pop Quiz! Edge Service User Service Session Store Data Warehouse Wanted: 99.99% Availability ~99.999% ~99.999% ~99.999% 18
19. Fault Tolerant Architecture 19
20. Units of Mitigation are the basic units of error containment and recovery. 20
21. Escalation is used when recovery or mitigation is not possible inside the unit. 21
22. Escalation 22 Cluster Node Node Service Service Service Service Service Endpoint Endpoint Endpoint Endpoint Endpoint
23. Escalation 23 Cluster Node Node Service Service Service Service Service Endpoint Endpoint Endpoint Endpoint Endpoint
24. Escalation 24 Cluster Node Node Service Service Service Service Service Endpoint Endpoint Endpoint Endpoint Endpoint
25. Escalation 25 Cluster Node Node Service Service Service Service Service Endpoint Endpoint Endpoint Endpoint Endpoint
26. Redundancy Cost Active/Active Active/Standby N+M
 Active/Passive Cost Time To Recover 26
27. The Fault Observer receives system and error events and can guide and orchestrate detection and recovery Unit Unit Observer Listener Listener Unit Unit 27
30. Detecting Errors 30
31. A silent system is a dead system. 31
32. A System Monitor helps to study behaviour and to make sure it is operating as specified. http://upload.wikimedia.org/wikipedia/commons/3/3b/Mission_control_center.jpg 32
33. https://github.com/Netflix/Turbine 33
34. Periodic Checking Heartbeats monitor tasks or remote services and initiate recovery Routine Exercises prevent idle unit starvation and surface malfunctions 34
35. 35 Encoder( Encoder( Ne*y( Writes( Ne*y( Reads( Decoder( Decoder( Event on Idle No Traffic Endpoint
36. Riding over Transients is used to defer error recovery if the error is temporary. “‘Patience is a virtue’ to allow the true signature of an error to show itself.” - Robert S. Hanmer 36
38. And more! • Complete Parameter Checking • Watchdogs • Voting • Checksums • Routine Audits 38
39. Recovery and Mitigation of Errors 39
40. Timeout to not wait forever and keep holding up the resource. 40 X
41. Failover to a redundant unit when the error has been detected and isolated. Cost Active/Active Active/Standby N+M Cost Time To Recover Redundancy
 Reminder 41
42. Intelligent Retries Time between Retries Number of Attempts Fixed Linear Exponential 42
43. Restart can be used as a last resort with the trade-off to lose state and time. 43
44. Fail Fast to shed load and give a partial great service than a complete bad one. Boundary 44
45. Backpressure & Batching! 45
46. Case Study: Hystrix https://raw.githubusercontent.com/wiki/Netflix/Hystrix/images/hystrix-flow-chart-original.png 46
47. And more! • Rollback • Roll-Forward • Checkpoints • Data Reset Recovery Mitigation • Bounded Queuing • Expansive Controls • Marking Data • Error Correcting Codes 47
48. And more! • Rollback • Roll-Forward • Checkpoints • Data Reset Recovery Mitigation • Bounded Queuing • Expansive Controls • Marking Data • Error Correcting Codes 48
49. Recommended Reading 49
50. Patterns for Fault-Tolerant Software by Robert S. Hanmer 50
51. Release It! by Michael T. Nygard 51
52. Any Questions? 52
53. twitter @daschl email michael.nitschinger@couchbase.com Thank you! 53