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PatternsResiliency_DevDays2019.pdf

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We have traditionally built robust software systems by trying to avoid mistakes and by dodging failures when they occur in production or by testing parts of the system in isolation from one another. Modern methods and techniques take a very different approach based on resiliency, which promotes embracing failure instead of trying to avoid it. Resilient architectures enhance observability, leverage well-known patterns such as graceful degradation, timeouts and circuit breakers but also new patterns like cell-based architecture and shuffle sharding. In this session, will review the most useful patterns for building resilient software systems and especially show the audience how they can benefit from the patterns.

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PatternsResiliency_DevDays2019.pdf

  1. 1. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. N O R D I C S
  2. 2. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Resiliency and Availability Design Patterns for the Cloud Adrian Hornsby Sr. Technical Evangelist Amazon Web Services
  3. 3. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Distributed Systems are hard
  4. 4. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Complex systems Amazon Twitter Netflix
  5. 5. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Partial failure mode
  6. 6. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Resiliency: Ability for a system to handle and eventually recover from unexpected conditions
  7. 7. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. How do we build resilient software systems?
  8. 8. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. …
  9. 9. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. “Quality is not an act, it is a habit” Aristotle, some time around 350BC
  10. 10. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. https://aws.amazon.com/wellarchitected
  11. 11. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Let’s talk about Multi-AZ
  12. 12. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Multi-AZ architecture Region Availability zone a Availability zone b Availability zone c Instances Instances Instances DB Instance DB instance standby
  13. 13. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Multi-AZ architecture Region Availability zone a Availability zone b Availability zone c Instances Instances Instances DB Instance DB instance standby X
  14. 14. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Multi-AZ architecture Region Availability zone a Availability zone b Availability zone c Instances Instances Instances DB Instance DB instance standby X
  15. 15. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Multi-AZ architecture Region Availability zone a Availability zone b Availability zone c Instances Instances Instances DB Instance X
  16. 16. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Multi-AZ architecture • Enables fault-tolerant applications • AWS regional services designed to withstand AZ failures • Leveraged by most AWS regional services (S3, DynamoDB, ELBs, …) Region Availability zone a Availability zone b Availability zone c Instances Instances Instances DB Instance DB instance standby
  17. 17. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Region Availability zone a Availability zone b Availability zone c Application
  18. 18. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Region Availability zone a Availability zone b Availability zone c Application
  19. 19. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Cascading Failures
  20. 20. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Better to react without reacting
  21. 21. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Region Availability zone a Availability zone b Availability zone c Application
  22. 22. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. But Why?
  23. 23. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. 3 AZ’s is better than 2
  24. 24. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Region Availability zone a Availability zone b Availability zone c Application Requires 8 Instances
  25. 25. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Region Availability zone a Availability zone b Availability zone c Application Requires 6 Instances
  26. 26. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Let’s talk about auto scaling
  27. 27. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Auto-Scaling FixedVariable
  28. 28. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Availability zone 1 Auto Scaling group AWS Region Availability zone 2 Auto-scaling for self-healing X
  29. 29. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved.
  30. 30. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Let’s talk about decoupling and async
  31. 31. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Process A Process B Process A Process B Synchronous Asynchronous Waiting Working Continues get or fetch resultGet result Decoupling with async pattern
  32. 32. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. API: {DO foo} PUT JOB: {JobID: 0001, Task: DO foo} API: {JobID: 0001} GET JOB: {JobID: 0001, Task: DO foo} {JobID: 0001, Result: bar} Cache node Worker Instance Worker Instance Queue/Streaming API Instance API Instance API Instance
  33. 33. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Push Notification User Worker Instance Worker Instance API Instance API Instance Cache node Fetch results API Instance Queue/Streaming
  34. 34. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Degrade & prioritize traffic with queues Worker Instance Worker Instance API Instance API Instance API Instance HighPriorityQueue LowPriorityQueue
  35. 35. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Let’s talk about timeouts, backoff & retries!
  36. 36. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Users App DB Conn Pool INSERT INSERT INSERT INSERT What happens if the DB “slows down”? Timeout client side Timeout backend side ??
  37. 37. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. User 1 App DB Conn Pool INSERT Timeout client side = 10s Timeout backend side = default = Infinite Retry INSERT Retry INSERT ERROR: Failed to get connection from pool Retry
  38. 38. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved.
  39. 39. https://dev.mysql.com/doc/connector-j/5.1/en/connector-j-reference-configuration-properties.html
  40. 40. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Set the timeouts!
  41. 41. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. How else could we have prevented the error? User 1 DB Conn Pool INSERT Retry INSERT Retry INSERT Retry ERROR: Failed to get connection from pool
  42. 42. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. User 1 DB Conn Pool INSERT Timeout client side = 10s Timeout backend side = 10s Wait 2s before Retry INSERT INSERT Wait 4s before Retry Wait 8s before Retry Wait 16s before Retry Backing off between retries Releasing connectionsBackoff
  43. 43. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. No jitter With jitter https://aws.amazon.com/blogs/architecture/exponential-backoff-and-jitter/ Simple Exponential Backoff is not enough: Add Jitter
  44. 44. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Example: add jitter 0-1000ms def get_item(self, url, n=1): MAX_TRIES = 12 try: res = requests.get(url) except: if n > MAX_TRIES: return None n += 1 time.sleep((2 ** n) + (random.randint(0, 1000) / 1000.0)) return self.get_item(url, n) else: return res
  45. 45. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Idempotent operation No additional effect if it is called more than once with the same input parameters.
  46. 46. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Circuit Breaker • Wrap a protected function call in a circuit breaker object, which monitors for failures. • If failures reach a certain threshold, the circuit breaker trips. Producer Circuit Breaker Consumer Connection Monitoring Timeouts Breaking Circuit
  47. 47. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. https://spring.io/guides/gs/circuit-breaker/
  48. 48. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Let’s talk about health checking!
  49. 49. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Auto Scaling group Service A Availability zone 1 Auto Scaling group AWS Region Service A Availability zone 2 Service BService B database Email Probing for health Cluster
  50. 50. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Shallow health check Instance Cache node Email database Cluster Are you healthy? yes
  51. 51. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Shallow health check Instance Cache node Email database Cluster Are you healthy? yes
  52. 52. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Deep health check Instance Cache node Email database Cluster Are you healthy? yes Are you healthy? yes yes yes yes
  53. 53. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Deep health check Instance Cache node Email database Cluster Are you healthy? no Are you healthy? no yes yes yes
  54. 54. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Prioritize shallow health checks during hard times. Cache.
  55. 55. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Let’s talk about load shedding.
  56. 56. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved.
  57. 57. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved.
  58. 58. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Cheaply reject excess work
  59. 59. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved.
  60. 60. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Be careful when selecting the right metric
  61. 61. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Don’t be overly optimistic and take on more than you can. Find an operational metric to reject what you cannot take in. Favor cached and static content Prioritize ELB health check (shallow) pings In an overload situation you have precious resources, do not let any of it go to waste. Load Shedding
  62. 62. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Service Degradation & Fallbacks
  63. 63. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Let’s talk about databases!
  64. 64. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Database Federation Users DB Products DB Instance InstanceInstance DB Instance DB instance read replica DB Instance DB instance read replica
  65. 65. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Database Sharding User ShardID 002345 A 002346 B 002347 C 002348 B 002349 A CBA Instance InstanceInstance DB Instance DB instance read replica DB Instance DB instance read replica DB Instance DB instance read replica
  66. 66. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Read / Write separation DB Instance DB instance read replica DB instance read replica DB instance read replica Instance InstanceInstance Supports degradation through Read-Only mode
  67. 67. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Transient state does not belong in the database.
  68. 68. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Let’s talk about shuffle sharding.
  69. 69. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved.
  70. 70. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. X X X X X X XX ♤♡♢ ⚀ ⚁ ⚂ ⚃♧♢
  71. 71. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Cascading Failures
  72. 72. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Measure for this: blast radius
  73. 73. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved.
  74. 74. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Cell-based architecture XX ♤♡♢ ⚀ ⚁ ⚂ ⚃♧♢
  75. 75. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Shuffle sharding XX ♤♡♢ ⚀ ⚁⚂ ⚃♡ ♤ ♧♢ ⚀⚂♧ ⚁⚃♢ ♢ ♡ ♧♢
  76. 76. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Shuffle sharding Nodes = 8 Shard size = 2 Combinations = 28 Overlap % customers 0 53.6% 1 42.8% 2 3.6%
  77. 77. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Shuffle sharding Nodes = 100 Shard size = 5 Combinations = 75 million! Overlap % customers 0 77% 1 21% 2 1.8% 3 0.06% 4 0.0006% 5 0.0000013%
  78. 78. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Shuffle sharding
  79. 79. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Let’s talk about chaos!
  80. 80. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Fire Drills
  81. 81. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. GameDay at Amazon Creating Resiliency Through Destruction https://www.youtube.com/watch?v=zoz0ZjfrQ9s
  82. 82. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Chaos engineering https://github.com/Netflix/SimianArmy
  83. 83. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. “Chaos Engineering is the discipline of experimenting on a distributed system in order to build confidence in the system’s capability to withstand turbulent conditions in production.” http://principlesofchaos.org
  84. 84. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Failure injection • Start small & build confidence • Application level • Host failure • Resource attacks (CPU, memory, …) • Network attacks (dependencies, latency, …) • Region attacks • “Paul” attack
  85. 85. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Plan for the worst, prepare for the unexpected.
  86. 86. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved.
  87. 87. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved.
  88. 88. Thank you! © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Adrian Hornsby @adhorn https://medium.com/@adhorn https://speakerdeck.com/adhorn/patterns-for-building-resilient-software-systems-2019

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