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
   

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2. the right
   Mindset
   2
   

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3. – U.S. Marine Corps
   “The more you sweat in peace, the less
   you bleed in war.”
   3
   

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6. Not so fast, mister fancy tests!
   6
   

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7. What can go wrong?
   Always ask yourself
   7
   

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8. Fault Tolerance
   101
   8
   

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9. Fault Error Failure
   A fault is a latent defect that can cause an
   error when activated.
   9
   

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10. Fault Error Failure
    Errors are the manifestations of faults.
    10
    

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11. Fault Error Failure
    Failure occurs when the service no longer
    complies with its specifications.
    11
    

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12. Fault Error Failure
    Errors are inevitable. We need to
    detect, recover and mitigate
    them before they become failures.
    12
    

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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
    

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14. Availability
    is the percentage of time the system is able to
    perform its function.
    availability =
    MTTF
    MTTF + MTTR
    14
    

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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
    

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16. Pop Quiz!
    Edge Service
    User Service Session Store Data Warehouse
    Wanted: 99.99% Availability
    ??? ??? ???
    16
    

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17. Pop Quiz!
    Edge Service
    User Service Session Store Data Warehouse
    Wanted: 99.99% Availability
    99.99%
    17
    99.99% 99.99%
    

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18. Pop Quiz!
    Edge Service
    User Service Session Store Data Warehouse
    Wanted: 99.99% Availability
    ~99.999% ~99.999% ~99.999%
    18
    

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19. Fault Tolerant
    Architecture
    19
    

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20. Units of Mitigation
    are the basic units of
    error containment and recovery.
    20
    

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21. Escalation
    is used when recovery or mitigation
    is not possible inside the unit.
    21
    

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22. Escalation
    22
    Cluster
    Node Node
    Service Service Service Service Service
    Endpoint Endpoint Endpoint Endpoint Endpoint
    

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23. Escalation
    23
    Cluster
    Node Node
    Service Service Service Service Service
    Endpoint Endpoint Endpoint Endpoint Endpoint
    

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24. Escalation
    24
    Cluster
    Node Node
    Service Service Service Service Service
    Endpoint Endpoint Endpoint Endpoint Endpoint
    

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25. Escalation
    25
    Cluster
    Node Node
    Service Service Service Service Service
    Endpoint Endpoint Endpoint Endpoint Endpoint
    

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26. Redundancy
    Cost
    Active/Active Active/Standby N+M

    Active/Passive
    Cost Time To Recover
    26
    

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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
    

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30. Detecting
    Errors
    30
    

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31. A silent system
    is a dead system.
    31
    

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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
    

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33. https://github.com/Netflix/Turbine
    33
    

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34. Periodic Checking
    Heartbeats monitor tasks or remote services
    and initiate recovery
    Routine Exercises prevent idle
    unit starvation and surface malfunctions
    34
    

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35. 35
    Encoder(
    Encoder(
    Ne*y(
    Writes(
    Ne*y(
    Reads(
    Decoder(
    Decoder(
    Event on Idle
    No Traffic
    Endpoint
    

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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
    

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38. And more!
    • Complete Parameter Checking
    • Watchdogs
    • Voting
    • Checksums
    • Routine Audits
    38
    

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39. Recovery and Mitigation
    of Errors
    39
    

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40. Timeout
    to not wait forever and keep
    holding up the resource.
    40
    X
    

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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
    

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42. Intelligent Retries
    Time between Retries
    Number of Attempts
    Fixed Linear Exponential
    42
    

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43. Restart
    can be used as a last resort with the
    trade-off to lose state and time.
    43
    

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44. Fail Fast
    to shed load and give a partial great service
    than a complete bad one.
    Boundary
    44
    

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45. Backpressure
    & Batching!
    45
    

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46. Case Study: Hystrix
    https://raw.githubusercontent.com/wiki/Netflix/Hystrix/images/hystrix-flow-chart-original.png
    46
    

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47. And more!
    • Rollback
    • Roll-Forward
    • Checkpoints
    • Data Reset
    Recovery Mitigation
    • Bounded Queuing
    • Expansive Controls
    • Marking Data
    • Error Correcting Codes
    47
    

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48. And more!
    • Rollback
    • Roll-Forward
    • Checkpoints
    • Data Reset
    Recovery Mitigation
    • Bounded Queuing
    • Expansive Controls
    • Marking Data
    • Error Correcting Codes
    48
    

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49. Recommended
    Reading
    49
    

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50. Patterns for
    Fault-Tolerant Software
    by Robert S. Hanmer
    50
    

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51. Release It!
    by Michael T. Nygard
    51
    

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52. Any
    Questions?
    52
    

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53. twitter
    @daschl
    email
    michael.nitschinger@couchbase.com
    Thank you!
    53
    

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