Decouple all the things: Asynchronous messaging keeps it simple

Talk at Codemotion Berlin 2016

Transcript

1. Decouple all the things
   Asynchronous messaging keeps it simple
   Kerstin Puschke
   @titanoboa42
   
   Codemotion Berlin 2016
   

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2. Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 2
   Machine to Machine
   Communication
   
   

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3. Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 3
   418 I’m a teapot
   

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4. Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 4
   Improving
   maintainablity and stability
   with
   asynchronous
   communication
   
   

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5. Index
   Synchronous Communication
   Asynchronous Messaging with AMQP
   Publish - Subscribe
   Task Queue
   Code & Demo
   Summary
   Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 5
   

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6. Synchronous
   Communication
   and its disadvantages
   Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 6
   

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7. Updates need to propagate
   from the owner of the data to its clients
   Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 7
   inform about
   update
   business partners
   business partner
   out of business
   orders
   support
   contracts
   

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8. downside of REST:
   client misses update if temporarily down
   Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 8
   business partners
   orders
   support
   contracts
   

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9. downside of REST:
   app needs to know its clients
   Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 9
   business partners
   orders
   support
   contracts
   invoices
   

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10. Updates need to propagate
    Example from xing.com
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 10
    member profile
    (cv)
    new job title
    events
    …
    

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11. Asynchronous
    Messaging
    using the Advanced Message Queuing Protocol
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 11
    

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12. Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 12
    Advanced Message
    Queuing Protocol
    

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13. Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 13
    “The capable, commoditized,
    multi-vendor communications
    ecosystem which AMQP enables
    “The capable, commoditized,
    multi-vendor communications
    ecosystem which AMQP enables
    creates opportunities for
    commerce and innovation
    
    “The capable, commoditized,
    multi-vendor communications
    ecosystem which AMQP enables
    creates opportunities for
    commerce and innovation which
    can transform the way business
    is done on the Internet,
    
    “The capable, commoditized,
    multi-vendor communications
    ecosystem which AMQP enables
    creates opportunities for
    commerce and innovation which
    can transform the way business
    is done on the Internet, and in
    the cloud.”
    amqp.org/about/what
    Bingo,
    anyone?
    

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14. Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 14
    “open standard application layer
    protocol for message-oriented
    middleware”
    https://en.wikipedia.org/wiki/
    Advanced_Message_Queuing_Protocol
    

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15. Interoperability
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 15
    message
    broker
    message
    consumer
    message
    producer
    

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16. Messages contain payload and routing key
    •  Routing Key
    •  Payload
    -  application data
    -  any form, any encoding…
    •  …and more
    -  Structured app-specific data (properties / attributes)
    -  Headers, Annotations
    -  …
    
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 16
    

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17. Message Flow
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 17
    Producer Exchange
    
    Queue
    
    Consumer
    P
    Message Broker
    X Q C
    

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18. No information lost if consumer down
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 18
    Producer Exchange
    
    Queue
    
    Consumer
    P
    Message Broker
    X Q C
    

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19. Applications are in power
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 19
    Producer Exchange
    
    Queue
    
    Consumer
    P
    Message Broker
    X Q C
    

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20. Producer does not have to know consumers
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 20
    Producer Exchange
    
    Queue
    
    Consumer
    P
    
    X
    Q2
    Q1 C1
    C2
    

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21. Publish Subscribe
    using the Advanced Message Queuing Protocol
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 21
    

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22. Propagating updates
    Clients have different needs – use different messages
    
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 22
    owner of
    updated data
    owner of
    related data
    mirror
    cache
    

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23. Example message
    Routing key
    <…>.user.deleted
    Payload
    
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 23
    {
    “user_id” : 42
    }
    
    

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24. Example message
    Routing key
    <…>.profile.updated
    Payload
    
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 24
    {
    “user_id” : 42,
    “fields” : [ “country”, “city” ]
    }
    
    

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25. Flexible routing via different exchange types
    •  Direct Exchange
    -  routes to all queues whose binding_key equals
    routing_key
    •  Topic Exchange
    -  routing on multiple attributes
    -  dot-separated words as routing keys, plus wildcards
    •  Header Exchange
    -  routing on multiple attributes based on headers
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 25
    

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26. Flexible routing via different exchange types
    •  Fanout Exchange
    -  broadcasts to every queue it has a binding for
    -  ignores routing key and queue name
    
    
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 26
    

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27. Don’t include updated data
    Routing key
    <…>.profile.updated
    Payload
    
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 27
    {
    “user_id” : 42,
    “fields” : [ “country”, “city” ]
    }
    
    

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28. No guaranteed order – aim for commutativity
    •  Order of messages not guarantueed
    •  Commutativity
    •  Complement with synchronous API (e.g. REST)
    -  most recent data
    -  leading system
    -  message consumers follow up with REST if necessary
    
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 28
    

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29. No exactly-once delivery
    aim for idem-potent messages
    •  Duplicated messages
    -  possible e.g. if producer re-sends message after
    connection failure
    -  use idem-potent message handling
    
    
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 29
    

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30. Consumer does not have to know producers
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 30
    Producer Exchange
    
    Queue
    
    Consumer
    
    X
    P2
    P1
    Q C
    

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31. Centralized tracking of decentralized events
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 31
    
    X
    P2
    P1
    Q C
    event to be
    tracked
    tracking
    counter ++
    

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32. Avoid n-m routing
    Keep breaking changes manageable
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 32
    
    X
    Q2
    Q1
    P2
    P1
    P1
    P2
    C1
    C1
    C2
    C2
    

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33. Notifications / Events
    producer state change
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 33
    
    X Q C
    event
    state changed
    P
    

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34. Task / Command
    consumer state to change
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 34
    
    X Q C
    event
    state change
    P
    

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35. Task Queue
    using the Advanced Message Queuing Protocol
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 35
    

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36. Run tasks asynchronously
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 36
    
    X Q C
    image upload
    user facing
    image
    processing
    P
    

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37. Improve response time
    Avoid downtimes
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 37
    
    X Q C
    image upload
    user facing
    image
    processing
    P
    

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38. Scaling on the fly
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 38
    
    X Q
    migration
    trigger
    data
    migration
    P
    C1
    C2
    

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39. Migration without downtime
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 39
    
    X Q C
    old system
    user facing
    new system
    P
    

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40. Test without impacting user
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 40
    
    X Q C
    old system
    user facing
    shadow calls
    P
    

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41. Example
    using the Advanced Message Queuing Protocol
    in Ruby
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 41
    

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42. Ruby example
    Connect to the broker
    require "bunny"
    connection = Bunny.new
    connection.start
    channel = connection.create_channel
    
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 42
    

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43. Ruby example
    Create queue
    task_queue = channel.queue(
    "awesome_task_queue",
    durable: true
    )
    
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 43
    

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44. Ruby example
    Publish message
    msg = "Hello “+Time.now.strftime('%T')
    channel.default_exchange.publish(
    msg,
    routing_key: task_queue.name,
    persistent: true
    )
    
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 44
    

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45. Ruby example
    Consume message
    task_queue.subscribe(block: true) do
    |delivery_info, properties, payload|
    puts "Received '#{payload}'”
    sleep 2 # hard work
    end
    
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 45
    

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46. Demo
    
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 46
    

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47. In a nutshell
    •  Interoperability
    •  Improve response times
    •  Avoid downtimes
    •  Scale on the fly
    •  Simplify code
    •  Easy to get started
    Decouple all the things / Kerstin Puschke / @titanoboa42 / Codemotion Berlin 2016 47
    

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48. Decouple all the things
    Asynchronous messaging keeps it simple
    Kerstin Puschke
    @titanoboa42
    
    Codemotion Berlin 2016
    We‘re hiring
    xing.com/careers
    

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