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Decouple all the things - asynchronous messagin...

Decouple all the things - asynchronous messaging keeps it simple

Talk at YAPC::EU 2015

Kerstin Puschke

September 04, 2015
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  1. inform about update Master data updates need to propagate 15

    customer data customer out of business orders support contracts
  2. downside of REST: client misses update if temporarily down 16

    customer data orders support contracts
  3. downside of REST: master data app needs to know its

    clients 17 customer data orders support contracts invoices
  4. amqp.org/about/what “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 “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.”
  5. Messages contain payload and routing key 25 Routing Key Payload

    •  application data – any form, any encoding… …and more •  Structured app-specific data (properties / attributes) •  Headers •  Annotations •  …
  6. Add consumers without touching producer 28 P X Q2 Q1

    C1 C2 Producer Exchange Queue Consumer
  7. Different messages for different client needs 30 master data client

    Owns additional user data related to master data •  User account aka master data record removed Caches master data •  If master data updated or removed Mirrors master data •  Updated master data
  8. Why not include updated data? routing key <...>profile.updated payload 34

    { “user_id”: 42, “fields”: [“last_name”] }
  9. 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 Small payload •  easier on the broker •  just enough data for consumer to decide about making REST request 35
  10. 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 Lost messages •  acceptable for usecase? •  e.g. consider rebuilding mirror / cache occasionally 36
  11. Centralized tracking of decentralized events 38 P1 P2 X Q

    C event to be tracked tracking counter ++
  12. Task / Command – consumer state to change 41 Message

    Broker X Q P C event / state change
  13. Run tasks asynchronously 43 Message Broker X Q P C

    image upload user facing image processing
  14. Improve response time, avoid downtimes, gain reliability 45 Message Broker

    X Q P C image upload user facing image processing
  15. Scaling on the fly 46 X Q C C P

    migration trigger data migration
  16. Test without impacting users 48 Message Broker X Q P

    C old app user facing shadow calls to new app
  17. Flexible Routing via different Exchange Types Direct Exchange •  routes

    to all queues whose binding_key equals routing_key Fanout Exchange •  broadcasts to every queue it has a binding for •  ignores routing key and queue name Topic Exchange •  dot-separated words as routing keys, plus wildcards •  routing on multiple attributes Header Exchange •  based on headers, not routing keys •  routing on multiple attributes 50
  18. In a nutshell •  Interoperability •  Improve response times • 

    Avoid downtimes •  Robustness & Reliability •  Scale on the fly •  Reduce complexity •  Simplify code 51
  19. Who am I Contact •  http://www.kpuschke.eu •  twitter: @titanoboa42 • 

    https://www.xing.com/profile/ Kerstin_Puschke Senior Software Engineer at XING Hamburg •  xing.com social network for business professionals •  debian, perl, javascript, ruby on rails, mysql, redis, riak, . . . We’re hiring! http://corporate.xing.com/ english/company/careers- at-xing/