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Microservices Architecture: The Blind Spots Irakli Nadareishvili, Director of Strategy, API Academy CA Technologies Deck: http://bit.ly/microservices-blindspots

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2 © 2015 CA. ALL RIGHTS RESERVED. inadarei

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3 © 2015 CA. ALL RIGHTS RESERVED. inadarei #1 What Drives Microservices Adoption? ¯\_(ツ)_/¯

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4 © 2015 CA. ALL RIGHTS RESERVED. inadarei

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5 © 2015 CA. ALL RIGHTS RESERVED. inadarei Technology Heterogeneity Partitioned Scalability (per microservice) Independent Deployments Compose-ability Optimized for Replace-ability 1 2 3 4 5 Key Benefits of Microservices(as of 2015)

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6 © 2015 CA. ALL RIGHTS RESERVED. inadarei Motivations for Adoption Will Change The reasons why MSA became popular are not the same reasons why it will become ubiquitous Source: Crossing the Chasm – Geoffrey A. Moore

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7 © 2015 CA. ALL RIGHTS RESERVED. inadarei Docker is a "gateway drug" for MSA

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8 © 2015 CA. ALL RIGHTS RESERVED. inadarei Containerization will drive MSA Adoption to the extent that: Microserviceswon't be a "choice" Prediction:

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9 © 2015 CA. ALL RIGHTS RESERVED. inadarei #2 Current Focus Is Too Code-Centric

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10 © 2015 CA. ALL RIGHTS RESERVED. inadarei Caution: Coupling of service interfaces is every bit as toxic as the code one, and can render entire architecture useless. Hypermedia design, with its high degree of interface de-coupling can be of huge help here.

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11 © 2015 CA. ALL RIGHTS RESERVED. inadarei #3 Decentralized Data

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12 © 2015 CA. ALL RIGHTS RESERVED. inadarei

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13 © 2015 CA. ALL RIGHTS RESERVED. inadarei DDD & Bounded Contexts

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14 © 2015 CA. ALL RIGHTS RESERVED. inadarei Bounded Context = Capabilities. “In your organization, you should be thinking not in terms of data that is shared, but about the capabilities those contexts provide the rest of the domain.” – Sam Newman, Building Microservices

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15 © 2015 CA. ALL RIGHTS RESERVED. inadarei

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16 © 2015 CA. ALL RIGHTS RESERVED. inadarei “Bounded context should be as big as it needs to be in order to fully express its complete Ubiquitous Language” – Vaughn Vernon, Implementing Domain –Driven Design.

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17 © 2015 CA. ALL RIGHTS RESERVED. inadarei Inherent Conflict: Business teams actually don't favor small bounded contexts (due to diff. ubiquitous language). For tech: continuous Integration is easier with smaller teams and codebases.

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18 © 2015 CA. ALL RIGHTS RESERVED. inadarei In general: DDD alone will not be able to give you small enough microservices and/or solve data embedding requirements.

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19 © 2015 CA. ALL RIGHTS RESERVED. inadarei Data Storage Alternative: Event Sourcing & CQRS

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20 © 2015 CA. ALL RIGHTS RESERVED. inadarei CRUD-Oriented System Model Patient Demographics Clinical Notes (3) Billing Information Insurances (2) Visits (3)

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21 © 2015 CA. ALL RIGHTS RESERVED. inadarei "Event Sourcing is all about storing facts and any time you have "state" (structural models) – they are first-level derivative off of your facts. And they are transient." - Greg Young

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22 © 2015 CA. ALL RIGHTS RESERVED. inadarei Command and Query Responsibility Segregation (CQRS) Segregate operations that read data from operations that update data by using separate interfaces. This pattern can maximize performance, scalability, and security; support evolution of the system over time through higher flexibility; and prevent update commands from causing merge conflicts at the domain level. https://msdn.microsoft.com/en-us/library/dn568103.aspx

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23 © 2015 CA. ALL RIGHTS RESERVED. inadarei "Current State"-Oriented System Model Patient Demographics Clinical Notes (3) Billing Information Insurances (2) Visits (3)

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24 © 2015 CA. ALL RIGHTS RESERVED. inadarei Events-based Model Patient Created Insurance Added Insurance Added Billing Info Added Visit's Clinical NoteAdded Visit's Clinical NoteAdded Visit's Clinical NoteAdded Visit's Clinical NoteAdded Visit's Clinical NoteAdded Visit's Clinical NoteAdded Visit's Clinical NoteAdded … Visit Added Visit Added Visit Added

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25 © 2015 CA. ALL RIGHTS RESERVED. inadarei "Patient Visits" Microservice Visit Message Queue Facts Store (e.g. Cassandra) "List Patient Visits by a Doctor" Microservice Query Index Store (e.g. ElasticSearch) Validation

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26 © 2015 CA. ALL RIGHTS RESERVED. inadarei Do Not Overuse ES or CQRS! You should only use Event Sourcing and CQRS when necessary. It is not an architecture for your entire system, but a tool to be used sparingly.

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27 © 2015 CA. ALL RIGHTS RESERVED. inadarei What About Them Transactions? Use: Sagas (Long-Lived Distributed Transactions) @see: http://vasters.com/clemensv/2012/09/01/Sagas.aspx Designed by: Hector Garcia-Molina & Kenneth Salem, Princeton, 1987

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28 © 2015 CA. ALL RIGHTS RESERVED. inadarei One More Thing…

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29 © 2015 CA. ALL RIGHTS RESERVED. inadarei http://martinfowler.com/bliki/MicroservicePrerequisites.html I really, really hated this message, so I did smth. about it

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30 © 2015 CA. ALL RIGHTS RESERVED. inadarei https://github.com/apiacademy /microservices-deployment

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Director of Strategy, API Academy Irakli Nadareishvili @inadarei @apiacademy @cainc http://bit.ly/microservices-blindspots