Microservices In Practice

Irakli Nadareishvili,

Director of Strategy, API Academy

CA Technologies

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But, why?

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Microservices can greatly improve your capabilities in:

CONTINUOUSDELIVERY

PRODUCINGEVOLVABLEANDSCALABLEARCHITECTURE

ENABLINGAGILESOFTWAREDEVELOPMENTLIFECYCLE

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COMMUNICATEUSINGLANGUAGE-AGNOSTICAPIS

AREINDEPENDENTLYDEPLOYABLEVIAUNIVERSALCONTAINERS

PRACTICEDECENTRALIZEDDATAMANAGEMENT

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Microservices is an architectural style, in which a complex software application is de-composed into smaller components ("micro services") that:

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Challenge:De-centralized Data Management

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Tool 1:Think of Capabilities,

not: Data Models

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Bounded Contexts

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Eric Evans: Bounded ContextsAn application domain consists of multiple bounded contexts. Residing within each BC are models that do not need to be shared outside, as well as other models that are shared externally.

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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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Caution: DDD and Bounded Context Identification

Are Far From Trivial or Easy Tasks

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Domain-Driven Design – More Information

Eric Evans: "Domain-Driven Design: Tackling Complexity in the Heart of Software" - 2003

Vaughn Vernon: "Implementing Domain-Driven Design" - 2013

Scott Millett: "Patterns, Principles, and Practices of Domain-Driven Design" - 2015

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Tool 2: Event Sourcing & CQRS

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Event SourcingUse an append-only store to record the full series of events that describe actions taken on data in a domain, rather than storing just the current state, so that the store can be used to materialize the domain objects.

https://msdn.microsoft.com/en-gb/library/dn589792.aspx

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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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Deposit Money Microservice

Deposit MessageQueue EventStore(e.g.Cassandra)

Transactions List/Query Microservice

Query IndexStore(e.g.ElasticSearch)

Validation

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What About Them Transactions?

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Tool 3: Sagas (Long-LivedDistributedTransactions)

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Booking Travel

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No Shared State = No Distr. Transactions

Source:http://vasters.com/clemensv/2012/09/01/Sagas.aspx

We ♥ Sagas!Designedby:HectorGarcia-Molina&KennethSalem,Princeton,1987

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One More Thing…

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“Bounded context should be asbig as it needs to be in order tofully express its completeUbiquitous Language”

– Vaughn Vernon, Implementing Domain –Driven Design.

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Many start coarse-grained and become more granular over time.

That said, companies that have been building Microservices for long, report that they end with hundredsof Microservices.

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Where do we gethundreds of servers?

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How do we afford so many servers?

DirectorofStrategy,APIAcademyIrakliNadareishvili

@inadarei

@apiacademy

@cainc