distributed architecture patterns cqrs & event...

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Distributed Architecture Patterns

CQRS & Event Sourcing


Dylan SmithSenior ALM Consultant

Application Lifecycle Expert

PROFILEDylan is an ALM (Application Lifecycle Management) consultant for Imaginet where he spends his time helping teams become more successful at delivering software. Dylan has over a decade experience designing and architecting mission critical applications. In the past 5 years Dylan has focused on agile development techniques and practices. He has led the shift to agile and lean development practices across multiple teams, projects and companies.

“CQRS+ES differs from most design patterns in that it provides clear business benefits in addition to the obvious technical benefits.”


Overview• Review Typical

Architecture• What is CQRS?• What is Event Sourcing?• CODE !!!• Benefits / Concerns


Data StorageData Storage

Domain Object

Domain Object

Application ServicesApplication Services

Remote FacadeRemote Facade

ClientClient

Request DTODTO ReturnedRequest DTODTO Returned

Send DTOStatus Returned

Send DTOStatus Returned

RepositoryRepository

Domain ObjectDomain Object

Typical Distributed Architecture




Command HandlersCommand Handlers


ClientClient

Request DTODTO

Returned

Request DTODTO

Returned

Send CommandAck/Nak

Response

Send CommandAck/Nak

Response



Query HandlersQuery Handlers



CQRS


Sample Read Data Model


Purchase Order

Purchase Order

Line Items (n)Line Items (n)

Shipping InformationShipping

Information


Order CreatedOrder

CreatedAdded 4

HatsAdded 4

HatsAdded 2

ShirtsAdded 2

Shirts

Shipping Info

Added

Shipping Info

Added


Event StoreEvent Store


Command HandlersCommand Handlers


ClientClient

Request DTODTO

Returned

Request DTODTO

Returned

Send CommandAck/Nak

Response

Send CommandAck/Nak

Response



Query HandlersQuery Handlers


Data StorageData StorageEvent BusEvent Bus

CQRS + ES

Event

HandlersE

vent H

andlers


Event Store Data Model



Command


Event


Command Handler


Domain Object


Event Handler


Query Handler


Data Transfer Object



vs


Scalability




Sample Unit Test


Sample Unit Test #2




ClientClient

DomainDomain Read ModelRead Model

Events

Commands DTOs



NoSQL Databases


Other Topics(Time Permitting)• Event Versioning• When to use CQRS/ES?• Using CQRS or ES separately• Concurrency• Eventual Consistency• Asynchronous Commands


Recommended Reading


Sample CodeSuper Simple CQRS Example

github.com/gregoryyoung/m-rNCQRS

ncqrs.orgThe CQRS Kitchen

thecqrskitchen.codeplex.comLokad-CQRS

code.google.com/p/lokad-cqrsFohjin

github.com/MarkNijhof/Fohjin


SummaryCQRS – Enables specialization:

of design/architecture, and people

Event Sourcing – All about capturing intent and not losing data


Questions?

distributed architecture patterns cqrs & event...

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