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vladikk doit-intl.com #ndcsydney THE DARK SIDE OF EVENTS

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vladikk doit-intl.com #ndcsydney @vladikk vladikk.com DoiT International

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vladikk doit-intl.com #ndcsydney

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vladikk doit-intl.com #ndcsydney SOFTWARE ARCHITECTURE

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vladikk doit-intl.com #ndcsydney "Architecture is about the important stuff, whatever that is” - Ralph Johnson

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vladikk doit-intl.com #ndcsydney SOFTWARE SOLVES BUSINESS PROBLEMS GOOD DESIGN SUPPORTS THE BUSINESS

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vladikk doit-intl.com #ndcsydney Infrastructure Databases Architectural styles Frameworks Languages Methodologies Accidental Complexity

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vladikk doit-intl.com #ndcsydney …and it’s hard!!! GOOD DESIGN SUPPORTS THE BUSINESS SOFTWARE SOLVES BUSINESS PROBLEMS

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vladikk doit-intl.com #ndcsydney THE GOAL OF SOFTWARE ARCHITECTURE IS TO MANAGE COMPLEXITY!

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vladikk doit-intl.com #ndcsydney 1. Component level 2. System level 3. Implementation level Complexity Management

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vladikk doit-intl.com #ndcsydney Local Complexity

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vladikk doit-intl.com #ndcsydney Global Complexity

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vladikk doit-intl.com #ndcsydney Global Complexity

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vladikk doit-intl.com #ndcsydney ARCHITECTURE = BOUNDARIES DESIGN

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vladikk doit-intl.com #ndcsydney

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vladikk doit-intl.com #ndcsydney EVENTS AND THEIR TYPES

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vladikk doit-intl.com #ndcsydney EVENT: CONTRACT FOR INTEGRATING SYSTEMS

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vladikk doit-intl.com #ndcsydney { “type”: “presentation-started”, “timestamp”: 1556969773, “createdBy”: 12, “payload” : { … } }

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vladikk doit-intl.com #ndcsydney TYPES OF EVENTS Event Notification Event-Carried State Transfer Event Sourcing / Domain Event

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vladikk doit-intl.com #ndcsydney EVENT NOTIFICATION Something important No (direct) response Minimal informaAon

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vladikk doit-intl.com #ndcsydney EVENT NOTIFICATION

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vladikk doit-intl.com #ndcsydney TYPES OF EVENTS Event Notification Event-Carried State Transfer Event Sourcing / Domain Event

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vladikk doit-intl.com #ndcsydney { “customerId”: “123”, “name”: “John Johnson”, “state”: “approved”, … }

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vladikk doit-intl.com #ndcsydney TYPES OF EVENTS Event Notification Event-Carried State Transfer Event Sourcing / Domain Event

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vladikk doit-intl.com #ndcsydney EVENT SOURCING / DOMAIN EVENTS Events are the source of truth CombinaAon of noAficaAon and state transfer “Immutable, stateless, truthful”

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vladikk doit-intl.com #ndcsydney EVENT SOURCING / DOMAIN EVENTS

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vladikk doit-intl.com #ndcsydney TYPES OF EVENTS Notification Event:
 { “type”: “Marriage”, … }
 Event-Carried State Transfer { “type”: “PersonalDetailsChanged”, “newLastName”: “johnson” } Domain Event: { “type”: “GotMarried”, “partnerId”: “TZ7138821”, “assumedPartnersLastName”: true }

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vladikk doit-intl.com #ndcsydney STORIES OF WAR AND HORROR

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vladikk doit-intl.com #ndcsydney

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vladikk doit-intl.com #ndcsydney FROM MONOLITH TO MICROLITHS 01

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vladikk doit-intl.com #ndcsydney Monolith Everything

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vladikk doit-intl.com #ndcsydney Marketing CRM BI Clients Notification Event

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vladikk doit-intl.com #ndcsydney Marketing CRM BI Clients Notification Event Calculate Metrics

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vladikk doit-intl.com #ndcsydney Marketing CRM BI Clients Notification Event Calculate Metrics Logical Coupling

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vladikk doit-intl.com #ndcsydney Marketing CRM BI Clients Notification Event Calculate Metrics Logical Coupling Transactional Coupling

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vladikk doit-intl.com #ndcsydney Marketing CRM BI Clients Domain Event Event Sourcing

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vladikk doit-intl.com #ndcsydney Marketing CRM BI Clients Domain Event Event Sourcing

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vladikk doit-intl.com #ndcsydney COMMANDS MASQUERADING AS EVENTS 02

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vladikk doit-intl.com #ndcsydney CRM Relational Database Marketing BI Clients State

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vladikk doit-intl.com #ndcsydney CRM Event Store Sales Agent Relational Database CRM Result Command

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vladikk doit-intl.com #ndcsydney CRM Event Store Sales Agent Execution Result Command Projections

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vladikk doit-intl.com #ndcsydney COUPLED PROJECTIONS 03

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vladikk doit-intl.com #ndcsydney Event Store Domain Events BI Search Indexes Materialized Views (UI) State Projections

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vladikk doit-intl.com #ndcsydney Event Store Domain Events BI Search Indexes Materialized Views (UI) Duplicated Logic Logical Coupling

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vladikk doit-intl.com #ndcsydney Event Store Many Types of Events!!! BI Search Indexes Materialized Views (UI) Duplicated Logic Logical Coupling Implementation Coupling

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vladikk doit-intl.com #ndcsydney Event Store State Change Notification BI Search Indexes Materialized Views (UI) Private Events Service Boundary State Projection

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vladikk doit-intl.com #ndcsydney ARCHITECTURAL TROJAN HORSE 04

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vladikk doit-intl.com #ndcsydney Microservice A Microservice B Microservice C Microservice D

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vladikk doit-intl.com #ndcsydney Microservice A Microservice B Microservice C Microservice D New
 Microservice

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vladikk doit-intl.com #ndcsydney Microservice A Microservice B Microservice C Microservice D Implementation Coupling

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vladikk doit-intl.com #ndcsydney Microservice A Microservice B Microservice C Microservice D Anti-Corruption Layer New
 Microservice Model Transformation Business Complexity

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vladikk doit-intl.com #ndcsydney DISTRIBUTED MONOLITH 05

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vladikk doit-intl.com #ndcsydney Microservice A Microservice B Microservice C Microservice D

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vladikk doit-intl.com #ndcsydney Microservice A Microservice B Microservice C Microservice D

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vladikk doit-intl.com #ndcsydney Microservice A Microservice B Microservice C Microservice D

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vladikk doit-intl.com #ndcsydney OPTIMISTIC CONSISTENCY 06

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vladikk doit-intl.com #ndcsydney System DB User Message Bus Backup DB Cached State Analysis Model Enriched From

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vladikk doit-intl.com #ndcsydney System DB User Message Bus Same “Transaction” Backup DB Cached State Analysis Model Enriched From Transactional Coupling

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vladikk doit-intl.com #ndcsydney System DB User Message Bus Same “Transaction” Backup DB Cached State Analysis Model Enriched From Transactional Coupling Transactional Coupling

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vladikk doit-intl.com #ndcsydney System DB User Message Bus Same “Transaction” Backup DB Cached State Analysis Model Enriched From Transactional Coupling Transactional Coupling Temporal Coupling

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vladikk doit-intl.com #ndcsydney System DB Message Bus Backup DB Cached State Analysis Model OUTBOX PATTERN

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vladikk doit-intl.com #ndcsydney LESSONS LEARNED

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vladikk doit-intl.com #ndcsydney BE PESSIMISTIC

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vladikk doit-intl.com #ndcsydney BE PESSIMISTIC System DB Backup DB Analysis Model Cached State

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vladikk doit-intl.com #ndcsydney BE PESSIMISTIC Assume that everything will fail Event-Driven Architecture - The “driven” part is there for a reason Ensure delivery of events no matter what

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vladikk doit-intl.com #ndcsydney PRIVATE / PUBLIC EVENTS Event Store BI Search Indexes Materialized Views (UI) State Projection

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vladikk doit-intl.com #ndcsydney PRIVATE / PUBLIC EVENTS Private events - Implementation details. Public events - Public API. Should be stable. Use public events to “compress” private events.

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vladikk doit-intl.com #ndcsydney EVALUATE SERVICES’ CONSISTENCY REQUIREMENTS Eventual consistency? - Event-Carried State Transfer Read last write? - Notification Event + API for getting up-to-date data Concurrency control? - Merge them ASAP!

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vladikk doit-intl.com #ndcsydney EVALUATE SERVICES’ CONSISTENCY REQUIREMENTS Eventual consistency? - Event-Carried State Transfer Read last write? - Notification Event + API for getting up-to-date data Concurrency control? - Merge them ASAP!

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vladikk doit-intl.com #ndcsydney Be pessimistic Use private and public events Evaluate consistency requirements LESSONS LEARNED

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vladikk doit-intl.com #ndcsydney WRAP UP

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vladikk doit-intl.com #ndcsydney Manages complexity Local complexity - complexity of a system’s component Global complexity - interconnectedness between components SOFTWARE ARCHITECTURE

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vladikk doit-intl.com #ndcsydney Notification Event - something interesting happened Event-Carried State Transfer - publishing changes in data Domain Events - immutable, truthful, stateless TYPES OF EVENTS

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vladikk doit-intl.com #ndcsydney Be pessimistic Use private and public events Evaluate consistency requirements LESSONS LEARNED

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https://bit.ly/2ptJ5fS THANK YOU! @vladikk vladikk.com https://bit.ly/31nSD9c http://careers.doit-intl.com