Event sourcing (laracon online)

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Getting started with event sourcing in Laravel

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About me Freek Van der Herten Partner & developer at Spatie @freekmurze https://murze.be https://ohdear.app

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Spatie Since 2003 Websites, applications and webshops Team 9 awesome human beings Specialisation Laravel, front-end development

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Open Source   Software

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We create a lot of it ± 200 packages on Packagist ± 2,000,000 downloads a month ± 25,000,000 total downloads All Postcardware!

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Highlights Popular laravel-backup laravel-medialibrary laravel-permission New laravel-query-builder laravel-blade-x

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https://spatie.be/open-source

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https://spatie.be/open-source/postcards

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Let's talk about event sourcing

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Talk overview Projecting events in short Laravel Event Projector demo Eventsauce demo

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Event Sourcing in short

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Traditional application Write data in database An update means overwriting the old data The old data cannot be accessed anymore

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APPLICATION DATABASE TABLE value X

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APPLICATION DATABASE TABLE value X value Y

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Event Sourced Application The application will ﬁre oﬀ events Events will get written in a dedicated store Events are passed to consumers that create projections Aggregate, Aggregate Root...

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APP EVENTS Event Event 1

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APP EVENTS Event Event 1 Event 2

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APP EVENTS Event Event 1 Event 2 Event 3

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APP CONSUMER EVENTS PROJECTION Event Event 1 Event 2 Event 3

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APP CONSUMER CONSUMER 2 EVENTS PROJECTION Event Event 1 Event 2 Event 3 ANOTHER PROJECTION

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APP CONSUMER CONSUMER 2 EVENTS PROJECTION Event Event 1 Event 2 Event 3 ANOTHER PROJECTION

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APP CONSUMER CONSUMER 2 EVENTS PROJECTION Event Event 1 Event 2 Event 3 Event 4 ANOTHER PROJECTION

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Event Sourced Application Auditing requirements Extra reports needed Recording the unhappy path There is some setup required

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Laravel   Event Projector

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Laravel Event Projector Package made by Spatie It's not full event sourcing, it focuses on projections Beautifully integrated into Laravel Easy to get started with

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https://docs.spatie.be/laravel-event-projector

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Demo

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Eventsauce

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Eventsauce Package made by Frank De Jonge Focuses on aggregates Framework agnostic Separate Laravel bindings package available Very powerful, adds complexity

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https://eventsauce.io/docs/

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APP Subtract $1000

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AGGREGATE ROOT REPOSITORY UUID PAYLOAD TIME APP Subtract $1000

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AGGREGATE ROOT REPOSITORY UUID PAYLOAD TIME APP Subtract $1000 RETRIEVE Subtract $1000 AGGREGATE ROOT (empty)

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AGGREGATE ROOT REPOSITORY UUID PAYLOAD TIME APP Subtract $1000 RETRIEVE PERSIST Subtract $1000 AGGREGATE ROOT ACCOUNTS CONSUMER -$1000 ABC-123 Subtract 1000 11:12 AM (empty)

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AGGREGATE ROOT REPOSITORY UUID PAYLOAD TIME APP RETRIEVE PERSIST Subtract $750 AGGREGATE ROOT ACCOUNTS -$1000 CONSUMER ABC-123 Subtract 1000 11:12 AM Subtract $750 Subtract $1000

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AGGREGATE ROOT REPOSITORY UUID PAYLOAD TIME APP RETRIEVE PERSIST Subtract $750 AGGREGATE ROOT ACCOUNTS -$1750 CONSUMER ABC-123 Subtract 1000 11:12 AM Subtract $750 Subtract $1000 ABC-124 Subtract 750 01:17 PM

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AGGREGATE ROOT REPOSITORY UUID PAYLOAD TIME APP RETRIEVE PERSIST AGGREGATE ROOT ACCOUNTS -$1750 CONSUMER ABC-123 Subtract 1000 11:12 AM ABC-124 Subtract 750 01:17 PM Subtract $1250 Subtract $1000 Subtract $750 Subtract $1250 Propose loan

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AGGREGATE ROOT REPOSITORY ABC-123 Subtract 1000 11:12 AM ABC-124 Subtract 750 01:17 PM ABC-125 Subtract 1250, Propose loan 05:51 PM UUID PAYLOAD TIME ACCOUNTS APP CONSUMER CONSUMER 2 PROPOSED LOANS Subtract $1250 -$3000 RETRIEVE PERSIST Subtract $1000 Subtract $750 Subtract $1250 Propose loan AGGREGATE ROOT

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Demo

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In closing

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Summary Laravel Event Projector Easy to use package to get started with projections Hooks into Laravel's native events Replay capabilities No aggregates

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Summary EventSauce Framework agnostic Support for aggregates, process modelling No replay capabilities out of the box https://github.com/spatie/laravel-eventsauce

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Writes are harder, reads are easier

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Event sourcing makes the easy things harder… …and the harder things easier — Frank De Jonge

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Larabank https://github.com/spatie/larabank-traditional https://github.com/spatie/larabank-event-projector https://github.com/spatie/larabank-eventsauce

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Resources https://kickstarter.engineering/event-sourcing-made-simple-4a2625113224 https://github.com/spatie/laravel-event-projector https://github.com/eventsaucephp/eventsauce https://github.com/prooph

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Thank you! https://speakerdeck.com/freekmurze/event-sourcing-laracon-online https://spatie.be/open-source https://murze.be https://ohdear.app https://fullstackeurope.com