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Event Sourcing RubySPBConf 2k18
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Anton Davydov
June 10, 2018
Programming
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190
Event Sourcing RubySPBConf 2k18
Anton Davydov
June 10, 2018
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Transcript
->
[email protected]
title: SPBRuby2k18
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@palkan_tula
me
What I learned in Japan?
Ruby is still dying language
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Java is popular
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Pascal is popular too
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Best shell ever
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❤ Руддщ ЫЗИ! ❤
❤ Hello SPB! ❤
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Anton Davydov github.com/davydovanton twitter.com/anton_davydov davydovanton.com
• Software developer at Hippo • Hanami core developer •
OpenSource evangelist
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Stickers
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Part 1: Real World
DEMO
Part 2: Software
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Pros • easy for understand • easy for implement
Cons • we have only current state of the system
• impossible to understand what happened before
Sometimes we need more work for one event
Imagine what will happen if we will work only with
events?
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Congrats, you know event sourcing!
Part 3: Event Sourcing
– Event Sourcing pattern https://docs.microsoft.com/en-us/azure/architecture/patterns/event-sourcing “Instead of storing just the
current state of the data in a domain, use an append-only store to record the full series of actions taken on that data”
How to get business events?
Event Storming
DDD
Part 4: Event Store
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Can be anything
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Rules
Immutable events
Immutable everything
How to store events?
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How get current state?
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How we can improve it?
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Part 5: Conclusions
Event Sourcing pros
Easier to communicate with domain experts
• time traveling • restore a system • logging out
from box
• You don’t work with tables you work with events
• Experemental data structures • Easy to change database implementations
• Easy to add instances for service • Can be
written on any language and you can call it from any app • Persistance
event sourcing cons
• Hard for understand and complicated abstraction • Not popular
in ruby and bad tooling here • Developers need deprogramming
• Hard to get state • Hard to understand the
whole chain of events • Another architecture type with different DB structure
• Async world • Versions and versions compatibility • Updating
or deleting events • Eventual Consistency
Part 6: Usage
Simple way
gems
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github.com/zilverline/sequent
Brave way
Build all stuff by self
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hanami-events
Just pub sub transport layer with event versions and types
microservices
microservices
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How to share state across DBs?
Idea #1: send data to specific service
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Problems
One service know about data from other
1 -> N
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Idea #2: events
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Important
Make events full as you can
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Part 7: Next Steps
CQRS (Command Query Responsibility Segregation)
– Martin Fowler “You can use a different model to
update information than the model you use to read information”
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DDD
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Books
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->
[email protected]
title: SPBRuby2k18
github.com/davydovanton twitter.com/anton_davydov davydovanton.com Thank you ❤