Event sourcing
Why care?
Jakub Pilimon
ORM
STATE
STATE
new ShopItem("ordered")item.setStatus("paid")...insert into shop_items (id, status) values (1, 'ordered')update shop_items set status = 'paid' where id = 1...
"new instance of ordered Shop Item was created"
"this shop item was marked as paid"...new ItemOrdered(itemID, timestamp)
new ItemPaid(itemID, timestamp)
item.setStatus("paid")new ShopItem("ordered")new ShopItem("ordered")ordered.setStatus("paid")State 1
State 2
(State 1 + Event 2)
single ShopItem deltas
technology agnostic log, descriptive event log
@Entity
class Product {
private float price;
//...
public void cutPrice(int percent) {
checkState(percent < 100);
this.price =
price - price * percent / 100;
DomainEvents.publish(
new NewPriceAssigned(percent, this.id));
}
} def 'should cut price by 10 percent'() {
given:
ShopItem item = newWithPrice(50.00)
when:
item.cutPrice(10)
then:
item.price == 45.00
} def 'should cut price by procent'() {
given:
ShopItem item = newWithPrice(50)
when:
item.cutPrice(10)
then:
item.getUncommittedChanges() ==
[new NewPriceAssigned(price: 45)]
}QUERIES
message broker
Shop
UI
Horizontal asymmetric scaling
Failover
A/B testing
&
blue green deployments
Adding new service
Performance
Testing?
Pitfalls
Thank you!
@JakubPilimon
jakub.pilimon@gmail.com
github.com/pilloPl
Event sourcing WJUG
By Jakub Pilo
Event sourcing WJUG
Overview of event sourcing and CQRS benefits
