When you split your application into multiple module how do you make them talk to each other? How do you make them react to changes happening in other parts of the system? How do you make them tell each other that something needs to be done? When should it happen? We will have a look what we can squeeze out of domain events being published in various parts of our application and how we can use them to orchestrate a bigger business process.

1. The only reward for solving
complexity is...
… more complexity

2. Robert @Pankowecki
@arkency

3. DDD
● Bounded Contexts
● Domain Events
● Agreggates
● Entities
● Repositories
● Value Objects
● Sagas
● Read models
solving/attacking/managing
complexity

4. Bounded
Contexts

5. http://www.slideshare.net/jeppec/soa-and-event-driven-architecture-soa-20

6. http://www.slideshare.net/jeppec/soa-and-event-driven-architecture-soa-20

7. Event < Shop
Organizer, Merchant
Ticket, Product

8. User.columns.size
=> 50

9. http://www.slideshare.net/jeppec/soa-and-event-driven-architecture-soa-20

10. Message Driven Architecture
● Commands
● Events

11. Commands
module Seating
class BookEntranceCommand
attribute :booking_id,String
attribute :event_id, Integer
attribute :seats, Array[Seat]

12. class OrderShipped
SCHEMA = {
order_number: String,
customer_id: Integer,
provider: String,
delivery_id: Integer,
}
end
Events

14. Send
PDF
via
Postal
1. PostalAddedToOrder
2. PostalAddressFilledOut
3. PdfGenerated
4. PaymentPaid
5. => SendPdfViaPostal

15. Payment
paid
too
late
1. OrderPlaced
2. OrderExpired
3. PaymentPaid
4. => ReleasePayment

16. Payment
paid
OK
1. OrderPlaced
2. PaymentPaid
3. OrderDelivered
4. => CapturePayment

17. Payment
paid
OK but
delivery...
1. OrderPlaced
2. PaymentPaid
3. OrderDeliveryFailed
4. => ReleasePayment

18. Invoice
Paid
Too
Late
1. OrderPlaced
2. InvoiceIssued
3. CreditNoteIssued
4. InvoicePaid
5. OrderDelivered
6. => IssueNewInovoice

19. Discount
after 3
orders in
30 days
1. OrderShipped
2. OrderDiscountPointExpired
3. OrderShipped
4. OrderShipped
5. OrderShipped
6. => GrantDiscount

20. Trip
Booking
1. Plane Booked
2. Hotel Booked
3. Car Booking Failed
4. => Unbook Hotel
5. => Unbook Plane