SLIDE 1
WHEN MICROSERVICES MEET EVENT SOURCING
Vinicius Gomes
1
VINICIUS GOMES
Software developer at ThoughtWorks vvgomes.com/blog twitter.com/vvgomes
2
WHEN MICROSERVICES MEET EVENT SOURCING Vinicius Gomes 1 - - PowerPoint PPT Presentation
WHEN MICROSERVICES MEET EVENT SOURCING Vinicius Gomes 1 - - PowerPoint PPT Presentation
WHEN MICROSERVICES MEET EVENT SOURCING Vinicius Gomes 1 VINICIUS GOMES Software developer at ThoughtWorks vvgomes.com/blog twitter.com/vvgomes 2 AGENDA The Traditional Approach Introduction to Event Sourcing CQRS Demo Summary 3 THE
SLIDE 2
SLIDE 3
AGENDA The Traditional Approach Introduction to Event Sourcing CQRS Demo Summary
3
SLIDE 4
THE TRADITIONAL APPROACH
4
SLIDE 5
EXAMPLE
Online Restaurant
5
SLIDE 6
ONLINE RESTAURANT
Data Model
6
SLIDE 7
ONLINE RESTAURANT
Services
7
SLIDE 8
Restaurant
ONLINE RESTAURANT
8
📲
POST G E T
I want to
- pen an order!
200 ✔
SLIDE 9
Restaurant
ONLINE RESTAURANT
9
📲
POST GET
I want to add an item to my order!
200 ✔
SLIDE 10
THE TRADITIONAL APPROACH
- Simple to implement
- Technology agnostic
10
GET POST PUT DELETE
SLIDE 11
CHALLENGES
11
SLIDE 12
CHALLENGES
Coupling
12
SLIDE 13
CHALLENGES
Coupling Resilience
13
Restaurant
📲
POST GET
I want to add an item to my order!
503👏
SLIDE 14
CHALLENGES
Coupling Resilience Response time
14
SLIDE 15
CHALLENGES
Coupling Resilience Response time User intent
15
POST /orders/8659a0d6/items/
Add item to order
SLIDE 16
CHALLENGES
Coupling Resilience Response time User intent Current / mutable state
16
{ "id": “6a208c41…”, "status": "OPEN", "items": [ { "id": “be596c8e…”, "quantity": 1 }, { "id": “5d09509c…”, "quantity": 2 }, { "id": “cc52d1b6…”, "quantity": 1 } ] }
SLIDE 17
EVENT SOURCING
17
SLIDE 18
EVENT SOURCING
18
SLIDE 19
DOMAIN EVENTS
19
{ "payload": { "orderId": “be596c8e…”, "itemId": “5d09509c…”, "quantity": 1 }, "payloadType": “com.restaurant.ItemAddedToOrderEvent”, "timestamp": “2017-03-25 08:48:51 -03:00”, "revision": “2”, "aggregateId": “6a208c41…” }
Model the past Immutable Permanent
SLIDE 20
EVENT STORE
Append only Sequential Long-lived
20
SLIDE 21
AGGREGATES
21
state = reduce(handle, {}, events)
Reducer function
Reducing events into state
SLIDE 22
AGGREGATES
Example
22
{ }
SLIDE 23
AGGREGATES
Example
23
payload: { id: “42” }
{ "id": “42”, "status": "OPEN", "items": [ ] }
SLIDE 24
AGGREGATES
Example
24
{ "id": “42”, "status": "OPEN", "items": [ { "id": “43”, “quantity": 1 } ] }
payload: {
- rderId: “42”,
itemId: “43”, quantity: 1 }
SLIDE 25
payload: {
- rderId: “42”,
itemId: “44”, quantity: 2 }
AGGREGATES
Example
25
{ "id": “42”, "status": "OPEN", "items": [ { "id": “43”, “quantity": 1 }, { "id": “44”, “quantity": 2 } ] }
SLIDE 26
AGGREGATES
Example
26
{ "id": “42”, "status": "OPEN", "items": [ { "id": “44”, “quantity": 2 } ] }
payload: {
- rderId: “42”,
itemId: “43” }
SLIDE 27
AGGREGATES
Example
27
{ "id": “42”, "status": "PLACED", "items": [ { "id": “44”, “quantity": 2 } ] }
payload: {
- rderId: “42”
}
SLIDE 28
AGGREGATES
Example
28
{ "id": “42”, "status": "PLACED", "items": [ { "id": “44”, “quantity": 2 } ] }
Order Aggregate
SLIDE 29
COMMANDS
29
Add item to order
{ "type": “com.restaurant.AddItemToOrderCommand”, "payload": { "orderId": “be596c8e…”, "itemId": “5d09509c…”, "quantity": 1 }, "timestamp": “2017-03-25 08:48:51 -03:00” }
SLIDE 30
COMMANDS
30
(state, command) -> [event]
Handling a command
SLIDE 31
COMMANDS
31
How do clients send commands?
📲
I want to add an item to my order!
?
SLIDE 32
COMMANDS
32
Reviewing REST
Resource Collection
host/api/orders
SLIDE 33
COMMANDS
33
Reviewing REST
Resource
host/api/orders/8659a0d6
SLIDE 34
COMMANDS
34
Reviewing REST
Nested Resource
host/api/orders/8659a0d6/items/5d1a8457
SLIDE 35
COMMANDS
35
Reviewing REST
HTTP Methods
GET POST PUT/PATCH DELETE
SLIDE 36
COMMANDS
36
Reviewing REST
Hypermedia Formats
SLIDE 37
COMMANDS
37
Commands can be resources
SLIDE 38
COMMANDS
Option #1 Generic “Commands” nested-resource
38
POST /orders/8659a0d6/commands
{ “type": “AddItemToOrderCommand”, "menuItem": “/menu/items/8d30d99“, “quantity": 2 }
SLIDE 39
COMMANDS
Option #2 Command URI
39
POST /orders/8659a0d6/items/commands/add
{ "menuItem": “/menu/items/8d30d99“, “quantity": 2 }
SLIDE 40
COMMANDS
Command discoverability
40
SLIDE 41
EVENT SOURCING
41
SLIDE 42
42
Queries?
SLIDE 43
QUERIES
Bad news 😕 The Event Store is not good for queries
43
Most applications
- A few writes
- A lot of reads
SLIDE 44
CQRS
44
SLIDE 45
CQRS
Command Query Responsibility Segregation
45
Write ✍ Read 📗
SLIDE 46
Service
CQRS
46
📲
Command Query Publish L i s t e n
SLIDE 47
Service A
CQRS
47
Service B
SLIDE 48
CQRS
48
Command model
- Command definitions
- Event definitions
- The aggregate
- Aggregate repository
- Write only API
Query model
- Event listeners
- Query entities
- Repositories
- Read only API
SLIDE 49
DEMO
49
SLIDE 50
DEMO
Online Restaurant
50
Service
SLIDE 51
DEMO
Online Restaurant
51
SLIDE 52
EXAMPLE: ONLINE RESTAURANT
52
Online Restaurant
Publishes Listen to
SLIDE 53
EXAMPLE: ONLINE RESTAURANT
53
Online Restaurant
Publishes Listen to P u b l i s h e s L i s t e n t
SLIDE 54
TECHNOLOGIES
Java Spring Boot Axon Framework Spring Data REST RabbitMQ
54
https://github.com/vvgomes/event-driven-restaurant
SLIDE 55
SUMMARY
55
SLIDE 56
MICROSERVICES + EVENT SOURCING Benefits
- History based queries
- Audit log by design
- Immutability
- User intent
- Decoupling
- Resilience
56
Challenges
- Complexity
- Snapshots
- Upcasting
- Race conditions
- Event contracts
- Eventual consistency
SLIDE 57
WHEN MICROSERVICES MEET EVENT SOURCING
Vinicius Gomes
57