To implement most business use cases, it is required to reuse existing services. Writing everything from scratch isn’t practical or efficient. A composite service is a coarse-grained service which reuses the functionality exposed by other services. This session will explore how implementing composite services using Ballerina is straightforward as it has all the features required to implement various types of composite services.

1. Senior Technical Lead, WSO2
Creating Composite Services Using
Ballerina
Isuru Udana

2. • Atomic
– Indivisible, fine-grained, no reuse of other services
• Composite
– Divisible, coarse-grained, reusing other services
Services

3. • Most real-world business use cases cannot be
satisfied with atomic services
• Reuse of existing services
Why Composite Services?

4. Healthcare Service Chaining
Real-World Scenarios

5. Composite Services in MSA
5

6. Microservices Layered Architecture
Consumer 1
API Service 1 API Service 2 API Service 3 API Service 4
Consumers
Consumer 2 Consumer 3
Service 6 Service 7 Service 8 Service 9
Service 1 Service 2 Service 3 Service 4 Service 5 Proprietary &
Legacy
Systems
Web API /
SaaS
API Services/
Edge Services
Composite Service/
Integration Services
Core Services/
Atomic Services

7. Microservices Layered Architecture
Core/Atomic Microservices
• Fine-grained self-contained services

8. Microservices Layered Architecture
Composite Microservices
• ESB in SOA => Composite Microservices in MSA

9. Building Composite Microservices
Frameworks Based on General Purpose Languages
• Not designed with suitable abstractions for network
interactions
• Developers spend more time on building service
interactions

10. Building Composite Microservices
Conventional ESBs
• ESB architecture not fully compatible with MSA
principles

11. The Solution is Ballerina!
11

12. Ballerina
• Parallel programming language for networked
applications
• Designed for network interactions with JSON/XML/SQL
and HTTP/JMS/File/WebSockets
• Serverless and container friendly

13. Building Composite Services with
Ballerina
Key Functionality
• Transformation
• Routing
• Parallel processing

14. Transformation

15. Transformation
Transformation
Logic
Structs

16. Transformation
Transform
Operation

17. Transformation Source
Target
Mapping
Operators

18. Routing

19. Routing
Content Based
Get Payload
Routing
Logic

20. Routing
Header Based
Routing
Logic
Get
Header

21. Parallel Processing

22. Parallel Processing
Workers

23. Parallel Processing
Workers

24. Building Composite Services with
Ballerina
Services
• Simple Atomic Service
• Composite Services
– Simple composite service
– Service chaining
– Service orchestration

25. Simple Atomic Service Service
Annotations
Protocol
Resource
Resource
Annotations

26. Simple Atomic Service
Protocol
Resource
Resource
Annotations

27. Simple Composite Service

28. Simple Composite Service
Logic
Downstream
Services

29. Simple Composite Service
Downstream
Services
Logic

30. Service Chaining

31. Service Chaining
Invoke
Service1
Invoke
Service2

32. Service Chaining
Invoke
Service1
Invoke
Service2
Construct
Payload
Construct
Payload

33. Service Chaining
Construct
Payload
Invoke
Service 1

34. Service Chaining
Construct
Payload
Invoke
Service 2

35. Service Orchestration Scenario
Online Vehicle Revenue License Service
Can be invoked
at the
same time

36. Service Structure
Service Path
Certificate
Validation
Resource
License
Resource
Resource Path

37. License Resource
Validate
Certs
Do
Payment
Call License
Issuer
Respond

38. Certificate Validation Function
Workers
Fork
Join

39. Certificate Validation Function
Workers
Multiple
Return
Values

40. Certificate Validation Function
Workers

41. Certificate Validation Function
Validation
Logic Multiple
Return
Values

42. Function Invocation
Function
Invocation
Function
Invocation

43. Function Invocation
Multiple
Return
Values
Function
Invocation

44. License Resource
Validate
Certs
Do
Payment
Call License
Issuer
Respond

45. Build Payment Request

46. Invoke Payment Service

47. License Resource
Validate
Certs
Do
Payment
Call License
Issuer
Respond

48. Invoke License Issuer Service

49. License Resource
Validate
Certs
Do
Payment
Call License
Issuer
Respond

50. Respond to Client

51. Conclusion
● Introduction to composite services
● Composite services in Microservices architecture
● Building Composite Services with Ballerina

52. wso2.com
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