Service-Oriented Architecture (SOA)

An architectural style with a focus on discrete services vs. a monolithic design.

Service — a function made available over a network to consumers.

Represents a repeatable business activity with a specific outcome.
Self-contained
Black box to consumers
Composable

Service Mesh — a conjunction of services that provide functionality akin to an application.

Services must be stateless — they must return the requested value or an exception.

SOA Roles

Service provider
Service broker / registry / repository
Service consumer

Implementation Approaches

Web Services — SOAP, REST, gRPC
Microservices
Messaging (ex: RabbitMQ)
WCF

SOA structure

App frontend
Service
- Contract
- Interface
- Implementation
  - Business logic
  - Data
Service repository
Service bus

Microservices

An architectural approach that builds an application as a series of small services that are decentralized and autonomously developed. The services are loosely coupled, independently deployable, and easily maintainable.

Characteristics:

Processes that communicate over a network via vendor-agnostic protocols.
Services organized around business capabilities.
Small; message-enabled; bound by contexts; decentralized; independently deployable.
“Do one thing and do it well.”
Lowry: “Every class is a service.”

Service granularity — defines how big a service is.

At Amazon, 1 service = 3 to 10 engineers

Service Mesh Architecture

Each service instance (SI) is paired with a reverse proxy sidecar.
SI + sidecar share a container.
Container is managed via orchestration.

Sidecar

Handles communication with other Sis
Supports service discovery
Provides load balancing
Handles authentication & authorization

Data Plane

Consists of SI + Sidecar
Handles data management, request processing and response

Control Plane

Manages interaction between services via their sidecars.

Management Plane

Lifecycle
Configuration
Performance management