Context is King Finding Service Boundaries Derek Comartin

Context is King Finding Service Boundaries Derek Comartin @codeopinion. com

Context

What is a Service? Meaningless Term…

Tenets of SOA Service-Oriented Architecture Boundaries are Explicit Services are Autonomous Services share schema not class Services Compatibility is based on Policy

Tenets of SOA Boundaries are Explicit Capabilities Data Ownership Message Contracts

Function Behavior without Data

Database Data without Behavior

Tenets of SOA Service-Oriented Architecture Boundaries are Explicit Services are Autonomous Services share schema not class Services Compatibility is based on Policy

Tenets of SOA Services are Autonomous Self Governing Replaceable No External Dependencies

Tenets of SOA Service-Oriented Architecture Boundaries are Explicit Services are Autonomous Services share schema not class Services Compatibility is based on Policy

Tenets of SOA Share Schema not Class Message Contracts Backwards Compatibility Not tech specific

Tenets of SOA Service-Oriented Architecture Boundaries are Explicit Services are Autonomous Services share schema not class Services Compatibility is based on Policy

Tenets of SOA Service Compatibility based on Policy Constraints Security Communication

Services Boundaries Who Cares? Why do we want services boundaries?

Big Ball of Mud High Coupling

Distributed Big Ball of Mud Request/Response over HTTP

Service Self Governing Application Database

Autonomous Service Self Governing Sales Service Application Database Shipping Service Application Database

Autonomous Service Self Governing Application Database Broker

Autonomous Service Self Governing Sales Service Application Database Order Placed Event Broker Shipping Service Application Database

Little Balls of Mud Low Coupling Service A Service B Service C Event Message Broker Service D Service E

Service Counter Intuitive

Service Authority A service is the authority of a set of business capabilities.

Finding Service Boundaries How Language Context Perspective Questioning

Bounded Context Language

Bounded Context Product isn’t a Product

Bounded Context Price vs Cost Sales vs Purchasing

Finding Service Boundaries How Language Context Perspective Questioning

Bounded Context Taken out of Context If a statement or remark is quoted out of context, the circumstances in which it was said are not correctly reported, so that it seems to mean something different from the meaning that was intended.

Service Boundaries Context Matters

Finding Service Boundaries How Language Context Perspective Questioning

Service Boundaries Perspective

Service Boundaries 4+1 Architecture View Model

Finding Service Boundaries Entities Product • SKU • Name • Description • Price • Cost • Quantity

Finding Service Boundaries Entities Catalog • SKU • Name • Description • Quantity Sales • SKU • Price Purchasing • SKU • Cost

Finding Service Boundaries How Language Context Perspective Questioning

Finding Service Boundaries Right Questions Does sales need the product quantity? Catalog • SKU • Name • Description • Quantity Sales • SKU • Price Purchasing • SKU • Cost

Finding Service Boundaries Available to Promise Catalog • SKU • Name • Description Sales • SKU • Price • ATP Purchasing • SKU • Cost Warehouse • SKU • Quantity • Location

Service Boundaries Wrong Questions Is the sale price ever dictated by the product description?

Implementation Vertical Slices not Layers

Application Layers Web Framework Authorization Validation Data Access Model Database

Feature Driven Feature Model Database Feature

Single Feature Controller Authorization Validation Execution Model Database

Single Feature ASP. NET MVC Policy Auth Fluent Validation Entity Framework Model Database

Single Feature ASP. NET Core Role Auth Custom Validation Dapper Model Database

Services Service B Service A Feature Feature Model Database Feature

Pub/Sub Service A Service B Service C Event Message Topics Service D Service E

Pub/Sub Sales Invoicing Shipping Order Invoiced Message Topics Order Placed Purchasing Inventory Adjusted Warehouse Receiving

UI Composition

Finding Service Boundaries How Language Context Perspective Questioning

Finding Service Boundaries What Prefer Messaging of RPC Autonomy Data Authority

Finding Service Boundaries Resources Four Tenets of SOA http: //architectopia. blogspot. com/2008/01/four-tenets-of-soa. html 4+1 Architecture View Model https: //www. cs. ubc. ca/~gregor/teaching/papers/4+1 view-architecture. pdf Composite UIs for Microservices https: //jimmybogard. com/composite-uis-for-microservices-a-primer/

That’s it… Thanks! Derek Comartin @codeopinion. com