microservices bounded contexts and everything in … · 2020. 7. 13. · microservices bounded...

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MICROSERVICES BOUNDED CONTEXTS AND EVERYTHING IN BETWEEN


”95% of the words are spent extolling the benefits of “modularity” and that little, if anything, is said

about how to achieve it”Glenford J. Myers


“MICROSERVICES FTW!!!!!!!!1”

Me @ Internovus


“MICROSERVICES FTW!!!!!!!!1”

Me @ Internovus💩


”95% of the words are spent extolling the benefits of “modularity” and that little, if anything, is said

about how to achieve it”Glenford J. Myers


Decomposi)on Strategies

Microservices

Design Heuris)cs


INTERNOVUS

01

BUSINESS DOMAIN


Your Product Marketing Strategy

Creatives Campaigns Sales Agents

OptimizationProfits


DECOMPOSITION

02

STRATEGIES


Bounded Contexts


Domain ExpertSoftware Developer


Business Domain ExpertSoftware Developer

??? !!!

Ubiquitous Language


Campaigns Sales Agents

Your Product Marketing Strategy

Creatives

OptimizationProfits


Sales AgentCampaign Manager

??? !!!

LEAD?


Conflicting models

Different contexts

Dividing the language/model

Bounded Context


MarkeCngSales

Lead Lead

FunnelCampaign

Placement Landing PageAgency Insertion Order Message

Campaign

PropositionDesk

Conversion

ContactCDR

Bounded Contexts


MarkeCng Service

Sales Service

DecomposiCon Strategy #1: Bounded Contexts


MarkeCngSales

CommissionsDesks

Sales Optimization

CRMTelephony

Creative Catalog

Contracts

Billing

Campaign Management

Identity & Access

Ads OptimizationIdentity & Access


Business (Sub)Domains


Business Domain: Customer Acquisi)onBounded Context: Marke)ng Bounded Context: Sales

Subdomain: Crea)ve Catalog

Subdomain: Campaigns Mngmt

Subdomain: Ads Op)miza)on

Subdomain: Contracts Mngmt

Subdomain: CRM

Subdomain: Sales Op)miza)on

Subdomain: Commissions

Subdomain: Desks Mngmt


DecomposiCon Strategy #2: Subomains

Campaign Management

Service

Content Catalog Service

Desks Management

Service

CRM Service

Users Service

Billing Service


Business EnCCes and Processes


MarkeCngCreative Catalog

Contracts

Billing

Campaign Management

Identity & Access

Optimization

Campaign Management

Campaign Placement

FunnelBanner

Landing Page

WebsiteZone

Asset

Publisher

Target Market


DecomposiCon Strategy #3: EnCCes

Website Asset Target Market

Broker Distribu)on Customer


DecomposiCon Strategies

Bounded Contexts

Subdomains

Business Entities and Processes


SHOW ME THE MICROSERVICES!



Contracts

Billing

Campaign Management

Identity & Access

Optimization

Campaign Management

Campaign Placement

FunnelBanner

Landing Page

WebsiteZone

Asset

Publisher

Target Market

Campaign

Website

Placement

Funnel

Bounded Contexts? Subdomains? EnCCes?


Bounded Contexts == Microservices ?


Sales AgentCampaign Manager

??? !!!

LEAD?


MarkeCngSales

Lead Lead

FunnelCampaign

Placement Landing PageAgency Insertion Order Message

Campaign

PropositionDesk

Conversion

ContactCDR


MarkeCngSales

CommissionsDesks

Optimization

CRMTelephony

Creative Catalog

Contracts

BillingCampaign

Management

Identity & Access

OptimizationIdentity & Access

Lead

Lead



Campaign Management

OptimizationLead

Sales

Commissions

Optimization

CRM Lead

Desks

Telephony

SupportContracts

Billing

Identity & Access


Bounded Contexts Decomposi)on #1




Bounded Context

Consistency boundary of the language / model

Define the biggest valid monoliths

Required decomposition boundary


Bounded Contexts == Microservices? No


Campaign Management

Campaign Placement

FunnelBanner

Landing Page

WebsiteZone

Asset

Publisher

Target Market

Campaign

Website

Placement

Funnel


Contracts

Billing

Campaign Management

Identity & Access

Optimization

Bounded Contexts? No Subdomains? EnCCes?


MICROSERVICES

03


“A service is a unit of functionality exposed to the world” - Juval Lowy

“A mechanism to enable access to one or more capabilities, where the access is provided using a prescribed interface” - OASIS

Service


Service Interface

“Any mechanism for getting data in or out of the service”

- Randy Shoup


Service Interface

Asynchronous:

• Producing events

• Consuming events

Synchronous:

• Request / Response

• Bulk ETL


Service Interface

“Any mechanism for getting data in or out of the service”

- Randy Shoup


Service Interface


Services ➜ Microservice


A microservice is a service with a micro interface


Microservice = Microinterface

Reducing coupling between services

Limits reasons for change

Easier to understand

Better fault isolation

More autonomy between services


Microservice & Databases

Microservices should own its database

No external access

Access through Microservice’s API only

Database = infinite interface!


1 Method = Perfect Microservice !!??


STAFF ONLY

STAFF ONLY


The threshold upon which a system can be decomposed

into microservices is defined by the use cases of the

system that the microservices are a part of.


Monolith Microservices Distributed Monolith

Cost of

Change


Big Ball Of Mud Bounded Contexts

Microservices Distributed Big Ball Of Mud

Avg. Service

Size


Campaign Management

Campaign Placement

FunnelBanner

Landing Page

WebsiteZone

Asset

Publisher

Target Market

Campaign

Website

Placement

Funnel

Subdomains? EnCCes?


”Global complexity … the complexity of the

overall structure of a program or system. I.e., the

degree of association or interdependence

among the major pieces of a program”Glenford J. Myers


”Global complexity … the complexity of the

overall structure of a program or system. I.e., the

degree of association or interdependence

among the major pieces of a program”Glenford J. Myers

Composite / Structured Design, 1978


When you design a system…, then if the features can be broken into … loosely bound groups of

rela>vely closely bound features, then that division is a good thing to be made a part of the

design. This is just good engineering.

Tim Berners-LeePrinciples of design, 1998


Services + Good Engineering = Microservices


Its is not only necessary to make sure your own system is designed to be made of modular parts.

It is also necessary to realize that your own system … should always be designed to be a part

of another larger system.

Tim Berners-LeePrinciples of design, 1998


A major part of this paper will be concerned with the ques>on of how good modularity can be

achieved, that is, how modules can be chosen so as to minimize the connec5ons between them.

Barbara LiskovA design methodology for reliable soIware systems, 1972


A microservice is a service with a micro interface.

The threshold upon which a system can be decomposed

into microservices is defined by the use cases of the

system that the microservices are a part of.


A microservice is a service with a micro interface.

The threshold upon which the system can be decomposed

is defined by the use cases of the system that the

microservices are a part of.

…how to evaluate?


DESIGN

04

HEURISTICS


HeurisCc #1: Decompose to Bounded Contexts

Do not implement conflicting models in the same service. Always decompose to Bounded Contexts.


HeurisCc #2: Don’t

First Law of Distributed Object Design: “Don’t distribute your objects”

MarCn Fowler



Benefits Addi)onal Complexity


MONOLITHSYSTEM DESIGN THAT UNDERMINES DELIVERY OF FUNCTIONAL OR NON-FUNCTIONAL REQUIREMENTS



Benefits Addi)onal Complexity


Core

Supporting

Generic


Generic Subdomains

No competitive advantage

Everybody is implementing in the same way

Complex business logic


MarkeCngSales

CommissionsDesks

Optimization

CRMTelephony

Creative Catalog

Contracts

Billing

Campaign Management

Identity & Access


Generic


MarkeCngSales

CommissionsDesks

Optimization

CRMTelephony

Creative Catalog

Contracts

Billing

Campaign Management

Identity & AccessOptimization Identity & Access

Generic


MarkeCngSales

CommissionsDesks

Optimization

CRMTelephony

Creative Catalog

Contracts

Billing

Campaign Management

Identity & Access


Generic


MarkeCngSales

CommissionsDesks

Optimization

CRMTelephony

Creative Catalog

Contracts

BillingCampaign

Management

Identity & Access


Generic


MarkeCngSales

CommissionsDesks

Optimization

CRMTelephony

Creative Catalog

Contracts

Billing

Campaign Management

Identity & Access


Generic


HeurisCc #3: Buy/Adopt Generic Subdomains

Your System

3rd party product


HeurisCc #3: Buy/Adopt Generic Subdomains

Your System

3rd party product

An)-

Corr

up)o

n La

yer


Core SubdomainsInventing something new

Optimizing existing paractices

Competitive advantage


Change often


MarkeCngSales

CommissionsDesks

Sales Optimization

CRMTelephony

Creative Catalog

Contracts

Billing

Campaign Management

Identity & Access

Ad OptimizationIdentity & Access

Generic Core


Core SubdomainsInventing something new

Optimizing existing paractices

Competitive advantage


Change often


HeurisCc #4: Core Subdomains - Don’t Rush

Adhere to subdomain’s boundaries. Decompose further only when you acquire domain knowledge.


SupporCng Subdomains


Support the Core Subdomains

Can’t be bought / adopted

Simple business logic


MarkeCngSales

CommissionsDesks

Sales Optimization

CRMTelephony

Creative Catalog

Contracts

Billing

Campaign Management

Identity & Access

Ad OptimizationIdentity & Access

Generic Core Supporting


SupporCng Subdomains


Support the Core Subdomains

Can’t be bought / adopted

Simple business logic


HeurisCc #5: SupporCng Subdomains - Safe

Safe to decompose beyond the subdomain’s boundaries.


Core

Supporting

Generic


HeurisCc #6: Evaluate Consistency Requirements

Method A Method B



Concurrency control? - Same service

Method A Method B

Service A



Read last write? - Two services, synchronous communication

Service A

Method A

Service B

Method B

Sync call



Eventual consistency? - Two services, asynchronous communication

Service A

Method A

Service B

Method B

Asynchronous Communication



Concurrency control? - Same service

Read last write? - Two services, sync communication

Eventual consistency? - Two services, async communication


Service A

Method A

Service B

Method B

Asynchronous Communication


HeurisCc #7: Public / Private Events

Service

Event Type 1

Event Type 2

Event Type 3

Event Type 4

Event Type 5

Event Type 6

Event Type 1000

…



Service

Event Type 1

Event Type 2

Event Type 3

Event Type 4

Event Type 5

Event Type 6Private event types (Implementation details)}Event Type 1000

…



Service

Event Type 1

Event Type 2

Event Type 3

Event Type 4

Event Type 5

Event Type 6

Event Type 1000

…

Private event types (Implementation details)}Public event types (Public interface)}


Service

EmailChanged

PhoneNumberChanged

AddressChanged



Service

EmailChanged

PhoneNumberChanged

AddressChanged

ContactDetailsChanged



Service

EmailChanged

PhoneNumberChanged

AddressChanged

ContactDetailsChanged

Private event types (Implementation details)

} Public event type (Public interface)

}HeurisCc #7: Public / Private Events



Events?Domain Events

State Change Events

Private Public


HeurisCc #8: Make Events Explicit

Eliminate ambiguity



Service

AgentAssignedToLead



Service

AgentAssignedToLead

AgentAssignedToLead

AgentAssignedToLead



Service

AgentAssignedToLead

AgentUnassignedToLead

AgentAssignedToLead


HeurisCc #9: Evaluate Reasons for Change

Service A Service B


Same reasons for change?

Same rate of change?

Can be decoupled?

Should be the same service?

HeurisCc #9: Evaluate Reasons for Change


HeurisCc #10: Evaluate Services’ “Doors”


HeurisCc #10: Evaluate Services’ “Doors”

STAFF ONLY

STAFF ONLY


WRAP UP

05


1. A service is a unit of func)onality exposed to the world through its public interface.

2. A microservice is a service with micro interface 3. The “micro-interface” is rela)ve to the use cases of

the system that the service is a part of


Heuris)c #1: Always decompose to Bounded Contexts Heuris)c #2: Don’t go further, unless you have to Heuris)c #3: Buy/adopt generic subdomains Heuris)c #4: Core subdomains - don’t rush Heuris)c #5: Suppor)ng subdomains can be decomposed early


Heuris)c #6: Evaluate Consistency Requirements Heuris)c #7: Private / Public Events Heuris)c #8: Explicitly Define Events Heuris)c #9: Evaluate Reasons for Change Heuris)c #10: Evaluate Services’ “Doors”


Big Ball Of Mud Bounded Contexts

Microservices Distributed Big Ball Of Mud

Avg. Service

Size


Bibliography1. A Design Methodology for Reliable Soeware Systems, Barbara Liskov 2. Designing Autonomous Teams and Services, Nick Tune & Scoh Millet 3. Composite/Structured Design, Glenford Myers 4. Domain-Driven Design: Tackling Complexity in the Heart of Soeware, Eric Evans 5. Emerging Boundaries, Mathias Veraes 6. Implemen)ng Domain-Driven Design, Vaughn Vernon 7. Enterprise Integra)on Paherns, Gregory Hohpe, at al 8. Long Sad Story of Microservices, Greg Young 9. Managing Data in Microservices, Randy Shoup 10. Microservices, At Last Some Boundaries, Eric Evans 11. On the Criteria to be Used in Decomposing Systems Into Modules, David Parnas 12. Paherns of Enterprise Applica)on Architecture, Mar)n Fowler, at al 13. Principles of Design, Tim Berners-Lee 14. Programming WCF Services, Juval Lowy 15. What Every Programmer Should Know About Object Oriented Design, Melir Page-Jones

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microservices bounded contexts and everything in … · 2020. 7. 13. · microservices bounded...

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