size does matter - how to cut (micro-)services correctly
TRANSCRIPT
Size does(n’t) matter! How to cut a (Micro)Service correctly?
Lars Röwekamp CIO New Technologies
#wissenteilen
@mobileLarson @_openKnowledge
Microservices Monolithic Design
Microservice Design Surviving Service Design
„Monolithic Design”
What’s your problem?
‣ Building features takes too long ‣ Architectural quality has degraded ‣ Technical debt is well-known and not addressed ‣ „-ility“ problems abound ‣ Deployment is way to complicated and slow ‣ Scalability has reached its limit
‣ Replacement would be way too expensive
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„For a monolithic to change all must agree on each
change.
Each change has unanticipated effects
requiring testing beforehand.“
What’s the problem?
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Monolithic „Module“ Release
What’s the problem?
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Monolithic „Module“ Release
What’s the problem?
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Monolithic „Module“ Release
What’s the problem?
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Monolithic „Module“ Release
Scary!
What’s the problem?
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What’s the problem? You want to be here.
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Load Balancer Multi Tenancy
Mic
rose
rvic
es
What’s the problem? You want to be here.
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@Runtime@Runtim
e
a.k.
a. „
Tim
e to
Mar
ket“
What’s the problem? You want to be here.
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„Help; needed it is.”
Microservices Monolithic Design
Microservice Design Surviving Microservice Design
Kind of Definition
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„In short, the microservice architectural style is an approach to developing a single application as a suite of small services, each running in its own process and communicating with lightweight mechanisms, often an HTTP resource API.”
Martin Fowler (thoughtworks)
„As wel l as the fact that serv ices are independently deployable and scalable, each service also provides a firm module boundary, even allowing for different services to be written in different programming languages. They can also be managed by different teams.”
Martin Fowler (thoughtworks)
Microservice Design
Charakteristika
Microservices
Monolith are you kidding?
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Charakteristika
Microservice Design Conway’s Law
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Charakteristika
„Any organization that designs a system (defined broadly) will
produce a design whose structure is a copy of the organization's
communication structure.“Conway’s Law (1967)
Microservice Design
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Microservice Design
Charakteristikafree choice of languagefree choice of DB
business driven teams„DevOps“
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‣Maintainability ‣ Freedom of Evolution ‣ Replaceability ‣ Scalability ‣ Reliability & Resilience ‣ Fault Tolerance
‣ „Time to Market“
Microservice Design
Sounds great, doesn’t it!
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Microservices Monolithic Design
Service Design Surviving Service Design
Charakteristika
Surviving Service Design Microservices?
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Charakteristika
Surviving Service Design
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Charakteristika
Surviving Service Design
„For most software projects, the primary focus should be on the domain and domain logic.“
Eric Evans, 2004
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Charakteristika
Surviving Service Design
„Complex domain design should be based on a model.“
Eric Evans, 2004
Abstraction of the domain!
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Surviving Service DesignSo, what is your Domain Model?
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Surviving Service Design
Domain Model
‣ Derive Objects (names) from shared language ‣ Evolve Model with the help
of all participants
‣ BTW: Changes in language lead to changes in model
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Surviving Service Design One model to rule them all.
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Surviving Service Design
Customer
ShoppingCart
Product
Kind of BIG, isn’t it?
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„A Unit, that can be handled in all aspects
by a small Team, a.k.a. two Pizza Team”
Oliver Wegner (OTTO)
Surviving Service Design
Customer
ShoppingCart
Product
How to split?
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Surviving Service Design
Customer
ShoppingCart
Product
The challenge:
‣ Split model into smaller parts without lost of DDD benefits
Possible conflicts:
‣ „different“ models ‣ „different“ understanding
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Surviving Service Design
Customer
ShoppingCart
Product
Split strategy: „Domain objects“
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„If every Service has to be updated at the same time, it’s
not loosely coupled!”by Adrian Cockcroft (ehemals Netflix)
„If you have to know too much about the surrounding services you don’t
have a bounded context!”by Adrian Cockcroft (ehemals Netflix)
Split strategy: „Domain objects“
Surviving Service Design
Customer
ShoppingCart
Product
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Surviving Service DesignSplit strategy:
„Bounded Context“
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Charakteristika
Surviving Service Design
Bounded Context, but how?
‣ clear borders ‣ business processes ‣ avoid inconsistencies
‣ e.g. check out ‣ e.g. present product ‣ e.g. „my“ recommendations
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Charakteristika
Surviving Service Design Dependencies?
Know your Neighbors!
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Surviving Service Design Context Map
Model still consistent?
Data Owner? Data still consistent?
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„Starbucks does not use Two-Phase Commit“http://www.enterpriseintegrationpatterns.com/ramblings/18_starbucks.html
Surviving Service Design Shared Kernel
Mine? Yours?
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Surviving Service Design Shared Kernel
Versioning?
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„Be conservative in what you do, be liberal in what you expect.“
Postel’s Law (a.k.a. robustness principle)
Surviving Service Design Versioning?
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Surviving Service Design Shared Kernel
Me, too!
And me, too!I need this!
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Surviving Service Design
Customer
ShoppingCart
Product
Core Domain
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Surviving Service Design Evolution?
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Charakteristika
Surviving Service Design
http://techblog.net.lix.com/2013/01/announcing-ribbon-tying-net.lix-mid.html
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Charakteristika„A Microservice never walks alone!“
me, myself and I (2015)
Surviving Service Design
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Surviving Service Design
Bounded Context
Ubiquitous Language
names enter
Continous Integration
keep model unified by
Context Map assess/overview relationships with
Shared Kernel
Overlap allied contexts through Customer Supplier Teams relate allied contexts as
Conformist overlap unilaterally as
Open Host Service
support multiple clients through
Published Language
formalize as
Separate Ways
free teams to go
Anticorruption Layer
translate and insulate unilaterally with
#WISSENTEILENOFFENKUNDIGGUT
Surviving Service Design
Bounded Context
Ubiquitous Language
names enter
Continous Integration
keep model unified by
Context Map assess/overview relationships with
Shared Kernel
Overlap allied contexts through Customer Supplier Teams relate allied contexts as
Conformist overlap unilaterally as
Open Host Service
support multiple clients through
Published Language
formalize as
Separate Ways
free teams to go
Anticorruption Layer
translate and insulate unilaterally with
#WISSENTEILENOFFENKUNDIGGUT
Surviving Service Design
Bounded Context
Ubiquitous Language
names enter
Continous Integration
keep model unified by
Context Map assess/overview relationships with
Shared Kernel
Overlap allied contexts through Customer Supplier Teams relate allied contexts as
Conformist overlap unilaterally as
Open Host Service
support multiple clients through
Published Language
formalize as
Separate Ways
free teams to go
Anticorruption Layer
translate and insulate unilaterally with
#WISSENTEILENOFFENKUNDIGGUT
Charakteristika
Surviving Service Design Microservices?
#WISSENTEILENOFFENKUNDIGGUT
Surviving Service Design
Search
History
Recommendations
User ManagementShopping Cart
Check out!
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Surviving Service Design
Product
User ManagementShopping Cart
History
Recommendations
Product presentation!
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„Size does matter" by Lars Röwekamp (open knowledge GmbH)
Surviving Service Design
Shopping Cart
HistoryShipping
User Management
Customer Self Care!
Size does(n’t) matter A personal point of View
My point of view
‣ „Use a shared common Language“
‣ „Know your Domain Model“ ‣ „Know your Bounded Contexts“ ‣ „Know your Neighbors“
‣ „Think (also) in Processes not only in Objects“ ‣ „Be a tolerant Reader and a strict Supplier“
‣ BTW: „Talking to each other is still allowed!“#WISSENTEILENOFFENKUNDIGGUT
Charakteristika? ? ?#WISSENTEILENOFFENKUNDIGGUT
Charakteristika
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Picture Credits …
‣ #1: iStock.com / Andrew Rich (000029536120) ‣ #3: photo © Daniel Steger for openphoto.net ‣ #10: The Art of Scalability / theartofscalability.com ‣ #13: iStock.com / jpgfactory (000059091620) ‣ #15: iStock.com / VisualField (3096596) ‣ #16: Wikimedia / Webysther 20150414193208 ‣ #25: iStock.com / PeopleImages (62387488) ‣ #26: dddcommunity.org/uncategorized/about_the_cover ‣ #32: twitter.com/olliwegner ‣ #36: aws.amazon.com/de/heroes/usa/adrian-cockcroft/ ‣ #44: pixabay.com ‣ #51: techblog.netflix.com/2013/01/announcing-ribbon-tying-netflix-mid.html