Dennis van der Stelt is a software architect with almost 20 years of experience developing distributed systems. He provides coaching and training on topics like messaging concepts, architecture, and eventual consistency. His presentation covered key messaging concepts like how asynchronous messaging reduces coupling, patterns like sagas for long-running processes, and how eventual consistency is an acceptable approach for distributed systems.

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and building better & more reliable systems
Dennis van der Stelt
Software Architect
http://dennis.bloggingabout.net/
dennis@bloggingabout.net
NServiceBus Community Champ
MESSAGING
@dvdstelt
#blaak

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YOUR PRESENTER
Dennis van der Stelt
http://dennis.bloggingabout.net/
Software Architect
Professional Services
Provides coaching & training
About Dennis
Innovative software architect
Almost 20 years of experience in development of
distributed systems. Has a continuous drive to
learn and improve knowledge in different
architectural styles, including quality in software
development. Highly motivated to share his
knowledge via articles, presentations and his
blog.
Awards
NServiceBus Champ
Typemock MVP
Certified Trainer
• Presentations
• Software & Architecture audits
• SOA & Microservices advice
• Unit Testing training
• NServiceBus training

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AGENDA

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“You know nothing, Jon Snow”

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Messaging concepts
What is it about & why is it important?

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synchronous asynchronousvs

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Separation of concerns
Flexibility & Reusability
Scalability
why all the layers?

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A monolithic design is characterized by such tight coupling
among modules that they really have no independent existence.
monolithic

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MONOLITHIC DESIGN
How does my clean code become a big ball of mud?
Database

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MONOLITHIC DESIGN
How does my clean code become a big ball of mud?
Database

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COUPLING
Which layer has the
worst coupling?

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22. reduce
coupling

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SpatialTemporalPlatform
coupling aspects

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PLATFORM
Also known as ‘interoperability’
http, json, xml, xsd, etc…

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TEMPORAL
Store Front End Shipping Service

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TEMPORAL
Store Front End Shipping ServiceShipping Service

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TEMPORAL
Store Front End Shipping ServiceOrder Queue

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TEMPORAL
Store Front End Shipping ServiceOrder Queue

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TEMPORAL
Store Front End Shipping ServiceOrder Queue

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SPATIAL

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SPATIAL .net
application
.net application
ShipOrder AssignTask

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Messaging
 Reduces spatial coupling
 XML/JSON for platform coupling
 Asynchronous for temporal coupling

33. demo
Messaging using WCF

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PERFORMANCE
RPC versus Messaging

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Architecture
We do microservices, ‘cause this time
it is the silver bullet!

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SERVICE ORIENTATION AT RUNTIME

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Don’t do request/reply

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Don’t use asynchronous
messaging to query a datastore
for displaying purposes!
Everything has its place.
Messaging isn’t a silver bullet
you use for everything.

43. demo
NServiceBus Demo

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CAP Theorem
Eric Brewer, PODC Conference 2000

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CAP THEOREM
You can only pick 2

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CAP THEOREM
You can only pick 2
centralized
system
partition tolerantconsistencyavailability

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CAP THEOREM
You can only pick 2
centralized
system
partition tolerantconsistencyavailability

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CAP THEOREM
You can only pick 2
centralized
system
partition tolerantconsistencyavailability
distributed
system
partition tolerantconsistencyavailability

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CAP THEOREM
You can only pick 2
centralized
system
partition tolerantconsistencyavailability
distributed
system
partition tolerantconsistencyavailability
when there’s network partition,
which do you sacrifice?

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Match the business perspective

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But I can’t drop consistency!

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Basically Available
BASE
What is BASE?
Soft state
Eventually consistent

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Eventual Consistency
Because 100% consistency isn’t the only option

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Eventual Consistency

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Eventual Consistency

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Eventual Consistency
your “enterprise” is already eventual consistent with reality

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Eventual Consistency
your “enterprise” is already eventual consistent with reality

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“Allow things to be inconsistent and find ways to
compensate for mistakes, versus trying to prevent
mistakes altogether.”
EVENTUAL CONSISTENCY
Eric Brewer
VP of Infrastructure at Google, Professor at UC Berkeley

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Some ideas on messaging

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100% synchronized
that‘s eventual consistency.
Udi Dahanin 2010

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Sagas
Long running processes

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Death to the batchjob

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81. demo
NServiceBus Saga demo

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Asynchronous messaging helps achieve
decoupling at design- & runtime
There’s a lot to think about, designing an
eventual consistent distributed system.
Everyone needs to think about the CAP
Theorem, etc, with or without async messaging
Conclusion

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find me.
http://dennis.bloggingabout.net
dvdstelt@outlook.com