Leveraging the
power of Reactive
Architectures
Microservices, Reactive and Distributed Systems Vienna
Vienna, August 2021
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@duffleit
@duffleit
david.leitner@squer.at
David Leitner
Coding Architect
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Reactive?
Programming with, or designing upon,
asynchronous data streams.
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asynchronous data streams.
Space
Time
Collections
Iterator Generator
Value
Getter Setter
Promise
Deferred Resolver
Stream
Reader Emitter
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The relationship between them is implicit, an idea that only exists in the
mind of the programmers. It should be explicit, a part of the language,
and existing for all time. Counter and doubled should be bound.
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the Destiny Operator
paulstovell.com/reactive-programming
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1
map(x => x*2) 2
3
6
Reactive Programming,
is Programming with Streams.
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No content
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C’mon, show me a
down-to-earth
example.
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YAMS — Yet Another Mail Service
NEW 2021-04-11 — An important Email
2021-04-09 — Another important Email
2021-04-08 — Do you want to join my network?
2021-04-05 — Nigerian prince wants to send you money
X
your inbox contains 4 mails
1 NEW Mail
Reload
Controller
Rest Client
update UI Element
update UI
update UI
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YAMS — Yet Another Mail Service
NEW 2021-04-11 — An important Email
2021-04-09 — Another important Email
2021-04-08 — Do you want to join my network?
2021-04-05 — Nigerian prince wants to send you money
X
your inbox contains 4 mails
1 NEW Mail
Reload Websocket Client
Email Email
count()
count()
collect()
filter()
subscribe
Email
map()
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YAMS — Yet Another Mail Service
NEW 2021-04-11 — Hello Reactive Systems Vienna! 👋
2021-04-09 — Another important Email
2021-04-08 — Do you want to join my network?
2021-04-05 — Nigerian prince wants to send you money
X
your inbox contains 5 mails
2 NEW Mail
Websocket Client
Email Email
count()
count()
collect()
filter()
subscribe
Email
NEW 2021-04-11 — An important Email
map()
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We move from a
pull-based design,
to an asynchronous
push-based design.
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Reactive Programming
Reactive Architectures
We take the same concepts from reactive programming
and move them up to the system architecture.
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“The Universal BBC Architecture”
Back in 2010…
Allard Buijze
Box Cylinder
Box
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Internet has 4.7 Billion users.
Facbook has 2.8 Billion users.
Youtube has 2.1 Billion users.
2010
2020
The Internet has 1.4 Billion users.
A single website may
now handle twice as
much traffic as the entire
internet a decade ago.
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No content
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The Reactive Manifesto
Message
Driven
Responsive
Elastic Resilient
NFR
Supported by
Enabled by
Scalability Extendibility
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Microservice A
Microservice B
Message
Driven
Responsive
Elastic Resilient
Value
Form
Means
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Microservice A
Microservice B
Message
Driven
Responsive
Elastic Resilient
Value
Form
Means
Microservice B
Microservice B
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Microservice A
Microservice B
Message
Driven
Responsive
Elastic Resilient
Value
Form
Means
Microservice B
Stream
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Microservice A
Microservice B
Message
Driven
Responsive
Elastic Resilient
Value
Form
Means
requests pile up
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Message
Driven
Responsive
Elastic Resilient
Value
Form
Means
Microservice A
Stream
Microservice B
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We support
Back-Pressure Stream
Provider Consumer
events are stored
until consumed
Stream
Provider Consumer A
Consumer C
Consumer B
scaling out
consumers
We can horizontally scale by
Location Transparency
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We move from a
synchronous pull-based
architecture, to an
asynchronous push-based
architecture.
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Push, Pull,
Whaaaaaat?
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Microservice A
Microservice B
Microservice C
Web Application
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Microservice A
Microservice B
Microservice C
Web Application
Microservice C
with high latency
First Generation
Integrated Synchronous
without Backpressure Support
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Microservice A
Microservice B
Microservice C
Web Application
Microservice C
with high latency
Second Generation
Partially Asynchronous &
Backpressure Support
Queue
isolates bottleneck
Queue
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Web Application
Stream
Microservice
usually Backend-For-Frontend (BFF)
Microservice A
Microservice B
Microservice C
Thirds Generation
Stream Centric and
Fully Asynchronous
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Events as the System State
Stream of Transactions
Max sent Tim 100€ Max sent Maria 70€ Tim sent Maria 25€
➡
Current Balance
Max
- 100€
Tim
+ 100€
Maria
+ 70€
- 170€ + 75€ + 95€
Stream-table duality
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Web Application
Stream
Microservice
usually Backend-For-Frontend (BFF)
Microservice A
Microservice B
Microservice C
Migration via
Change-Data-Capture
Legacy
Database New User Added
User Updated
Change-Data-Capture
DB Log
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www.squer.link/migration-strategies
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Events as the System State
Stream of Transactions
Max sent David 100€ Max sent Maria 70€ David sent Maria 25€
Current Balance
Max
- 100€
David
+ 100€
Maria
+ 70€
- 170€ + 75€ + 95€
Stream-table duality
the truth,
the whole truth,
nothing but the truth.
Event Souring
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Web Application
Stream
Microservice
usually Backend-For-Frontend (BFF)
Microservice A
Microservice B
Microservice C
Thirds Generation
Stream Centric and
Fully Asynchronous
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Web Application
Eventstore
Microservice
usually Backend-For-Frontend (BFF)
Microservice A
Microservice B
Microservice C
Thirds Generation
Stream Centric and
Fully Asynchronous
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Web Application
Eventstore
Microservice
usually Backend-For-Frontend (BFF)
Lambda A
Lambda B
Lambda C
Thirds Generation
Stream Centric and
Fully Asynchronous
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Web Application
Stream
Microservice
usually Backend-For-Frontend (BFF)
Microservice A
Microservice B
Microservice C
Thirds Generation
Stream Centric and
Fully Asynchronous
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Stream Centric Systems
are the only way to build
autonomous Microservices.
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by: twitter.com/swardley
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Stream Centric Systems
are the only way to build
autonomous Microservices.
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Microservice A
Microservice B
Microservice C
UI
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Account Summary Service
Transaction Service
User Service
Web Banking
Categorization Service
Config Service
The rise of the
Entity Service
Antipattern
High Presure
Low Resilience
Z
Y
X
Payment Service
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Account Summary Journey
Transaction Service
User Service
Web Banking
Categorization Service
Config Service
The rise of the
Entity Service
Antipattern
High Presure
Low Resilience
Z
Y
X
Payment Journey
Paymet Customer Journeys
Account Overview Customer Journeys
Low service Autonomy
Weak Independent Deployability
Weak Independent Scalability
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Account Summary Journey
Transaction Service
User Service
Web Banking
Categorization Service
Config Service
Payment Journey
projection
projection
We never write to projections,
we only read from them.
CQRS in a nutshell
websockets
Strong Service Autonomy at Runtime
Smaller Deployment Footprint
Good Horizontal Scalability
Account Summary Journey
projection
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Lambda A
Web Application
Lambda B
Lambda C
Stream
GraphQL
Microservice A
Microservice B
Microservice C
Web Application
➡
pull-based push-based
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www.squer.at
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Focus on Realtime Integration
Insurance
Calculation
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GraphQL
Step 1 Step 2 Step 2
Car Brand
Build Year
Car Model
Insurance Agent
Customer
✅ This Is Correct
Alfa Romeo Giulia, 2020
110PS, Diesel
Products
Users
Configurations
Eventstore
GraphQL
car brand has changed
Alfa Romeo
2020
Giulia, 110PS
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GraphQL
Step 1 Step 2 Step 2
Car Brand
Build Year
Car Model
Insurance Agent
Alfa Romoe
2020
Giulia, 110PS
Customer
✅ This Is Correct
Alfa Romeo Giulia, 2020
110PS, Diesel
Step 1 Step 2 Step 2
Coverage
200 €
🏁 Sign Digital
Do you accept 70% coverage
for 200€?
Products
Users
Configurations
Eventstore
GraphQL
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GraphQL
Step 1 Step 2 Step 2
Car Brand
Build Year
Car Model
Insurance Agent
Customer
✅ This Is Correct
Alfra Romeo Giulia, 2020
110PS, Diesel
Step 1 Step 2 Step 2
Coverage
250 €
🏁 Sign Digital
Do you accept 90% coverage
for 250€?
Products
Users
Configurations
Eventstore
GraphQL
Customers expect
realtime syncronisation
between channels.
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Focus on Resilience
High
Available
Banking
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Mobile Banking Usage
Show balance & last transactions: 93%
Initiate new payment: 3%
Any other functionality: 4%
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Transactions
Web Banking
Users
Accounts
Stream
GraphQL
Projection
Projections
1⃣ Projections act as read-models for a specific client.
2⃣ They subscribe to events & hydrate the projection.
3⃣ The client only reads from the projection.
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Transactions
Web Banking
Users
Accounts
Stream
GraphQL
Projection
Projections
1⃣ Projections act as read-models for a specific client.
2⃣ They subscribe to events & hydrate the projection.
3⃣ The client only reads from the projection.
Projection
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GraphQL
Mobile Client
Projection
Transactions
Web Banking
Users
Accounts
Stream
GraphQL
Projection
Projections
1⃣ Projections act as read-models for a specific client.
2⃣ They subscribe to events & hydrate the projection.
3⃣ The client only reads from the projection.
Only one hard problem in
computer science left. 😎
Projection
Show balance & last transactions working,
93% of customers still happy.
With a concept like
optimistic UIs even more.
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lousy memes
Ok let‘s
sum up!
lousy memes
within lousy
memes
High Resilience &
Scalability
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Architectural Styles always
buy you options.
This stuff is cool,
Reactive Architectures buy you Resilience,
Realtime Capabilities, Elasticity, & Extendibility.
you pay by complexity.
💵
e.g. perpetual, or eventual inconsistency
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Maybe start small,
and shift to reactive systems once needed.
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by: twitter.com/swardley
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@duffleit
@duffleit
david.leitner@squer.at
David Leitner
Coding Architect
squer.at/slides
this presentation