Rethinking Reactive Architectures

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Rethinking Reactive Architectures The Cloud First Paris / Remote, March 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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Stream Caller Receiver Caller Receiver propagate change observe change trigger change directly The reactive programming paradigm is based on asynchronous streams which propagate change. This differs from imperative programming, where statements are used to change a program’s state.

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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 TheCloudFirst.io! 👋 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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Let’s talk about architecture ﬁrst, What does this term even mean? The main subsystems in a systems and how they are connected together. Perry and Wolf The shared understanding of the senior people within a project. Ralph Johnson The things that are hard to change. Martin Fowler

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What is good Architecture And how ﬁnd deﬁne it. PunchCard Talk Non Functional Requirements Those requirements which make your software non-functional if you do not consider them.

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What is good Architecture And how find define it. PunchCard Talk ILITIES of Software

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What is good Architecture And how find define it. PunchCard Talk Security Usability Consistency Availability This is your architecture. A tradeoff. Business Requirements

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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 did a decade ago.

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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

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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

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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 scale-out 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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Microservice A Microservice B Microservice C Web Application Microservice C with high latency First Generation MicroServices Synchronous and without Backpressure Support

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Microservice A Microservice B Microservice C Web Application Microservice C with high latency Second Generation MicroServices Partially asynchronous with Queues Queue isolates bottleneck Queue

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Web Application Stream Microservice usually Backend-For-Frontend (BFF) Microservice A Microservice B Microservice C Third Generation MicroServices Fully asynchronous & stream-centric

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Events as the System State Stream of Transactions Max sent David 100€ Max sent Maria 70€ David sent Maria 25€ User Balance David + 75 € Max - 170 € Maria + 95 € ➡ Event Sourcing 100% reliable audit log.

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Web Application Stream Microservice usually Backend-For-Frontend (BFF) Microservice A Microservice B Microservice C

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Web Application Eventstore Microservice usually Backend-For-Frontend (BFF) Microservice A Microservice B Microservice C

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Web Application Eventstore Microservice usually Backend-For-Frontend (BFF) Lambda A Lambda B Lambda C Forth Generation MicroServices EventSourced with FaaS

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Microservice A Web Application Microservice B Microservice C Stream Microservice often Backend-For-Frontend (BFF) HTTP Streaming Request/Response

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Lambda A Web Application Lambda B Lambda C Eventstore Microservice often Backend-For-Frontend (BFF) HTTP Streaming Request/Response

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GraphQL ✅ Consumer Driven APIs ✅ Native Schema Support ✅ Streaming Support

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Streaming with GraphQL ➡

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Lambda A Web Application Lambda B Lambda C Eventstore Microservice often Backend-For-Frontend (BFF) HTTP Streaming Request/Response

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Lambda A Web Application Lambda B Lambda C Eventstore GraphQL Streaming Request/Response

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Lambda A Web Application Lambda B Lambda C Eventstore GraphQL Microservice A Microservice B Microservice C Web Application ➡ pull-based push-based

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Realtime Insurance Calculation Real World Example

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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 200 € 🏁 Sign Digital Do you accept 70% coverage for 200€? Lambda A Lambda B Lambda C Eventstore GraphQL Customers expect realtime syncronisation between channels.

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GraphQL Step 1 Step 2 Step 2 Car Brand Build Year Car Model Lambda A Insurance Agent Lambda B Lambda C Eventstore GraphQL Customer ✅ This Is Correct Alfra Romeo Giulia, 2020 110PS, Diesel Step 1 Step 2 Step 2 Coverage 250 € 🏁 Sign Digital Do you accept full coverage for 250€?

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Resilient Banking with Projections Real World Example

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Mobile Banking Usage Show balance & last transactions: 93% Initiate new payment: 3% Any other functionality: 4%

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Microservice A Web Banking Microservice B Microservice C 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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There are only two core issues in Computer Science: • cache invalidation, • and naming things.

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There are only two core issues in Computer Science: • unused potential of reactive systems, • and naming things.

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There are only two core issues in Computer Science: • unused potential of reactive systems, • and naming things. • and off-by-one-errors.

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GraphQL Mobile Client Projection Microservice A Web Banking Microservice B Microservice C Eventstore 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. Show balance & last transactions: 93%

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The Reactive Manifesto Message Driven Responsive Elastic Resilient NFR Supported by Enabled by Scalability Extendibility

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This stuﬀ is cool, but think twice, & ensure that reactive architectures really ﬁt your problem at hand (aka. NFRs).

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Architectural Styles buy you options Reactive Architectures buy you mainly Resilience, Realtime Capabilities, Elasticity, & Extendibility. you pay by complexity. 💵

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Maybe start small, and shift to reactive systems once needed.

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@duffleit @duffleit david.leitner@squer.at David Leitner Coding Architect

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squer.link/kafka