Server-Sent Events (SSE) is a server push technology where clients receive automatic server updates through the secure http connection. SSE can be used in apps like live stock updates, that use one way data communications and also helps to replace long polling by maintaining a single connection and keeping a continuous event stream going through it. We used a simple Kafka producer to publish messages onto Kafka topics and developed a reactive Kafka consumer by leveraging Spring Webflux to read data from Kafka topic in non-blocking manner and send data to clients that are registered with Kafka consumer without closing any http connections. This implementation allows us to send data in a fully asynchronous & non-blocking manner and allows us to handle a massive number of concurrent connections. We’ll cover: •Push data to external or internal apps in near real time •Push data onto the files and securely copy them to any cloud services •Handle multiple third-party apps integrations

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Server-Sent Events
Using Reactive Kafkaand Spring WebFlux

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GaganSolur Venkatesh
Senior Software Engineer
Chicago, USA

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Content
• What are we trying to solve?
• Options: Polling vs Websockets vs SSEs
• Spring WebFlux and Reactor Kafka
• Demo
• Questions

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• To build real-time applications we always need to consider how
we are going to send data from the server to the client.
• Two approaches are available where:
• Both the clients and the server want to send data.
• Only server want to send data to the clients.
• Use Cases:
• E-Commerce Systems (Web, Mobile, POS, Delivery)
• Live Stock Market Updates
• Live Sports Score Updates
• News Alerts
• In-app notifications
Appsthatreceiveupdatesinreal-time
What are we trying to solve?
Image: https://geekandpoke.typepad.com/geekandpoke/2009/02/before-realtime-was-born.html

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Client requests server for updates at regular intervals:
• Polling or Long Polling
ClientPull
CommonApproaches
Server pushes updates proactively to the registered or
subscribed clients:
• Web Sockets
• Server-Sent Events (SSEs)
ServerPush
Clients Server
Clients Server

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Pollingor LongPolling
ClientPull

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Web Sockets
Server Push

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Server-SentEvents(SSEs)
Server Push

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• A fully asynchronous and non-blocking reactive web stack.
• https://spring.io/reactive
Spring Web Flux
Server-Sent Events
• Reactor Kafka is a reactive API for Kafka based on Project Reactor.
• https://projectreactor.io
Reactor Kafka

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Server-Sent Events
Mom’s Pizza: Receives orders online and then pushes the orders to the stores’ POS systems.

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Demo

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Thank You
https://github.com/svgagan/kafka-summit-sse
https://medium.com/egen
gagan.solurvenkatesh@egen.solutions

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Questions?