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Practical Reactive Streams with Akka

Implement asynchronous, non-blocking reactive streams with backpressure
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  • This course will show you how to use Akka to build asynchronous, non-blocking reactive streams with back-pressure.
  • Using practical examples we'll cover both the simple API and the GraphDSL.
  • Learn how to correctly implement asynchronous boundaries, parallelism, integration with Akka Actors, and more.


This is a follow-on course to the Practical Concurrency with Akka course. You should have completed that course and be comfortable creating actors using the Akka Typed API before starting this course.

Contents - contains 8.5 hours of video - equivalent to 2 days of live training.


Having problems? check the errata for this course.


What are reactive streams?

11m 39s

Creating our first stream

A note about external sources

1m 29s

Using the Akka libraries

8m 11s

Creating a source

4m 52s

Creating a sink

3m 55s

Creating a flow

4m 20s

Building and running a graph

7m 12s

Simple Sources and Sinks

Finite Sources

6m 3s

Infinite Sources

7m 42s

Basic source operators

4m 5s

Creating sinks

2m 59s

Graph convenience methods

5m 43s

Simple Flows

Map and Filter

6m 56s


4m 12s


2m 8s

Flows of generic data types

10m 41s

Combining flows with sinks and sources

9m 20s

Exercise 1 - Big Primes


2m 42s


10m 17s

Materialized values

What are materialized values?

8m 46s

The fold method and selecting a materialized value for the graph

10m 19s

Terminating the actor system

3m 32s

The reduce method

3m 56s

Stream lifecycles

Re-using graph objects

2m 31s

Converting infinite streams to finite streams with take and limit

4m 38s

The takeWhile and takeWithin functions

5m 0s


Logging elements in a stream

9m 58s

Back pressure and graph performance

Asynchronous boundaries

10m 25s

Introducing back-pressure

5m 40s

Adding buffers to the graph

6m 28s

Other overflow strategies

3m 42s


9m 41s

Exercise 2

Instructions to create an optimised graph with a materalised value

12m 3s

The GraphDSL

Why do we need the GraphDSL?

3m 45s

Introducing the GraphDSL Syntax

5m 12s

Constructing a simple Graph using the GraphDSL

14m 20s

Understanding the Graph Construction and introducing Asynchronous Boundaries

11m 30s

Complex flow types

Introducing fan-in and fan-out shapes

3m 42s

Broadcast and merge

18m 38s

Using Balance for parallelilsm

14m 48s

Exercise 3 - implementing parallelism in GraphDSL

5m 15s

Uniform fan-in and fan-out shapes

12m 40s

Non uniform fan-in and fan-out shapes

17m 51s

Graphs with multiple sources and sinks

Combining sources with a fan-in shape

18m 20s

Sending to an interim sink with alsoTo

5m 26s

Diverting outliers to a different sink with divertTo

10m 50s

Non-runnable or partial graphs

Creating and combining open shapes

15m 20s

Using open shapes outside the graphDSL

2m 32s

Using actors in graphs

Adding an actor to our project

5m 37s

Using actors as flows

8m 38s

Using actors as sinks

7m 50s

Advanced backpressure


14m 0s

Extrapolate and expand

5m 58s

The java flow package

Java's reactive streams interfaces

17m 7s

Case Study - Blockchain mining

Introducing the case study

19m 4s

Exercise 4 - receive transactions with backpressure

5m 20s


5m 6s

Exercise 5 - mine using actors and apply the result

2m 40s


8m 5s

Creating a circular graph

18m 13s


A simple introduction to blockchains

8m 36s

Let the Course Come to You

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