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Mastering Akka

Mastering Akka

By : Baxter
3.7 (6)
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Mastering Akka

Mastering Akka

3.7 (6)
By: Baxter

Overview of this book

For a programmer, writing multi-threaded applications is critical as it is important to break large tasks into smaller ones and run them simultaneously. Akka is a distributed computing toolkit that uses the abstraction of the Actor model, enabling developers to build correct, concurrent, and distributed applications using Java and Scala with ease. The book begins with a quick introduction that simplifies concurrent programming with actors. We then proceed to master all aspects of domain-driven design. We’ll teach you how to scale out with Akka Remoting/Clustering. Finally, we introduce Conductr as a means to deploy to and manage microservices across a cluster.
Table of Contents (11 chapters)
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CQRS in the event sourced world


We know from our work in Chapter 4, Making History with Event Sourcing, that an event-sourced app is all about commands (actions) and events (reactions to those commands). The events that are generated from these commands are used to represent the state of a given entity over time, with the past events being replayed whenever the current state of an entity is needed. The storage model itself does not store the current state, only the occurrences that lead to a current state for a particular entity.

Given this model, what can I do if I want to query for a particular entity that has the current state with a field matching a specified value? If I don't store the current state, how can I answer this question? Will I have to read every entity in the system, replay its event stream to get its current state, and then see if it's a match? An approach like that will not be tenable, so let's not even consider it.

One answer to this question is to consider commands and...

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