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Questions tagged [event-driven-design]

Event Driven Design is the implementation of requirements through a queue of events that are triggered by user input. Callback functions only create event objects and add them to the queue so state remains unchanged.

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Event Sourcing - Replaying Events

Imagine an event sourced system where there exists a consuming service that is subscribed to a certain Event A. Once this consumer detects Event A has been emitted in the network, it handles it somehow and dispatches its own Event B. How would…
alaboudi
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CQRS projections, joining data from different aggregates via probe commands

In CQRS when we need to create a custom-tailored projections for our read-models, we usually prefer a "denormalized" projections (assume we are talking about projecting onto a DB). It is not uncommon to have the information need by the…
George
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Flink for Stateless processing

I am new to flink and our use case deals with Stateless computation. Read event, process event and persist into Database. But Flink documentation never speaks about stateless processing. Any example repository to find stateless examples or…
Forece85
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Should we store Events in a database? (Event Driven Design)

We have several services that publishes and subscribes to Domain Events. What we usually do is log events whenever we publish and log events whenever we process events. We basically use this to apply choreography pattern. We are not doing Event…
froi
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How to Implement an Event Driven State Machine in Unity?

I've implemented a simple finite state machine in Unity which I've used in a few projects, but I keep running into the same issue: how do I communicate with an object's state from an external script? Say I have a Player class that has an Idle and a…
SupriseMechanics
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Display data in the web application with Event-Driven Microservice Architecture

I am new to event-driven microservices and am interested in what is the best way to display data in a web application in such an architecture. Let say I have 2 microservices: Orders and Products with separated databases per service, and nservicebus…
Sheinar
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Why are Commands necessary in choreography-based Sagas?

One key difference often highlighted between Events and Commands in EDA is as follows: Events are something which has happened Commands are requests for something which might happen What I can't understand is why implementations often use both of…
FBryant87
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Understanding event driven architecture and state management in applications

Hello guys I have a question regarding state management in applications centered around events. Let us say take a scenario in which a some one posts a tweet on twitter, so this tweet should be visible to the users in real time. So things like…
Yashwanth somayajula
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Generic events in event driven architecture

I read some articles on event driven architecture. Every article says that generic events are bad practice. But I can imagine situations, where generic event may be handy. For example I have 3 services. Reporting service, service A and B. Service A…
bartek1965
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Event Driven Architecture on Multi-instance services

We are using microservice architecture in our project. We deploy each service to a cluster by using Kubernetes. Services are developed by using Java programming language and Spring Boot framework.Three replicas exist for each service. Services…
ugur
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Should Kafka event carried state transfer systems be implemented using a GlobalKTable for local queries?

The event carried state transfer removes the need to make remote calls to query information from other services. Let's assume a practical case: We have a customer service that publishes CustomerCreated/CustomerUpdated events to a customer Kafka…
codependent
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Choosing the right Protocol for Event Driven Architectures.

I have an app and it relies on it's Backend (Microservices architectur). I am trying to choose the right protocol and was quite inclined to choose web sockets . But since i last checked AWS API gateway doesn't support it. So that goes out of the…
Jeson Dias
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CQRS (event sourcing) reading multiple aggregates

I have 2 aggregates, which have kind of 1-to-many relationsip. For example, I have a list of questions, and I want to add some of them to questonaires, some of them are mandatory and must be added to all questionaires, some of them are not, and the…
barii
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How to trigger an action only after receiving two or more events in an event driven architecture?

I have started implementing microservices in an Event-Driven Architecture. Therefore some of my services are publishing events and listening to some other events. It is very straightforward to implement a listener when an action depends on one…
Renato Gama
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How to handle in Event Driven Microservices if the messaging queue is down?

Assume there are two services A and B, in a microservice environment. In between A and B sits a messaging queue M that is a broker. A<---->'M'<----->B The problem is what if the broker M is down? Possible Solution i can think of: Ping from Service A…
Prash
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