Questions tagged [event]
The event tag has no usage guidance.
96
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Kafka : Is sending some payload data (identifier) in headers considered a good practive?
I am wondering about some architectonical decisions in our system.
There are situations where we are sending import business events through kafka which should be performed in every case.
All the cases ...
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184
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How to propagate seldomly changing data in a distributed system
We store data – some kind of metadata like car manufacturers or types of computer parts – in one of our applications.
This data changes rarely. Let's say it changes once every two weeks.
This data is ...
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148
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Is this a good use of events?
At my company we are revising some backend architecture. I think I have identified a use case where event streaming (for example with Apache Kafka or RabbitMQ) makes sense.
Because me (and everyone ...
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76
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How to define the data model in an event-based infrastructure
After my team went all-out on the microservice paradigm with an emphasis on message passing, I'm having trouble defining and keeping track of all the events in the system.
I've read some guides on the ...
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63
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How do I design an event bus to both publish and consume events to an external message broker
I have an application that needs to publish events to an event broker and consume events from the event broker.
I want to do this with an event bus. This event bus should have one public method: ...
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47
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Dispatching an event in the decorator or use some other design pattern entirely?
Disclaimer: before explaining the problem here I am aware that the answer to the question might be a subject of an opinion. The reason I am asking this question is because I still believe that there ...
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294
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How do event sourcing services recreate the state of an entity?
I'm reading about event sourcing and have a question regarding the recreation of an entity state.
For a simple scenario, lets say we have Order events such as OrderCreated / OrderUpdated / ...
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2k
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Event bus vs PubSub
I have been using queues and PubSub patterns for years but never really came across the terminology "event bus". After some googling I didn't really find a clear distinction between "...
- 149
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257
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Should I send the current or previous state with my state changed event?
I have an event that is raised when my job objects change state (e.g. initializing, running, complete, etc). The event is to be invoked from my set method in the State property, but before I make it ...
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How do desktop applications get notified of events over the internet?
I would like to display something on my desktop by tapping a button on my mobile app.
For example, there is a "show cat" button on my mobile app. When I tap that button, a new window should ...
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4
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715
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C# How to avoid memory leak in this case
I've got a Window, which gets a viewmodel instance injected into its constructor.
The window sets its DataContext to that viewmodel.
The viewmodel contains a command to "submit" the window ...
- 291
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155
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Scaled services and order of events sent as messages (using a broker)
How would you go about making sure that "events" sent as messages to any sort of broker (Kafka, RabbitMQ etc) from multiple instances of the same service (load balanced) are actually added ...
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61
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Long-running jobs in an event-driven environment with constrained max-execution-duration
Hello we have an async event-driven system (kotlin, spring cloud stream, rabbitmq) where there might be an event FooPayloadArrived, published by an ingress rest-controller.
Processing this ...
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76
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Applications interested to the same event and concurrency
I have an event pubblished in a bus(rabbit) and two application that are subscribed to this Event.
public class CreationEvent
{
public int CreationEventID {get; set; }
... other properties
}
...
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-2
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1
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51
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What is the proper diagram to describe an event subscriber final graph?
I'm working on a microservice application and I need to describe the complete execution graph of a specific event being published, where each node in the graph is a specific microservice subscription ...
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185
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Coping with lack of infinite retention event broker in event driven architecture
I am reading “Building Event Driven Microservices”.
It states a requirement of the event broker is:
Infinite retention: Event streams must be able to retain events for an infinite period of time. ...
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258
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Ingest data from our partener : API POST vs Event Driven Architecture
I am in the process of carrying out a software architecture for my client, in fact
THE HISTORY OF THE REQUIREMENT :
MY PARTNER SEND cvs files via MFT to MY CLIENT , many times a day .
MY CLIENT has a ...
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146
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Eventing: Determine if Set of Messages has been Processed
Given a Set of messages sent to a Queue, what are good ways to determine all of the messages have been processed?
Constraints:
Large number of messages
Other messages besides those in the Set will be ...
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666
views
How to represent a loop in Event Storming?
I recently ran an Event Storming session and a scenario came up where we needed to represent a loop within the process. The events and commands needed to happen iteratively until a condition is meant ...
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141
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How to deal with massively concurrent events?
I got the following interview question:
Say the company has this event, where we will create a button on a website and only the first ten clicks will be accepted and win a prize. Assume that there a ...
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184
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What are the best way to publish application event in a spring boot application?
My goal is to collect/publish different types of information from the application. We use Kafka for the event bus. Consider the following sample code.
class UserService {
public User ...
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103
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How to subscribe to collection edits happening in a different thread?
I'll be using C# for my example since this is what I am using, but the problem is sort of generic.
My app code takes a collection of Foos (externally populated and edited) to do some processing, and ...
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3
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1k
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How to handle data inconsistency in microservice architecture?
Let's assume we have two services - user and auth with a message broker in between. user service handles CRUD action on user entity and auth service handles authentication. When a user is created/...
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314
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How to create an Event-Driven Architecture with many external sources
I work for this Accounting company - as a Product Owner - that uses several external services (one for Contract management, another one for Accounting Demands management, a third one for Financial ...
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74
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Experiences with coarse grained and fine grained message designs in an ECST pattern
I am currently facing a dilemma in the design of a message oriented distributed system following an Event Carried State Transfer pattern. This is essentially a "near real time ETL" used to ...
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104
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Ops in event-driven paradigm
TL;DR event-driven system seems to focus on a highlevel view of the system ("error rate is 0.5%"). How are IT operations supposed to locate and remedy individual issues in such systems?
In ...
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217
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WPF MVVM EventAggregator Cons?
We have a wpf mvvm application with a lot of "panes". Just like the draggable panes in visual studio for example.
All of these are individual usercontrols with their own viewmodels and im trying to ...
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2k
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When to publish domain events when handling transactions in the application service
This is something that has been bothering me for quite some time, I tried different approaches over the past year but I always come back to reflect on this, so I'll throw myself out here !
So, first ...
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358
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Message bus: should an event handler trigger other commands?
Given I have a message bus that can handle commands and events. A command handler can dispatch an event. But should an event handler be able to dispatch another command? Or should event handlers only ...
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83
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How to call the API once per event-message?
I have X number of servers in NLB listening to an event that gets published by a backend system.
I am planning to develop a windows service that listens to the event and then calls an internal API. ...
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247
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How to implement a chain of events on a tree's CRUD operations?
I am working on a project in which I have a tree with 4 layers and the hierarchy is like this.
Customer -> Site -> Location -> Guardroom
In DB each entity has its own table and the child ...
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5
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2k
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How to resolve cyclic dependencies in Event-driven systems?
Consider two services (bounded contexts by DDD):
Sales
Billing
Sales is responsible for creating orders and Billing for handling payments.
Sales tracks orders and Billing holds payments:
Sales ...
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63
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Remove unwanted parameter from event
I've run into a common annoyance where I'll have an event that sends a parameter, but some consumers of the event don't need the parameter at all. So I wrap it in another function that decouples the ...
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315
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What are differences in application architecture in frontend and backend applications?
I'm pretty experienced with developing both frontend as well as backend applications, with a variety of programming languages and frameworks. I know the problem space and concepts involved in both ...
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1k
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Handle failures in Event Driven Architecture
Suppose you have a bounded context with ~30 business events and, for simplicity sake, the same number of commands like ChangeUserEmailCommand -> UserEmailChangedEvent initiated from a web UI. ...
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Aggregation and storage system design for user event processing?
I have a eCommerce like system which produces 5000 user events (of different kind like product search/product view/profile view) per second
Now for reporting business users would like to view the ...
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Error handling in an event driven system
The context
I have two components A & B, which communicate through events .
Components B is responsible for long running background processes and it listens to the following event:
...
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How to send queue messages to one queue in rabbitmq?
I want to use rabbitmq to share domains events between microservices. Due to the fact that queues are round-robin, I need to define one queue per event source and event consumer.
For example, cars-ms ...
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801
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How to ensure persistence in an event-driven microservice architecture?
Right now we have a set of micro services with a client-facing gateway responsible for authentication and routing. MySQL database and RabbitMQ for the message queue. Internal services may queue up ...
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462
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How to model User behaviour that can be shared between microservices in Event Driven architecture?
I have an Event Sourced system that has 3 micro services (simplified):
User management - Registering a user, change password etc
User account - manages debiting/crediting of the user account balance
...
42
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6k
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Applicability of Single Responsibility Principle
I recently came by a seemingly trivial architectural problem. I had a simple repository in my code that was called like this (code is in C#):
var user = /* create user somehow */;
_userRepository.Add(...
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54
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Where does the responsibility for clearing higher-level caches lie in a pyrimidal calculation system with caching at multiple levels?
I'm working on system that analyses non-trivial amounts of data. The analysis is pyramidal, in that various combine to make intermediate values, which in turn combine with each other and more inputs ...
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136
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How does event.target return the DOM object?
I read through documentation and searched on google, but couldn't find a specific answer. Currently, I have an object that subscribes to a click event. I am trying to understand how a view that ...
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162
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Microservice /Soa : how to fire notification depending on the caller?
I have this two use cases in a user registration process :
Case 1 : the user register an account online and the system should send him an email notification in order to confirm that his account has ...
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2k
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How to deal with an event if the domain aggregate was not yet persisted?
When I call paid() on my aggregate it sets all the properties internally that need to be changed based on this action. But at this time the change has not been saved to the DB, so I can't reliably ...
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Publish / Subscribe Paradigm Implementation Problems
Reading the final chapter 6 of the paper "The Many Faces of Publish/Subscribe" I stumbled across:
Decoupling is a desirable property because it enforces scalability at the abstraction level,...
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897
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How can we keep sight of business flows in event driven architectures?
I am planning to set up an event driven architecture using Spring Boot apps that publish and read messages from a Kafka broker.
Let's suppose it were an e-commerce application with the usual events (...
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236
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How are new bounded contexts deployed, and bugs fixed, in message-driven "autonomous" microservice architectures?
I'm coming from the monolith background, using a single large relational database. From my research, many proponents of the microservice architecture favor the event-driven rather than REST driven ...
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271
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Alarming on event driven systemev
How to define overall monitoring of event-driven architecture?
Each component talk to other component via events. Consumer(s) react to events within minutes to days based on use case. Each component ...
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Designing events in an event-driven (event sourced) architecture and managing duplication
I have been creating a POC for a part of our system but I'm finding some trouble communicating some of the ideas behind it. This takes ideas from Event Sourcing and Event Driven Architecture but ...
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