Questions tagged [event]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
0
votes
0answers
20 views

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 ...
1
vote
1answer
66 views

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 ...
0
votes
0answers
33 views

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 ...
2
votes
1answer
74 views

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 ...
0
votes
1answer
34 views

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 ...
-2
votes
2answers
69 views

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. ...
1
vote
1answer
37 views

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 knows its ...
2
votes
4answers
206 views

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 ...
2
votes
1answer
58 views

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 ...
0
votes
1answer
89 views

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 ...
5
votes
2answers
307 views

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. ...
2
votes
2answers
90 views

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 ...
1
vote
2answers
135 views

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: ...
0
votes
2answers
298 views

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 ...
0
votes
1answer
317 views

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 ...
4
votes
3answers
254 views

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 ...
40
votes
10answers
6k views

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(...
2
votes
1answer
49 views

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 ...
-3
votes
1answer
75 views

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 ...
0
votes
2answers
109 views

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 ...
2
votes
2answers
795 views

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 ...
1
vote
1answer
65 views

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,...
5
votes
2answers
420 views

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 (...
2
votes
3answers
161 views

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 ...
1
vote
1answer
170 views

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 ...
1
vote
2answers
1k views

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 ...
1
vote
1answer
111 views

Unit testing EventArgs - will there be timing issues?

I am writing a small game library. I capsule the logic in my model named Block. My model Block communicates only via events to it's clients (Is this a good thing to do!?). I wrote a simple unit test ...
2
votes
3answers
613 views

What should a method which creates conditionally self-unsubscribing event-handlers be named?

I develop/maintain an in-house library in a growing company with about 12 other developers that write code. This library is mostly used for scripting game behavior and we have many different projects ...
1
vote
1answer
196 views

In microservices architecture, is it reasonable that service which emits event also listens to it?

We have a complex app which built by using multiple microservices. At a runtime, one of the microservices emits an event to initialize some maintenance process in another microservices, it's ok. But ...
1
vote
2answers
274 views

Was including a keyword for events a mistake in C#?

C# has events built in with a keyword. So if you want to declare an event, you write: public event MyEventHandler SomethingHappened; It is convenient, as it does allow you to add multiple event ...
1
vote
1answer
391 views

How to write integration tests for a distributed system highly dependant on current date and flow of time?

My team and I are trying to set up some integration tests of a distributed system that is highly dependant on the flow of time and events coming from external sources. Just to give you an idea about ...
1
vote
1answer
2k views

Event Sourcing and cross Aggregate validation

I am looking into Event Sourcing (ES) and having a play around with some code Greg Young put together (Greg Young Git Repo). I like what ES offers in terms of functionality, but I am trying to apply ...
3
votes
2answers
157 views

Is avoiding raising an event when it is not needed considered premature optimisation?

I have a custom TextBox that validates its input. Whenever the validity of the input changes, a ValidityChanged event is raised and the user is informed about the validation results. My question is ...
0
votes
1answer
161 views

For what reasons would you use AngularJS expression (&) binding instead of using events?

Like the title asks, for what reasons would you use the ampersand binding in AngularJS instead of utilizing an event system--especially in a case where your application already uses events for some ...
2
votes
2answers
743 views

WPF/C#: What is the accepted way for a lower level object to notify the UI?

Setting Let's take the following example: We have a series of entertaining events on the television with each lasting only an hour and this goes on for 3 weeks. We want to create a simple App that ...
0
votes
2answers
940 views

Events fired when widgets are updated programmatically

In the GUI application I'm working on I have a number of custom (composite) widgets that I've created, with each widget having an update_gui function where I access my SQLite database so I can fill in ...
1
vote
2answers
149 views

What is 'better' - An event that tells you that something happened or accepting a delegate to be called when the event triggers internally?

I am writing a collection that accepts a time parameter, the purpose is that after that specified amount of time have passed the element won't be present in the collection. I want the user of this ...
8
votes
3answers
7k views

Should I reduce event listeners by making functions more complex?

An example would be if you had multiple inputs, each of which effect a completely different process, (perhaps one changes a div's width, while another sends ajax request for predictive search), would ...
2
votes
2answers
971 views

How chose a design for an event system

I'm working on a Entity Component System for learning purpose. I made major changes with my design so I was wondering if I could pick a better design for my event system. The purpose of the event ...
4
votes
2answers
289 views

Domain Events Grouping/Buffering

Suppose I have 3 domain events, Event1 Event2 and Event3. When command arrives at my Service Layer, I can rise 2 commands at the same time - e.g. Event1 and Event2. One Class has event listener for ...
15
votes
3answers
10k views

DDD: Where to place domain event handlers?

Could you tell me your opinion that which layer is the right one to place domain event handlers in DDD? For example, I have application service to add a new contract and I'd like to send an email ...
2
votes
1answer
367 views

Event subscription in finally clause

Background My program communicates with a device that is usually asynchronous, but can sometimes behave synchronously. I have an event handler that I use for receiving the data asynchronously, then I ...
17
votes
3answers
5k views

API Gateway (REST) + Event-Driven Microservices

I have a bunch of microservices whose functionality I expose through a REST API according to the API Gateway pattern. As these microservices are Spring Boot applications, I am using Spring AMQP to ...
-2
votes
1answer
60 views

Name for object to re-order events received in arbitrary order?

I have a program which generates events. They are ordered with a Lamport clock and sent over the network. They may arrive in a different order. On the receiving end I have an object which re-orders ...
4
votes
1answer
82 views

Using domain events to express some reached state

In general, domain events are used to make a notification, when something has happened to entity, but is it okay - from perspective of ddd - to use domain events to make a notification, when entity ...
3
votes
2answers
2k views

What does “initialize event handler” mean in this context?

In file1.js I read: // NOTE: initialize your app event handlers here, see file2.js for a simple event handler example // TODO: configure following to work with both touch and click events (mouse + ...
0
votes
1answer
1k views

Handling multiple asynchronous events - Wait for pending offers to process on new offer?

I have a programming problem, that I don't know how to solve. And while I have provided a sample of my code, I am interested in a conceptual answer on how to resolve this problem. On a tradeOffers ...
1
vote
0answers
41 views

Push instead of pull on a list that might change due to a command in addition to events? [closed]

I need to show a refreshable/searchable list of items and update/add-to it whenever an event is published. How do I make sure no events are lost while refreshing/searching is happening? Some sort of ...
0
votes
2answers
1k views

Are hooks really subsumed by Slim Framework middleware?

I've been using the Slim Framework (v2) for a little while now to develop my user management system. They recently released Slim 3, and according to the upgrade guide, Slim v3 no longer has the ...
2
votes
0answers
46 views

How do you use Domain Events without obfuscating the control flow? [duplicate]

When we have a system which utilizes Domain Events, it can be quite hard to comprehend the whole workflow (sequence of events) of processing a particular command: how many active handlers we have, how ...