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Questions tagged [event]

The tag has no usage guidance.

2
votes
2answers
72 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 ...
0
votes
1answer
35 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, by ...
5
votes
2answers
171 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 (...
3
votes
3answers
95 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
48 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 ...
0
votes
2answers
352 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
0answers
53 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
249 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
173 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
267 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
215 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
684 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
155 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
0answers
246 views

MVVM Portable ViewModel / WPF/Xamarin Messaging

I have a WPF app targeting .NET 4 which I am updating and maintaining for a customer. In the course of the project, we have also ported the functionality to a Xamarin mobile app. I was able to ...
0
votes
1answer
109 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
421 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
279 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
135 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 ...
5
votes
3answers
3k 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
585 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 ...
3
votes
1answer
204 views

Domain Events Groupping/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 ...
6
votes
4answers
5k 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
255 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 ...
13
votes
3answers
3k 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
59 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 ...
5
votes
1answer
74 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 ...
4
votes
2answers
1k 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
927 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
39 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
932 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
43 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 ...
0
votes
2answers
374 views

Design pattern for canceling a long task in a sub-thread

Suppose we have a file copy program. It has two threads, a UI thread displaying the progress of the copy operation and a work thread copying the file. The UI has a button for canceling the process. ...
0
votes
4answers
287 views

How should nodes in a chain be connected?

Suppose you were building a system that receives data on one end and sends filtered data on the other end. The system is a chain of nodes, each receiving data from the node before and sending ...
2
votes
2answers
361 views

Performance increase by only attach onblur handler inside of onfocus handler?

Given a web page with input fields, does it have a performance difference whether or not you assign the onblur handler inside of the onfocus handler like so: var inputFields = document....
5
votes
2answers
2k views

Should I use events or abstract methods?

Lets say I create an abstract class that manages some network functionality for me. I want to be able to be notified when something changes. For example: OnConnect or OnDisconnect. Should I create ...
1
vote
2answers
5k views

How to write a custom EventHandler class

When I started using Java, I created a custom Event class to mimic C#'s implementation of Events. Since then, I've added some other features, like event listener priorities, and cascading events were ...
1
vote
3answers
20k views

Detect or Prevent Screen Capture Applications

I am building an app that displays very sensitive information and as such, I want to be able to either Disable the ability to capture the screen Redact the portion of my app that is on the screen ...
8
votes
2answers
3k views

Should the sender of an event always be a generic Object?

When programming events in C#, it is advised to create a delegate in form of: delegate XEventHandler(object sender, XEventArgs e); My question is on the first argument of the delegate, object sender....
1
vote
1answer
1k views

How is Nginx handling its requests in terms of tasks or threading?

Recently I read up on Wikipedia about Nginx. What puzzled me was this paragraph: Nginx uses an asynchronous event-driven approach to handling requests, instead of the Apache HTTP Server model that ...
0
votes
1answer
504 views

How does a clicked event work at a low level?

Specifically in regard to a drag and drop operation, how does a button, text box or whatever know that it has been clicked (or vice versa how does the display manager know what it clicked). I read ...
2
votes
1answer
808 views

will having an event with subscribers prevent an object from being GC'ed?

I have an object, which has an event which in turn has subscribers. I know that the subscribing objects won't get GC'ed since the delegate they stored for the event is connected to them, thus keeping ...
3
votes
2answers
2k views

Combining asynchronous and synchronous programming

I've got trouble wrapping my head around a certain problem: In my data-flow app (a visual editor), I have both autonomous objects which communicate though ports via unordered simultaneous messages ...
8
votes
2answers
1k views

Should event listeners be held in weak references?

Usually event listeners shouldn't outlive object that registered them. Does it mean that event listeners should be held by weak references by default (stored in weak collections by the object ...
5
votes
2answers
7k views

Testing C# Eventhandler Subscription

I want my unit tests to be able to verify that some events were subscribed or unsubscribed at specific points. Currently, I see two options. VerifiableEventHandler Each client subscribes using the ...
8
votes
2answers
4k views

How to determine if a message should be a command message or event message?

Two enterprise integration patterns are the command message and the event message. I am working on a system in which we use messaging not only for integration with other systems, but for internal ...
0
votes
0answers
61 views

Event and Objects

I have an array of objects. Instead of me when performing a task asking every object If they have anything to say about that, I would rather like the following: Perform Task Object #4 Hey, I have ...
0
votes
1answer
2k views

Good practice using signals and event driven system

I am using signals (specifically Boost signals2) to create an event driven protocol API and model. Most elements have their own signals, and there are usually multiple of each element. Consider a ...
7
votes
3answers
3k views

Event-driven vs. 'reference'-driven programming (i.e. in JavaScript)

I haven't been able to find the appropriate terminology to search for content on the web related to what I'm asking, so I'm hoping someone on here can at least point me in the right direction. I'm a ...
3
votes
1answer
2k views

Root cause analysis in event correlation

I'm to write an event correlator module for the device we produce. When a fault occurs the resulting avalanche of logs about derivative conditions from various modules is readable only to a person ...
-1
votes
2answers
472 views

Access functions from user control without events?

On some generic functions, it seems that accessing a function on mainform directly from the usercontrol is easier than raising an event. For example: A function on main form that displays one desired ...