Since it offers the most value for GUI applications, some other use cases might not benefit from it. Some critics are also saying that event-driven programming is complex to master and not worth the trouble when your application is very simple and small. See the original article here. Thanks for visiting DZone today,. Edit Profile. Sign Out View Profile.
Event-driven programming is applied extensively in graphical user interfaces and applications that perform certain actions in response to user input for example, JavaScript web applications. For software teams, developing an event-driven application inevitably adds complexity to system design and delivery. This is because traditional software architectures are based on request-driven interactions rather than event-driven interactions.
In the request-driven case, the customer drives the interactions, dictating which service will process the request. The customer must then wait for a response to the request. The system constituents that do this can be either simple services or very complex systems. Their role is to produce or consume events and trigger actions. Nevertheless, event-driven applications can still require some traditional request-driven design to be built in, as they can complement and enhance one another, depending on the type of business process being implemented.
During my university undergraduate degree, the concepts of event-driven systems and real-time applications were covered as different subjects. The missing element in my event-driven development journey was the bridge between those theoretical concepts and their actual implementation. I will briefly highlight four areas that covered messaging and event-driven systems — Frontend and Game Development, Programming Design Patterns, Networking Fundamentals, and Operating Systems Fundamentals — followed by a table that maps the theoretical concepts to event-driven architecture lingo.
Interacting with UI elements in front end development is event-driven in nature. For example, a button does not poll its state to check if it is pressed or not, it simply registers an EventListener with a callback function that gets triggered upon an event being fired.
A simple implementation takes the following format:. Since JavaScript is single-threaded and can only do one thing at a time, the browser has an event loop that keeps track of all the events in an event queue which can be accessed through interfaces built on top of the core JavaScript language. Whenever an event occurs in the web browser, the event loop dispatches this event to any registered listener.
Sweet and simple. Note that the event loop implements the reactor pattern design discussed in the following section. In game development, the concepts of EventHandlers and EventDispatchers are very prevalent for asynchronous interactions with a game.
Software design patterns present reusable solutions to common problems. For real-time applications, I will give a high-level overview of two common design patterns that present an event-driven approach versus a thread-based approach:. This pattern relies on the concepts of dispatching events.
The benefit of the reactor pattern is to avoid having dedicated threads for each message, connection, or request. As seen in the diagram above, events are demultiplexed and dispatched to the responsible handler. The observer pattern differs from the reactor pattern in a way that each object maintains a list of its dependents. A change in state for an object will simply trigger a notification i. Recalling the OSI model covered earlier, the network layer was a HUGE help to me when it came to understanding event-driven architecture and development.
This layer is responsible for receiving packets of data in the internet stack and delivering them to the intended destination through IP routing.
Every packet traveling through the internet has a logical address to its destination IP that is handled by the router middleware hardware that literally routes the packet to other destinations in the network. These packets could either be destined to hosts within the network boundary egress traffic or traffic coming in from outside the network boundary Ingress traffic. Similar to the reactor pattern discussed earlier, scheduling and threading in an operating system embodies the concepts of dispatching and demultiplexing.
There are six popular scheduling algorithms , but in a very simplistic overview, scheduling enables asynchronous activities in operating systems and minimizes any resource starvation. Matching the foundational theoretical concepts discussed in the section above to the event-driven architecture equivalent aided me in my event-driven development journey.
I summarized them in this table:. If REST APIs have already been adopted for building applications and is considered the de facto solution in many industries, why should we bother ourselves with finding an alternative? Why should we consider an event-driven approach for operational use cases? Great post Bogdan! Wish there is some series of posts , podcasts exclusively for this topic which interlink to other major topics like distributed transactions, eventual consistency and so on… Appreciate if anyone can add few links references as I have always been on hunt of related topics, design patterns.
Thank you! Anil, I and other academics have been exploring problems related to the event-driven architecture. See the references of the articles for other related work. I also saw [4] go by which improves on my work in [1]. Interesting topic, i work in am event driven architecture. The Idee is to use a sharepoint as a document Store Important for the collaboration of our users.
But not all users of the platform are sharepoint users. Also i have different Sites in sharepoint where the documents are located. But it will break the event driven architecture. It looks that your scenario maybe is one of those problems, and that is ok!
You will never find a purely event-driven company. Most of the time, you will see a mix between eventing and synchronous APIs. There are 3 types of communication between services: events, queries, and commands.
Events represent an action that happened in the past, and there is no response attached to it. A query represents an action happening now, and there is always a response. Finally, a command represents an action that will happen sometime in the near future, and there is a possible response attached to it.
Looking at your scenario accessing a file while presenting a token , I can determine at least 2 actions: a query retrieve the file and a command generate one-time token. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment.
This site uses Akismet to reduce spam. Learn how your comment data is processed. Latest Newsletter Podcast Company. Scalability Scalability has much in common with availability. Single source of truth Before microservices, this job was simple. Synchronous In a typical request-response scenario, the client waits for the server to respond; it blocks all its activities until it receives a response or the timeout expires.
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