Why event driven programming is important in web application

Callback functions have predetermined interfaces, which may differ slightly depending on the event type. The message loop invokes the callback function upon discovering the message at the head of the queue corresponding to that event type. For the function to be executed in the EDP process, the programming language in which this is done should provide a method of associating events with specific callback functions. Event-based apps differ from one another, depending on their purposes and functionality.

Nevertheless, they all have to possess a universal set of features, such as:. Python is also used as a suitable EDP tool. This approach to software coding possesses numerous advantages for all stakeholders. It requires fewer coded decisions than console applications.

Many events are determined by user actions instead of advance coding of all possible scenarios. While console-based apps act, event-driven apps react. Second, it removes the possibility of invalid value entry. A console-based app asks a question and allows the user to type the answer. Event-Based apps commonly offer a set of options either as buttons or as a drop-down menu. ODP is perfectly suited for the recent software engineering trends, such as cloud computing, microservices, and the need for enhanced scalability with flexible, distributed systems.

The use of ODP removes the need to correct and adjust the existing code when adding or removing some module.

The ODP system continues working flawlessly regardless of any adjustments of such kinds. Thus, programmers praise the ODP paradigm for being intuitive and well-suited to applications with control flows based on a complex of internal and external events rather than on structure.

But what is an event-driven application and how does it differ from a traditional request-driven application? An event-driven application is designed to detect events as they occur, and then deal with them using some event-handling procedure.

Event programming is not a type of technology or programming language, but an approach that is implemented during the product development stage. In an event-driven application, there is generally a main loop that listens for events, and then triggers a call-back function when one of those events is detected.

In this way, in an event-driven application, the flow of the program is determined by events such as user actions mouse clicks, key presses , sensor outputs, or messages from other programs or threads. 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. What is event-driven in NodeJS? Is NodeJS event driven? What the heck is event loop? Is NodeJS multithreaded?

Is NodeJS asynchronous? What is concurrency in NodeJS? Why is node js not multithreaded? Why is node js used? Is node JS asynchronous by default? Is Django multithreaded? Is Django asynchronous? Should I use node js or Django? Can I use node js with Django?

Is node js a backend? Do I need to know JavaScript for Django? Can Django replace JavaScript? Can Django replace PHP? Is Django easier than PHP? Is Django easy to learn? If one application is overloaded, then we can create new instances of that application to accommodate the increased number of requests.

But scaling up applications is not challenge-free, especially if we deal with stateful applications. Before microservices, this job was simple. All the data resided in a single place, typically some sort of relational database.

But when multiple services share a database, you may create problems like dependencies between teams on schema changes or performance issues.

A common pattern to solve this issue is to use a database per service. A distributed source of truth really helps maintain clean architecture, but we now have to deal with distributed transactions and the complexity of maintaining multiple databases. 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.

But then, service A needs to call service B, and the fun goes on. The problem with this behaviour is that if a service has resources blocked e.

If we allow a ms timeout per service and there are five service calls in the chain, then the first service would need to have a ms 2. Event-driven architecture EDA is a software architecture paradigm promoting the production, detection, consumption of, and reaction to events. In the classic three-tier applications, the core of our system was the data base. In EDA, the focus is shifted towards the events and how they are flowing through the system. This shift allowed us to completely change the way we design applications tackling the problems mentioned above.

An event is an action that triggers either a notification or some kind of change in the state of the application. A light has been switched on notification , the thermostat turned off the heating system notification , a user changed his address state change , or one of your friends changed his phone number state change.

In order for an event to be added, it must be relevant to the business. Which events are relevant to a business might be obvious when you think about them, but some of them might not.

Especially those events that occur as a reaction to other events. To discover events that are flowing through the system, use a technique called Event Storming. Bring together the stakeholders on an application from software engineers to business people and domain experts and map out all the business processes as specific events.

After all the business processes are mapped, the result can be used by engineering teams as requirements to build their applications. Events flow in a single direction, from a producer to a consumer.

Compare this with a REST call. The event producer never expects a response from the consumer, while in a REST call there will always be a response. No response, no need to block the code execution until something else happens.