2025-02-05
Event-Driven Architecture (EDA) is a design paradigm that promotes the production, detection, consumption, and reaction to events. In an EDA-based application, different components communicate by sending and receiving events. But what exactly is an event? It is an occurrence that has happened in the application. Some examples of events include:
- A customer signing up for your application
- A payment is received for an order
- A failed authentication attempt
There are mainly three different patterns for handling events in EDA:
1. Event Notifications
In this approach, events are used to notify that something has occurred within your application. Such an event carries the absolute minimum state, often just the identifier (ID) of an entity. When receiving such events, some components may record the information for auditing purposes, while others might call the source component to fetch additional information about the event. These events are general-purpose and suitable for broadcasting requirements, with less data sent over the network.
Example Command:
<h1>Simulating an event notification using curl</h1>
curl -X POST -H "Content-Type: application/json" -d '{"event_id": "12345", "event_type": "user_signup"}' http://example.com/event-notification
2. Event-Based State Transfer
This pattern is akin to the asynchronous relative of REST. Instead of REST’s on-demand pull model, event-based state transfer follows a push approach. Data (ID + information) is sent out to be consumed by any components. Some components may create their own local cached copies of the data, while others may take some other action based on the data received. The advantage of this approach is that the consumer need not call back the source component for additional information, as the entire information is right there in the event payload.
Example Command:
<h1>Simulating an event-based state transfer using curl</h1>
curl -X POST -H "Content-Type: application/json" -d '{"event_id": "67890", "event_type": "payment_received", "amount": 100}' http://example.com/event-state-transfer
3. Event Sourcing
This pattern is not about event transmission but event storage. Changes to an entity are not captured as irreversible modifications but are stored as events in an event store. These changes can be read and processed to recreate the final state of an entity whenever required.
Example Command:
<h1>Simulating event sourcing using a simple log file</h1>
echo '{"event_id": "54321", "event_type": "authentication_failed", "timestamp": "2023-10-01T12:00:00Z"}' >> /var/log/event_store.log
What Undercode Say
Event-Driven Architecture is a powerful paradigm that can significantly enhance the scalability and responsiveness of your applications. By understanding and implementing the three main patterns—Event Notifications, Event-Based State Transfer, and Event Sourcing—you can design systems that are more resilient, flexible, and capable of handling complex workflows.
Linux Commands for EDA:
1. Kafka for Event Streaming:
<h1>Start a Kafka server</h1> bin/kafka-server-start.sh config/server.properties
<h1>Create a Kafka topic</h1> bin/kafka-topics.sh --create --topic user_signup --bootstrap-server localhost:9092
<h1>Produce a message to the Kafka topic</h1> bin/kafka-console-producer.sh --topic user_signup --bootstrap-server localhost:9092
2. Redis for Event Caching:
<h1>Set a key in Redis</h1>
redis-cli set event:12345 '{"event_id": "12345", "event_type": "user_signup"}'
<h1>Get a key from Redis</h1> redis-cli get event:12345
3. Logstash for Event Logging:
<h1>Start Logstash with a configuration file</h1> bin/logstash -f logstash.conf
<h1>Example Logstash configuration</h1>
input {
file {
path => "/var/log/event_store.log"
start_position => "beginning"
}
}
output {
elasticsearch {
hosts => ["localhost:9200"]
}
}
4. Curl for Event Simulation:
<h1>Simulate an event notification</h1>
curl -X POST -H "Content-Type: application/json" -d '{"event_id": "12345", "event_type": "user_signup"}' http://example.com/event-notification
5. Cron Jobs for Scheduled Events:
<h1>Schedule a cron job to run a script every hour</h1> 0 * * * * /path/to/your/script.sh
Useful URLs:
By leveraging these commands and tools, you can effectively implement and manage Event-Driven Architecture in your systems. Whether you’re handling user signups, processing payments, or managing authentication events, EDA provides a robust framework for building scalable and responsive applications.
References:
Hackers Feeds, Undercode AI
