In today's fast-paced software development landscape, microservices architecture has become a popular choice for building scalable and resilient applications. However, with the increase in distributed systems, the likelihood of failures also rises. One effective way to mitigate these failures is by implementing circuit-breaker patterns. This article delves into the Kong Back-end Service Circuit-Breaker, a vital component for enhancing the resilience of microservices.

Why Circuit Breakers Matter

Imagine a scenario where a service in your microservices architecture becomes unresponsive due to a high load or a temporary outage. Without a circuit breaker, other services that depend on it will continue to make requests, leading to a cascading failure throughout the system. This situation can cause significant downtime and degrade user experience. Implementing a circuit-breaker pattern helps to prevent such failures by stopping requests to a failing service and allowing it to recover.

Understanding the Circuit-Breaker Pattern

The circuit-breaker pattern is analogous to an electrical circuit breaker. When the circuit is functioning normally, electricity flows freely. However, when there is a fault, the circuit breaker trips, stopping the flow of electricity to prevent damage. Similarly, in a microservices context, the circuit breaker monitors the requests to a service and 'trips' when it detects failures, allowing the service to recover without overwhelming it with requests.

Core Principles

• Closed State: In this state, requests are allowed to pass through to the service. The circuit breaker monitors the success and failure rates of requests.
• Open State: If the failure rate exceeds a predefined threshold, the circuit breaker trips and enters the open state, blocking all requests to the service.
• Half-Open State: After a specified period, the circuit breaker allows a limited number of requests to pass through to test if the service has recovered. If successful, it returns to the closed state; otherwise, it remains open.

Kong Back-end Service Circuit-Breaker

Kong, a popular open-source API gateway, provides built-in support for the circuit-breaker pattern. By leveraging Kong's circuit-breaker plugin, developers can easily implement this pattern in their microservices architecture.

Installation and Configuration

curl -i -X POST http://localhost:8001/plugins/ 
  --data "name=circuit-breaker" 
  --data "config.timeout=5000" 
  --data "config.max_failures=5" 
  --data "config.reset_timeout=30000"

In the above command, we configure the circuit breaker with a timeout of 5000 ms, a maximum of 5 failures before tripping, and a reset timeout of 30000 ms.

Practical Application Demonstration

Let’s consider a practical example where we implement the circuit-breaker pattern using Kong. Suppose we have a microservice architecture with an authentication service and a user profile service. We want to protect the user profile service from being overwhelmed if the authentication service fails.

Step 1: Create Services

curl -i -X POST http://localhost:8001/services/ 
  --data "name=auth-service" 
  --data "url=http://auth-service:5000"
curl -i -X POST http://localhost:8001/services/ 
  --data "name=user-profile-service" 
  --data "url=http://user-profile-service:5000"

Step 2: Configure Circuit Breaker

curl -i -X POST http://localhost:8001/services/user-profile-service/plugins/ 
  --data "name=circuit-breaker" 
  --data "config.timeout=5000" 
  --data "config.max_failures=3" 
  --data "config.reset_timeout=10000"

Step 3: Testing the Circuit Breaker

To test the circuit breaker, simulate a failure in the authentication service and observe how the user profile service behaves. You can use tools like Postman or curl to send requests to the user profile service and see how the circuit breaker responds.

Experience Sharing and Skill Summary

In my experience implementing the Kong Back-end Service Circuit-Breaker, I learned that fine-tuning the configuration parameters is crucial. Setting appropriate thresholds for timeouts and failure rates can significantly impact the resilience of your microservices. Additionally, monitoring and logging are essential to understanding the behavior of your circuit breaker and making informed adjustments.

Conclusion

The Kong Back-end Service Circuit-Breaker is a powerful tool for enhancing the resilience of microservices. By preventing cascading failures and allowing services to recover gracefully, it ensures a smoother user experience. As the complexity of microservices architecture grows, adopting circuit-breaker patterns will be increasingly important. Future research could explore advanced strategies for combining circuit breakers with other resilience patterns like bulkheads and retries.

Editor of this article: Xiaoji, from AIGC