Circuit Breaker Pattern
1. Introduction
The Circuit Breaker Pattern is a design pattern used in software development to prevent an application from repeatedly trying to execute an operation that is likely to fail. This pattern helps to improve the stability and resilience of the system by allowing it to gracefully handle failures.
2. Key Concepts
- State Management: The pattern has three states: Closed, Open, and Half-Open.
- Timeout: A duration after which the circuit breaker will allow a limited number of requests to pass through.
- Fallback: Defines what to do when the circuit is open, such as returning a default response.
3. Implementation
3.1 Basic Structure
class CircuitBreaker {
private State state;
private int failureThreshold;
private long timeout;
private long lastFailureTime;
public CircuitBreaker(int failureThreshold, long timeout) {
this.state = State.CLOSED;
this.failureThreshold = failureThreshold;
this.timeout = timeout;
}
public boolean call(Callable serviceCall) {
switch (state) {
case OPEN:
if (System.currentTimeMillis() - lastFailureTime > timeout) {
state = State.HALF_OPEN;
} else {
return false; // Circuit is open
}
break;
case HALF_OPEN:
// Allow limited calls and check for success
break;
case CLOSED:
// Proceed with the service call
break;
}
return true;
}
}
4. Best Practices
- Implement a fallback mechanism to handle failure gracefully.
- Monitor and log circuit state transitions and failures.
- Adjust the failure threshold based on system performance and requirements.
- Test the circuit breaker under various scenarios to ensure reliability.