Explain the principle of operation and purpose of the Circuit Breaker component in reliability systems.

The Circuit Breaker component is used to increase the reliability of distributed systems by preventing repeated calls to a failing service and reducing system load.

Working principle:

1. Closed state: All requests pass as usual.
2. Open state: If the error count exceeds a threshold, the Circuit Breaker "opens" and blocks further requests, immediately returning an error or an alternative response.
3. Half-Open state: After some time, the Circuit Breaker allows a limited number of requests to check if the service has recovered.

If the requests are successful, it switches back to the closed state; otherwise, it opens again.

This prevents excessive load on the failed service and allows time for recovery, improving overall system stability.

Example in Go (simplified):

// Pseudocode
cb := NewCircuitBreaker(3, time.Minute) // 3 errors - opens for 1 minute

if cb.AllowRequest() {
    err := callRemoteService()
    if err != nil {
        cb.RecordFailure()
    } else {
        cb.RecordSuccess()
    }
} else {
    // Return error immediately, service is unavailable
}