Can you explain how the Circuit Breaker works and why it is needed in high-load systems?

Circuit Breaker is a pattern that helps protect a system from cascading failures when working with external services or components.

How it works:

• In normal state, the Circuit Breaker allows requests to the external service.
• If the error count exceeds a set threshold, the Circuit Breaker "opens" and blocks further requests for a period.
• After a pause, it attempts to restore the connection (half-open state).
• If requests succeed, the Circuit Breaker returns to normal.

Why it's needed:

• Prevents excessive load on a failed service.
• Reduces response wait time by quickly returning errors.
• Increases system resilience and fault tolerance.

Example in Go using the github.com/sony/gobreaker library:

import (
    "fmt"
    "github.com/sony/gobreaker"
)

func main() {
    cb := gobreaker.NewCircuitBreaker(gobreaker.Settings{})

    result, err := cb.Execute(func() (interface{}, error) {
        // call to external service
        return "response", nil
    })

    if err != nil {
        fmt.Println("Error or Circuit Breaker is open:", err)
    } else {
        fmt.Println("Successful response:", result)
    }
}