Circuit Breaker Configuration Tool

Configuration

Failure Threshold (%) % failures to open circuit

Evaluation Window (requests) Min calls before decision

Sliding Window Type

Open Duration (seconds) Wait before half-open

Half-Open Requests Permitted during half-open

Slow Call Threshold (ms) Latency to count as slow

Slow Call Rate (%) Slow calls to trigger open

Presets

Simulate Requests

Circuit Breaker State

CLOSED

Accepting requests

Failure Rate

Total Calls

Blocked Calls

MTBF

-s

Failure Rate Threshold: 50%

Call History (last 50)

Event Log

Availability Metrics

Availability

100%

0 downtime periods

Implementation Code

Resilience4j (Java)

CircuitBreakerConfig config = CircuitBreakerConfig.custom()
    .failureRateThreshold(50)
    .slowCallRateThreshold(50)
    .slowCallDurationThreshold(Duration.ofMillis(1000))
    .waitDurationInOpenState(Duration.ofSeconds(30))
    .minimumNumberOfCalls(10)
    .permittedNumberOfCallsInHalfOpenState(3)
    .build();

CircuitBreaker breaker = CircuitBreaker.of("myBreaker", config);
breaker.executeSupplier(() -> callDownstream());

Polly (.NET)

var policy = Policy.Handle()
    .OrResult(r => !r.IsSuccessStatusCode)
    .CircuitBreaker(5, TimeSpan.FromSeconds(30),
        onBreak: (outcome, ts) => Console.WriteLine("Circuit opened"),
        onReset: () => Console.WriteLine("Circuit closed"));

var response = await policy.ExecuteAsync(() =>
    httpClient.GetAsync("https://api.example.com"));

opossum (Node.js)

const breaker = new CircuitBreaker(callFunction, {
    timeout: 1000,
    errorThresholdPercentage: 50,
    resetTimeout: 30000,
    rollingCountTimeout: 10000,
    rollingCountBuckets: 10,
    name: 'myService'
});

await breaker.fire(args).catch(err => {
    if (err.breaker) console.log('Circuit open');
});

Hystrix Pattern (Overview)

public class MyService {
    @HystrixCommand(
        fallbackMethod = "fallback",
        commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",
                            value = "1000"),
            @HystrixProperty(name = "circuitBreaker.errorThresholdPercentage",
                            value = "50"),
            @HystrixProperty(name = "circuitBreaker.sleepWindowInMilliseconds",
                            value = "30000")
        }
    )
    public String callDownstream() {
        return restTemplate.getForObject("...", String.class);
    }

    public String fallback() {
        return "Service unavailable";
    }
}