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Examples of resilience4j-circuitbreaker

Create a CircuitBreakerRegistry

Create a CircuitBreakerRegistry with a custom CircuitBreakerConfig.

// Create a custom configuration for a CircuitBreaker
CircuitBreakerConfig circuitBreakerConfig = CircuitBreakerConfig.custom()
    .recordExceptions(IOException.class, TimeoutException.class)
    .ignoreExceptions(BusinessException.class, OtherBusinessException.class)

// Create a CircuitBreakerRegistry with a custom global configuration
CircuitBreakerRegistry circuitBreakerRegistry =

Create a CircuitBreaker

Get a CircuitBreaker from the CircuitBreakerRegistry with the global default configuration

CircuitBreaker circuitBreaker = circuitBreakerRegistry

Decorate a functional interface

Decorate your call to BackendService.doSomething() with a CircuitBreaker and execute the decorated supplier and recover from any exception.

Supplier<String> decoratedSupplier = CircuitBreaker
    .decorateSupplier(circuitBreaker, backendService::doSomething);

String result = Try.ofSupplier(decoratedSupplier)
    .recover(throwable -> "Hello from Recovery").get();

Execute a decorated functional interface

When you don't want to decorate your lambda expression, but just execute it and protect the call by a CircuitBreaker.

String result = circuitBreaker

Recover from an exception

If you want to recover from an exception after the CircuitBreaker recorded it as a failure, you can chain the method Try.recover(). The recovery method is only invoked, if Try.of() returns a Failure<Throwable> Monad.

// Given
CircuitBreaker circuitBreaker = CircuitBreaker.ofDefaults("testName");

// When I decorate my function and invoke the decorated function
CheckedFunction0<String> checkedSupplier =
  CircuitBreaker.decorateCheckedSupplier(circuitBreaker, () -> {
    throw new RuntimeException("BAM!");
Try<String> result = Try.of(checkedSupplier)
        .recover(throwable -> "Hello Recovery");

// Then the function should be a success, 
// because the exception could be recovered
// and the result must match the result of the recovery function.
assertThat(result.get()).isEqualTo("Hello Recovery");

If you want to recover from an exception before the CircuitBreaker records it as a failure, you can do the following:

Supplier<String> supplier = () -> {
            throw new RuntimeException("BAM!");

Supplier<String> supplierWithRecovery = SupplierUtils
  .recover(supplier, (exception) -> "Hello Recovery");

String result = circuitBreaker.executeSupplier(supplierWithRecovery);

assertThat(result).isEqualTo("Hello Recovery");

SupplierUtils and CallableUtils contain other methods like andThen which can take can be used to chain functions. For example to check the status code of a HTTP response, so that exceptions can be thrown.

Supplier<String> supplierWithResultAndExceptionHandler = SupplierUtils
  .andThen(supplier, (result, exception) -> "Hello Recovery");

Supplier<HttpResponse> supplier = () -> httpClient.doRemoteCall();
Supplier<HttpResponse> supplierWithResultHandling = SupplierUtils.andThen(supplier, result -> {
    if (result.getStatusCode() == 400) {
       throw new ClientException();
    } else if (result.getStatusCode() == 500) {
       throw new ServerException();
    return result;
HttpResponse httpResponse = circuitBreaker

Reset CircuitBreaker

The Circuit Breaker supports resetting to its original state, losing all the metrics and effectively resetting its Sliding Window.

CircuitBreaker circuitBreaker = CircuitBreaker.ofDefaults("testName");

Transition to states manually

CircuitBreaker circuitBreaker = CircuitBreaker.ofDefaults("testName");
// circuitBreaker.onFailure(...) won't trigger a state change
circuitBreaker.transitionToClosedState(); // will transition to CLOSED state and re-enable normal behaviour, keeping metrics
// circuitBreaker.onSuccess(...) won't trigger a state change
circuitBreaker.reset(); //  will transition to CLOSED state and re-enable normal behaviour, losing metrics

Override the RegistryStore

You can override the im-memory RegistryStore by a custom implementation. For example, if you want to use a Cache which removes unused instances after a certain period of time.

CircuitBreakerRegistry circuitBreakerRegistry = CircuitBreakerRegistry.custom()
  .withRegistryStore(new CacheCircuitBreakerRegistryStore())