Examples
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()
.failureRateThreshold(50)
.waitDurationInOpenState(Duration.ofMillis(1000))
.permittedNumberOfCallsInHalfOpenState(2)
.slidingWindowSize(2)
.recordExceptions(IOException.class, TimeoutException.class)
.ignoreExceptions(BusinessException.class, OtherBusinessException.class)
.build();
// Create a CircuitBreakerRegistry with a custom global configuration
CircuitBreakerRegistry circuitBreakerRegistry =
CircuitBreakerRegistry.of(circuitBreakerConfig);
Create a CircuitBreaker
Get a CircuitBreaker from the CircuitBreakerRegistry with the global default configuration
CircuitBreaker circuitBreaker = circuitBreakerRegistry
.circuitBreaker("name");
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
.executeSupplier(backendService::doSomething);
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
assertThat(result.isSuccess()).isTrue();
// 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
.executeSupplier(supplierWithResultHandling);
Reset CircuitBreaker
The Circuit Breaker supports resetting to its original state, losing all the metrics and effectively resetting its Ring Bit Buffer.
CircuitBreaker circuitBreaker = CircuitBreaker.ofDefaults("testName");
circuitBreaker.reset();
Transition to states manually
CircuitBreaker circuitBreaker = CircuitBreaker.ofDefaults("testName");
circuitBreaker.transitionToDisabledState();
// circuitBreaker.onFailure(...) won't trigger a state change
circuitBreaker.transitionToClosedState(); // will transition to CLOSED state and re-enable normal behaviour, keeping metrics
circuitBreaker.transitionToForcedOpenState();
// circuitBreaker.onSuccess(...) won't trigger a state change
circuitBreaker.reset(); // will transition to CLOSED state and re-enable normal behaviour, losing metrics
Updated about 5 years ago