onCompleteWithBreaker

Description

Evaluates its parameter of type CompletionStage<T> protecting it with the specified CircuitBreaker. Refer to Circuit Breaker for a detailed description of this pattern.

If the CircuitBreaker is open, the request is rejected with a CircuitBreakerOpenRejection. Note that in this case the request’s entity databytes stream is cancelled, and the connection is closed as a consequence.

Otherwise, the same behaviour provided by onComplete is to be expected.

Example

// import static scala.compat.java8.JFunction.func;
// import static akka.http.javadsl.server.PathMatchers.*;

final int maxFailures = 1;
final FiniteDuration callTimeout = FiniteDuration.create(5, TimeUnit.SECONDS);
final FiniteDuration resetTimeout = FiniteDuration.create(1, TimeUnit.SECONDS);
final CircuitBreaker breaker = CircuitBreaker.create(system().scheduler(), maxFailures, callTimeout, resetTimeout);

final Route route = path(segment("divide").slash(integerSegment()).slash(integerSegment()),
  (a, b) -> onCompleteWithBreaker(breaker,
    () ->  CompletableFuture.supplyAsync(() -> a / b),
    maybeResult -> maybeResult
      .map(func(result -> complete("The result was " + result)))
      .recover(new PFBuilder<Throwable, Route>()
        .matchAny(ex -> complete(StatusCodes.InternalServerError(),
          "An error occurred: " + ex.getMessage())
        )
        .build())
      .get()
  )
);

testRoute(route).run(HttpRequest.GET("/divide/10/2"))
  .assertEntity("The result was 5");

testRoute(route).run(HttpRequest.GET("/divide/10/0"))
  .assertStatusCode(StatusCodes.InternalServerError())
  .assertEntity("An error occurred: / by zero");
// opened the circuit-breaker 

testRoute(route).run(HttpRequest.GET("/divide/10/0"))
      .assertStatusCode(StatusCodes.ServiceUnavailable())
      .assertEntity("The server is currently unavailable (because it is overloaded or down for maintenance).");

Thread.sleep(resetTimeout.toMillis() + 300);
// circuit breaker resets after this time

testRoute(route).run(HttpRequest.GET("/divide/8/2"))
  .assertEntity("The result was 4");