Failurewall

This is a library to protect applications against failures, and helpful in developing stable, responsive and resilient systems.

Failurewall is inspired by Hystrix and adapted for scala.concurrent.Future.

Getting Started

You should add the following dependency.

libraryDependencies += "com.okumin" %% "failurewall-core" % "0.2.0"

If you are using Akka 2.4, you can use failurewall-akka. failurewall-akka provides the following failurewalls.

• circuit breaker
• retry with backoff
• timeout

libraryDependencies += "com.okumin" %% "failurewall-akka" % "0.2.0"

If you are using Akka 2.3, see also failurewall-akka23.

How to use

As a Proxy

Failurewall is simple to use, wrapping scala.concurrent.Future to be protected. Each failurewall has abilities to handle failures.

object HttpClient {
  def get(url: String): Future[Response] = ???
}

val wall: Failurewall[Response, Response] = ???
val response: Future[Response] = wall.call(HttpClient.get("http://okumin.com/"))

Composability

Failurewalls has their own ability, e.g. retrying, checking rate limits and throttling. Failurewall#compose makes Failurewalls decorate such features.

val wallSina: Failurewall[Int, String] = ???
val wallRose: Failurewall[Int, Int] = ???
val wallMaria: Failurewall[Double, Int] = ???

val walls: [Double, String] = wallSina compose wallRose compose wallMaria

Built-in walls(failurewall-core)

RetryFailurewall

Retries on temporary failures.

val wall = RetryFailurewall[Response](10, executionContext)
wall.call(Future.failed(new RuntimeException)) // retry 10 times

StdSemaphoreFailurewall

Keeps resource usage constant.

val wall = StdSemaphoreFailurewall[Response](10, executionContext)
val results = (1 to 100).map { _ =>
  // fails immediately while other 10 calls are running
  wall.call(doSomeOperation())
}

StopwatchFailurewall

Measures the execution time.

val wall = StopwatchFailurewall[Response](executionContext)
wall.call(doSomeOperation()) // returns Future[(Try[Response], FiniteDuration)]

Built-in walls(failurewall-akka)

AkkaCircuitBreakerFailurewall

Prevents a failure from leading to cascading other failures.

// has a little complicated constructor
val wall: AkkaCircuitBreakerFailurewall[Response] = ???
val results = (1 to 100).map { _ =>
  // fail-fast after failure times exceeds the threshold
  wall.call(Future {
    throw new RuntimeException
  })
}

AkkaRetryFailurewall

Retries with backoff on temporary failures.

val backoffStrategy = ExponentialBackoffStrategy(
  minBackoff = 100.millis,
  maxBackoff = 10.seconds,
  multiplier = 2.0
)
val wall = AkkaRetryFailurewall[Response](
  10,
  backoffStrategy,
  akkaScheduler,
  executionContext
)
// retry 10 times with exponential backoff
wall.call(Future.failed(new RuntimeException))

AkkaTimeoutFailurewall

Times out when it takes some duration.

val wall = AkkaTimeoutFailurewall[String](5.seconds, akkaScheduler, executionContext) {
  logger.error("Timed out.")
}
// fails with FailurewallException
wall.call(Future {
  Thread.sleep(10000)
  "mofu"
})