petitviolet / supervisor   0.3.0

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CircuitBreaker implementation with Akka.Actor

Scala versions: 2.12

Supervisor

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A circuit-breaker implementation with Akka.Actor.

CircuitBreaker provides stability and resilience.

How to use

write dependency in your build.sbt.

libraryDependencies += "net.petitviolet" %% "supervisor" % "<latest version>"
// libraryDependencies += "net.petitviolet" % "supervisor_2.12" % "<latest version>"

Usage

I call circuit-breaker as Supervisor. You can use it just like an ActorRef.

simple example

import net.petitviolet.supervisor._

import scala.concurrent.duration._
// create Supervisor instance
val supervisorActor: ActorRef = system.actorOf(Supervisor.props(
  maxFailCount = 2,
  runTimeout = 1000.milliseconds,
  resetWait = 3000.milliseconds
))

// other ActorRef
val actorRef = system.actorOf(Props[SomeYourActor])

// supervising asynchronous procedure which is enveloped by `Execute`
supervisorActor ? Execute(actorRef ? Message("1")) onComplete { 
  case Success(x) =>
    println(s"result =>$x") 
  case Failure(t) =>
    t.printStackTrace()
}

Creation Supervisor

Supervisor needs 3 values.

  • maxFailCount
    • if failure count gets more than equal this limit, Supervisor state gets Open
  • runTimeout
    • wait time for asynchronous process by Supervisor
  • resetWait
    • when Supervisor state is Open and past this duration, its state gets Half-Open

specifying above values

import net.petitviolet.supervisor._

import scala.concurrent.duration._
// create Supervisor instance
val supervisorActor: ActorRef = system.actorOf(Supervisor.props(
  maxFailCount = 2,
  runTimeout = 1000.milliseconds,
  resetWait = 3000.milliseconds
))

specifying at configuration file

Using Typesafe Config library.

In some conf file, for example application.conf, write like below.

supervisor {
  max-fail-count = 2
  run-timeout = 1000
  reset-wait = 3000
}

The key supervisor is modifiable, but others are not.

val config = ConfigFactory.load().getConfig("supervisor")

val supervisorActor: ActorRef = system.actorOf(Supervisor.props(config))

use Supervisor as a CircuitBreaker

ActorRef instance of Supervisor supervises asynchronous procedures. When you wrap your scala.concurrent.Future instance in Execute and tell or ask to it, it works as a CircuitBreaker.

// other ActorRef for example to create Future.
val actorRef = system.actorOf(Props[SomeYourActor])

// supervising asynchronous procedure which is enveloped by `Execute`.
// Of cource you can use `tell` instead of `ask`, when you do not need result of Future.
supervisorActor ? Execute(actorRef ? Message("1")) onComplete { 
  case Success(x) =>
    println(s"result =>$x") 
  case Failure(t) =>
    t.printStackTrace()
}

Supervisor state

There are the same 3 states as CircuitBreaker. Simple description of each states is below.

  • Close
    • normal state.
    • Supervisor try to given process done normally with waiting runTimeout duration.
  • Open
    • Aborting Future.
    • When the state is Close and the count of Future gets Failure or exceeded runTimeout, it's state gets Open.
  • Half-Open
    • on the way of it's state to Close from Open.
      • It's state is Open and past resetWait duration, it gets Half-Open.
    • It make only 1 try, when Success, gets Close, otherwise when Failure, gets Open.

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