Retry.scala

package org.mccv
 
/**
 * A marker trait indicating an exception that is recoverable.
 * Note that we could make this a trait as well.
 */
class RecoverableException extends Exception
 
/**
 * Usage of our retryable class
 */
object Retryer {
	/**
	* The workhorse.  Runs the operation, and if successful returns the result.
	* If unsuccessful calls itself recursively with a decremented run number.
	*/
	def tryNTimes[T](func: () => T, runNumber: Int):T = {
	  println("running it with " + runNumber + " tries remaining")
	  try{
		  func()
	  } catch {
	    case e:RecoverableException if runNumber > 1 => tryNTimes(func,runNumber - 1)
	    case e => throw e
	  }
	}
}
 
object Main {
   def main(args: Array[String]):Unit = {
    val tries = 3;
    try{
    	println(Retryer.tryNTimes[String](flakyMethod,tries))
     }catch{
       case e => println("failed after " + tries + " tries")
     }
  }
 
  def flakyMethod():String = {
    if(Math.random > 0.3){
      throw new RecoverableException()
    }else{
      "foo"
    }
  }
}