Hystrix Command Sample

GetDependencyCommand.scala

package commands

import com.netflix.hystrix.HystrixCommand
import com.netflix.hystrix.HystrixCommand.Setter
import com.netflix.hystrix.{ HystrixCommandGroupKey, HystrixCommandKey, HystrixCommandProperties }
import com.netflix.hystrix.HystrixCommandProperties.ExecutionIsolationStrategy

object GetDependencyCommand {
  final def settings: Setter = Setter
    .withGroupKey(HystrixCommandGroupKey.Factory.asKey("get-dependency-group"))
    .andCommandKey(HystrixCommandKey.Factory.asKey("GetDependencyCommand"))
    .andCommandPropertiesDefaults(
      HystrixCommandProperties.Setter()
        .withExecutionIsolationStrategy(ExecutionIsolationStrategy.THREAD) //Strategy could be Thread Pool or Semaphore
        .withCircuitBreakerSleepWindowInMilliseconds(1000) //Time before checking if circuit is healthy again
        .withCircuitBreakerErrorThresholdPercentage(70) //The threshold percentege in last 10s(default) to open circuit
        .withExecutionTimeoutInMilliseconds(2000) //Time waiting the response
    )
  
  def apply(dependencyCode: String): GetDependencyCommand = {
    new GetDependencyCommand(dependencyCode)
  }
}

class GetDependencyCommand(
  dependencyCode: String
) extends HystrixCommand[Unit](GetDependencyCommand.settings) {

  //EXECUTION: here is executed the function which makes a external call
  override def run(): Unit = {
    // Do a call
  }
  
  //FALLBACK: here is handled the fallback actions
  override def getFallback: Unit = {
    getFailedExecutionException match {
      case ex: DependencyFailureException => //failure fallback return throwed by your call in run
      case ex: HystrixRuntimeException => //decide what do when, eg.: circuit is open, timeout happens, thread rejects
    }
  }
}