Akka/Scala example source code file (LeastShardAllocationStrategySpec.scala)

This example Akka source code file (LeastShardAllocationStrategySpec.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Akka and Scala source code examples by using tags.

All credit for the original source code belongs to akka.io; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Akka tags/keywords

actor, akka, akkaspec, leastshardallocationstrategy, leastshardallocationstrategyspec, map, pattern, set, test, testing, testkit, vector

The LeastShardAllocationStrategySpec.scala Akka example source code

/**
 * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
 */
package akka.contrib.pattern

import akka.testkit.AkkaSpec
import akka.actor.Props

class LeastShardAllocationStrategySpec extends AkkaSpec {
  import ShardCoordinator._

  val regionA = system.actorOf(Props.empty, "regionA")
  val regionB = system.actorOf(Props.empty, "regionB")
  val regionC = system.actorOf(Props.empty, "regionC")

  val allocationStrategy = new LeastShardAllocationStrategy(rebalanceThreshold = 3, maxSimultaneousRebalance = 2)

  "LeastShardAllocationStrategy" must {
    "allocate to region with least number of shards" in {
      val allocations = Map(regionA -> Vector("shard1"), regionB -> Vector("shard2"), regionC -> Vector.empty)
      allocationStrategy.allocateShard(regionA, "shard3", allocations) should be(regionC)
    }

    "rebalance from region with most number of shards" in {
      val allocations = Map(regionA -> Vector("shard1"), regionB -> Vector("shard2", "shard3"),
        regionC -> Vector.empty)

      // so far regionB has 2 shards and regionC has 0 shards, but the diff is less than rebalanceThreshold  
      allocationStrategy.rebalance(allocations, Set.empty) should be(Set.empty)

      val allocations2 = allocations.updated(regionB, Vector("shard2", "shard3", "shard4"))
      allocationStrategy.rebalance(allocations2, Set.empty) should be(Set("shard2"))
      allocationStrategy.rebalance(allocations2, Set("shard4")) should be(Set.empty)

      val allocations3 = allocations2.updated(regionA, Vector("shard1", "shard5", "shard6"))
      allocationStrategy.rebalance(allocations3, Set("shard1")) should be(Set("shard2"))
    }

    "must limit number of simultanious rebalance" in {
      val allocations = Map(regionA -> Vector("shard1"),
        regionB -> Vector("shard2", "shard3", "shard4", "shard5", "shard6"), regionC -> Vector.empty)

      allocationStrategy.rebalance(allocations, Set("shard2")) should be(Set("shard3"))
      allocationStrategy.rebalance(allocations, Set("shard2", "shard3")) should be(Set.empty)
    }
  }
}