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=cdd #17779 Create activator template for Distributed Data

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* includes the samples, with tutorial text description
This commit is contained in:
Patrik Nordwall 2015-06-29 21:18:39 +02:00
parent 33bc502c76
commit 252e88c082
29 changed files with 1278 additions and 821 deletions
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2
.gitignore vendored
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@ -23,6 +23,8 @@
.manager .manager
.multi-jvm .multi-jvm
.project .project
.sbtserver
.sbtserver.lock
.scala_dependencies .scala_dependencies
.scalastyle .scalastyle
.settings .settings

267
akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedServiceRegistrySpec.scala
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@ -1,267 +0,0 @@
/**
* Copyright (C) 2009-2015 Typesafe Inc. <http://www.typesafe.com>
*/
package sample.datareplication
import scala.concurrent.duration._
import akka.actor.Actor
import akka.actor.ActorLogging
import akka.actor.ActorRef
import akka.actor.PoisonPill
import akka.actor.Props
import akka.actor.Terminated
import akka.cluster.Cluster
import akka.cluster.ClusterEvent
import akka.cluster.ClusterEvent.LeaderChanged
import akka.cluster.ddata.DistributedData
import akka.cluster.ddata.GSet
import akka.cluster.ddata.ORSet
import akka.cluster.ddata.Replicator.GetReplicaCount
import akka.cluster.ddata.Replicator.ReplicaCount
import akka.cluster.ddata.STMultiNodeSpec
import akka.remote.testconductor.RoleName
import akka.remote.testkit.MultiNodeConfig
import akka.remote.testkit.MultiNodeSpec
import akka.testkit._
import com.typesafe.config.ConfigFactory
import akka.cluster.ddata.GSetKey
import akka.cluster.ddata.ORSetKey
import akka.cluster.ddata.Key
object ReplicatedServiceRegistrySpec extends MultiNodeConfig {
val node1 = role("node-1")
val node2 = role("node-2")
val node3 = role("node-3")
commonConfig(ConfigFactory.parseString("""
akka.loglevel = INFO
akka.actor.provider = "akka.cluster.ClusterActorRefProvider"
akka.log-dead-letters-during-shutdown = off
"""))
class Service extends Actor {
def receive = {
case s: String ⇒ sender() ! self.path.name + ": " + s
}
}
}
object ReplicatedServiceRegistry {
import akka.cluster.ddata.Replicator._
val props: Props = Props[ReplicatedServiceRegistry]
/**
* Register a `service` with a `name`. Several services
* can be registered with the same `name`.
* It will be removed when it is terminated.
*/
final case class Register(name: String, service: ActorRef)
/**
* Lookup services registered for a `name`. [[Bindings]] will
* be sent to `sender()`.
*/
final case class Lookup(name: String)
/**
* Reply for [[Lookup]]
*/
final case class Bindings(name: String, services: Set[ActorRef])
/**
* Published to `System.eventStream` when services are changed.
*/
final case class BindingChanged(name: String, services: Set[ActorRef])
final case class ServiceKey(serviceName: String) extends Key[ORSet[ActorRef]](serviceName)
private val AllServicesKey = GSetKey[ServiceKey]("service-keys")
}
class ReplicatedServiceRegistry() extends Actor with ActorLogging {
import akka.cluster.ddata.Replicator._
import ReplicatedServiceRegistry._
val replicator = DistributedData(context.system).replicator
implicit val cluster = Cluster(context.system)
var keys = Set.empty[ServiceKey]
var services = Map.empty[String, Set[ActorRef]]
var leader = false
def serviceKey(serviceName: String): ServiceKey =
ServiceKey("service:" + serviceName)
override def preStart(): Unit = {
replicator ! Subscribe(AllServicesKey, self)
cluster.subscribe(self, ClusterEvent.InitialStateAsEvents, classOf[ClusterEvent.LeaderChanged])
}
override def postStop(): Unit = {
cluster.unsubscribe(self)
}
def receive = {
case Register(name, service) ⇒
val dKey = serviceKey(name)
// store the service names in a separate GSet to be able to
// get notifications of new names
if (!keys(dKey))
replicator ! Update(AllServicesKey, GSet(), WriteLocal)(_ + dKey)
// add the service
replicator ! Update(dKey, ORSet(), WriteLocal)(_ + service)
case Lookup(key) ⇒
sender() ! Bindings(key, services.getOrElse(key, Set.empty))
case c @ Changed(AllServicesKey) ⇒
val newKeys = c.get(AllServicesKey).elements
log.debug("Services changed, added: {}, all: {}", (newKeys -- keys), newKeys)
(newKeys -- keys).foreach { dKey ⇒
// subscribe to get notifications of when services with this name are added or removed
replicator ! Subscribe(dKey, self)
}
keys = newKeys
case c @ Changed(ServiceKey(serviceName)) ⇒
val name = serviceName.split(":").tail.mkString
val newServices = c.get(serviceKey(name)).elements
log.debug("Services changed for name [{}]: {}", name, newServices)
services = services.updated(name, newServices)
context.system.eventStream.publish(BindingChanged(name, newServices))
if (leader)
newServices.foreach(context.watch) // watch is idempotent
case LeaderChanged(node) ⇒
// Let one node (the leader) be responsible for removal of terminated services
// to avoid redundant work and too many death watch notifications.
// It is not critical to only do it from one node.
val wasLeader = leader
leader = node.exists(_ == cluster.selfAddress)
// when used with many (> 500) services you must increase the system message buffer
// `akka.remote.system-message-buffer-size`
if (!wasLeader && leader)
for (refs ← services.valuesIterator; ref ← refs)
context.watch(ref)
else if (wasLeader && !leader)
for (refs ← services.valuesIterator; ref ← refs)
context.unwatch(ref)
case Terminated(ref) ⇒
val names = services.collect { case (name, refs) if refs.contains(ref) ⇒ name }
names.foreach { name ⇒
log.debug("Service with name [{}] terminated: {}", name, ref)
replicator ! Update(serviceKey(name), ORSet(), WriteLocal)(_ - ref)
}
case _: UpdateResponse[_] ⇒ // ok
}
}
class ReplicatedServiceRegistrySpecMultiJvmNode1 extends ReplicatedServiceRegistrySpec
class ReplicatedServiceRegistrySpecMultiJvmNode2 extends ReplicatedServiceRegistrySpec
class ReplicatedServiceRegistrySpecMultiJvmNode3 extends ReplicatedServiceRegistrySpec
class ReplicatedServiceRegistrySpec extends MultiNodeSpec(ReplicatedServiceRegistrySpec) with STMultiNodeSpec with ImplicitSender {
import ReplicatedServiceRegistrySpec._
import ReplicatedServiceRegistry._
override def initialParticipants = roles.size
val cluster = Cluster(system)
val registry = system.actorOf(ReplicatedServiceRegistry.props)
def join(from: RoleName, to: RoleName): Unit = {
runOn(from) {
cluster join node(to).address
}
enterBarrier(from.name + "-joined")
}
"Demo of a replicated service registry" must {
"join cluster" in within(10.seconds) {
join(node1, node1)
join(node2, node1)
join(node3, node1)
awaitAssert {
DistributedData(system).replicator ! GetReplicaCount
expectMsg(ReplicaCount(roles.size))
}
enterBarrier("after-1")
}
"replicate service entry" in within(10.seconds) {
runOn(node1) {
val a1 = system.actorOf(Props[Service], name = "a1")
registry ! Register("a", a1)
}
awaitAssert {
val probe = TestProbe()
registry.tell(Lookup("a"), probe.ref)
probe.expectMsgType[Bindings].services.map(_.path.name) should be(Set("a1"))
}
enterBarrier("after-2")
}
"replicate updated service entry, and publish to even bus" in {
val probe = TestProbe()
system.eventStream.subscribe(probe.ref, classOf[BindingChanged])
runOn(node2) {
val a2 = system.actorOf(Props[Service], name = "a2")
registry ! Register("a", a2)
}
probe.within(10.seconds) {
probe.expectMsgType[BindingChanged].services.map(_.path.name) should be(Set("a1", "a2"))
registry.tell(Lookup("a"), probe.ref)
probe.expectMsgType[Bindings].services.map(_.path.name) should be(Set("a1", "a2"))
}
enterBarrier("after-4")
}
"remove terminated service" in {
val probe = TestProbe()
system.eventStream.subscribe(probe.ref, classOf[BindingChanged])
runOn(node2) {
registry.tell(Lookup("a"), probe.ref)
val a2 = probe.expectMsgType[Bindings].services.find(_.path.name == "a2").get
a2 ! PoisonPill
}
probe.within(10.seconds) {
probe.expectMsgType[BindingChanged].services.map(_.path.name) should be(Set("a1"))
registry.tell(Lookup("a"), probe.ref)
probe.expectMsgType[Bindings].services.map(_.path.name) should be(Set("a1"))
}
enterBarrier("after-5")
}
"replicate many service entries" in within(10.seconds) {
for (i ← 100 until 200) {
val service = system.actorOf(Props[Service], name = myself.name + "_" + i)
registry ! Register("a" + i, service)
}
awaitAssert {
val probe = TestProbe()
for (i ← 100 until 200) {
registry.tell(Lookup("a" + i), probe.ref)
probe.expectMsgType[Bindings].services.map(_.path.name) should be(roles.map(_.name + "_" + i).toSet)
}
}
enterBarrier("after-6")
}
}
}

184
akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/VotingContestSpec.scala
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@ -1,184 +0,0 @@
/**
* Copyright (C) 2009-2015 Typesafe Inc. <http://www.typesafe.com>
*/
package sample.datareplication
import scala.concurrent.duration._
import akka.actor.Actor
import akka.actor.ActorRef
import akka.actor.Props
import akka.cluster.Cluster
import akka.cluster.ddata.DistributedData
import akka.cluster.ddata.Flag
import akka.cluster.ddata.PNCounterMap
import akka.cluster.ddata.Replicator.GetReplicaCount
import akka.cluster.ddata.Replicator.ReplicaCount
import akka.cluster.ddata.STMultiNodeSpec
import akka.remote.testconductor.RoleName
import akka.remote.testkit.MultiNodeConfig
import akka.remote.testkit.MultiNodeSpec
import akka.testkit._
import com.typesafe.config.ConfigFactory
import akka.cluster.ddata.FlagKey
import akka.cluster.ddata.PNCounterMapKey
object VotingContestSpec extends MultiNodeConfig {
val node1 = role("node-1")
val node2 = role("node-2")
val node3 = role("node-3")
commonConfig(ConfigFactory.parseString("""
akka.loglevel = INFO
akka.actor.provider = "akka.cluster.ClusterActorRefProvider"
akka.log-dead-letters-during-shutdown = off
"""))
}
object VotingService {
case object Open
case object OpenAck
case object Close
case object CloseAck
final case class Vote(participant: String)
case object GetVotes
final case class Votes(result: Map[String, BigInt], open: Boolean)
private final case class GetVotesReq(replyTo: ActorRef)
}
class VotingService extends Actor {
import akka.cluster.ddata.Replicator._
import VotingService._
val replicator = DistributedData(context.system).replicator
implicit val cluster = Cluster(context.system)
val OpenedKey = FlagKey("contestOpened")
val ClosedKey = FlagKey("contestClosed")
val CountersKey = PNCounterMapKey("contestCounters")
replicator ! Subscribe(OpenedKey, self)
def receive = {
case Open ⇒
replicator ! Update(OpenedKey, Flag(), WriteAll(5.seconds))(_.switchOn)
becomeOpen()
case c @ Changed(OpenedKey) if c.get(OpenedKey).enabled ⇒
becomeOpen()
case GetVotes ⇒
sender() ! Votes(Map.empty, open = false)
}
def becomeOpen(): Unit = {
replicator ! Unsubscribe(OpenedKey, self)
replicator ! Subscribe(ClosedKey, self)
context.become(open orElse getVotes(open = true))
}
def open: Receive = {
case v @ Vote(participant) ⇒
val update = Update(CountersKey, PNCounterMap(), WriteLocal, request = Some(v)) {
_.increment(participant, 1)
}
replicator ! update
case _: UpdateSuccess[_] ⇒
case Close ⇒
replicator ! Update(ClosedKey, Flag(), WriteAll(5.seconds))(_.switchOn)
context.become(getVotes(open = false))
case c @ Changed(ClosedKey) if c.get(ClosedKey).enabled ⇒
context.become(getVotes(open = false))
}
def getVotes(open: Boolean): Receive = {
case GetVotes ⇒
replicator ! Get(CountersKey, ReadAll(3.seconds), Some(GetVotesReq(sender())))
case g @ GetSuccess(CountersKey, Some(GetVotesReq(replyTo))) ⇒
val data = g.get(CountersKey)
replyTo ! Votes(data.entries, open)
case NotFound(CountersKey, Some(GetVotesReq(replyTo))) ⇒
replyTo ! Votes(Map.empty, open)
case _: GetFailure[_] ⇒
case _: UpdateSuccess[_] ⇒
}
}
class VotingContestSpecMultiJvmNode1 extends VotingContestSpec
class VotingContestSpecMultiJvmNode2 extends VotingContestSpec
class VotingContestSpecMultiJvmNode3 extends VotingContestSpec
class VotingContestSpec extends MultiNodeSpec(VotingContestSpec) with STMultiNodeSpec with ImplicitSender {
import VotingContestSpec._
override def initialParticipants = roles.size
val cluster = Cluster(system)
def join(from: RoleName, to: RoleName): Unit = {
runOn(from) {
cluster join node(to).address
}
enterBarrier(from.name + "-joined")
}
"Demo of a replicated voting" must {
"join cluster" in within(10.seconds) {
join(node1, node1)
join(node2, node1)
join(node3, node1)
awaitAssert {
DistributedData(system).replicator ! GetReplicaCount
expectMsg(ReplicaCount(roles.size))
}
enterBarrier("after-1")
}
"count votes correctly" in within(15.seconds) {
import VotingService._
val votingService = system.actorOf(Props[VotingService], "votingService")
val N = 1000
runOn(node1) {
votingService ! Open
for (n ← 1 to N) {
votingService ! Vote("#" + ((n % 20) + 1))
}
}
runOn(node2, node3) {
// wait for it to open
val p = TestProbe()
awaitAssert {
votingService.tell(GetVotes, p.ref)
p.expectMsgPF(3.seconds) { case Votes(_, true) ⇒ true }
}
for (n ← 1 to N) {
votingService ! Vote("#" + ((n % 20) + 1))
}
}
enterBarrier("voting-done")
runOn(node3) {
votingService ! Close
}
val expected = (1 to 20).map(n ⇒ "#" + n -> BigInt(3L * N / 20)).toMap
awaitAssert {
votingService ! GetVotes
expectMsg(3.seconds, Votes(expected, false))
}
enterBarrier("after-2")
}
}
}

17
akka-distributed-data/src/test/scala/akka/cluster/ddata/sample/LotsOfDataBot.scala → akka-distributed-data/src/test/scala/akka/cluster/ddata/LotsOfDataBot.scala
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@ -1,7 +1,7 @@
/** /**
* Copyright (C) 2015 Typesafe Inc. <http://www.typesafe.com> * Copyright (C) 2015 Typesafe Inc. <http://www.typesafe.com>
*/ */
package akka.cluster.ddata.sample package akka.cluster.ddata
import scala.concurrent.duration._ import scala.concurrent.duration._
import scala.concurrent.forkjoin.ThreadLocalRandom import scala.concurrent.forkjoin.ThreadLocalRandom
@ -10,12 +10,19 @@ import akka.actor.ActorLogging
import akka.actor.ActorSystem import akka.actor.ActorSystem
import akka.actor.Props import akka.actor.Props
import akka.cluster.Cluster import akka.cluster.Cluster
import akka.cluster.ddata.DistributedData import akka.cluster.ddata.Replicator.Changed
import akka.cluster.ddata.ORSet import akka.cluster.ddata.Replicator.GetKeyIds
import akka.cluster.ddata.Replicator.GetKeyIdsResult
import akka.cluster.ddata.Replicator.Subscribe
import akka.cluster.ddata.Replicator.Update
import akka.cluster.ddata.Replicator.UpdateResponse
import akka.cluster.ddata.Replicator.WriteLocal
import com.typesafe.config.ConfigFactory import com.typesafe.config.ConfigFactory
import akka.cluster.ddata.Replicator
import akka.cluster.ddata.ORSetKey
/**
* This "sample" simulates lots of data entries, and can be used for
* optimizing replication (e.g. catch-up when adding more nodes).
*/
object LotsOfDataBot { object LotsOfDataBot {
def main(args: Array[String]): Unit = { def main(args: Array[String]): Unit = {

98
akka-distributed-data/src/test/scala/akka/cluster/ddata/sample/DataBot.scala
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@ -1,98 +0,0 @@
/**
* Copyright (C) 2015 Typesafe Inc. <http://www.typesafe.com>
*/
package akka.cluster.ddata.sample
import scala.concurrent.duration._
import scala.concurrent.forkjoin.ThreadLocalRandom
import akka.actor.Actor
import akka.actor.ActorLogging
import akka.actor.ActorSystem
import akka.actor.Props
import akka.cluster.Cluster
import akka.cluster.ddata.DistributedData
import akka.cluster.ddata.ORSet
import com.typesafe.config.ConfigFactory
import akka.cluster.ddata.Replicator
import akka.cluster.ddata.ORSetKey
object DataBot {
def main(args: Array[String]): Unit = {
if (args.isEmpty)
startup(Seq("2551", "2552", "0"))
else
startup(args)
}
def startup(ports: Seq[String]): Unit = {
ports.foreach { port ⇒
// Override the configuration of the port
val config = ConfigFactory.parseString("akka.remote.netty.tcp.port=" + port).
withFallback(ConfigFactory.load(
ConfigFactory.parseString("""
akka.actor.provider = "akka.cluster.ClusterActorRefProvider"
akka.remote {
netty.tcp {
hostname = "127.0.0.1"
port = 0
}
}
akka.cluster {
seed-nodes = [
"akka.tcp://ClusterSystem@127.0.0.1:2551",
"akka.tcp://ClusterSystem@127.0.0.1:2552"]
auto-down-unreachable-after = 10s
}
""")))
// Create an Akka system
val system = ActorSystem("ClusterSystem", config)
// Create an actor that handles cluster domain events
system.actorOf(Props[DataBot], name = "dataBot")
}
}
private case object Tick
}
class DataBot extends Actor with ActorLogging {
import DataBot._
import Replicator._
val replicator = DistributedData(context.system).replicator
implicit val node = Cluster(context.system)
import context.dispatcher
val tickTask = context.system.scheduler.schedule(5.seconds, 5.seconds, self, Tick)
val DataKey = ORSetKey[String]("key")
replicator ! Subscribe(DataKey, self)
def receive = {
case Tick ⇒
val s = ThreadLocalRandom.current().nextInt(97, 123).toChar.toString
if (ThreadLocalRandom.current().nextBoolean()) {
// add
log.info("Adding: {}", s)
replicator ! Update(DataKey, ORSet.empty[String], WriteLocal)(_ + s)
} else {
// remove
log.info("Removing: {}", s)
replicator ! Update(DataKey, ORSet.empty[String], WriteLocal)(_ - s)
}
case _: UpdateResponse[_] ⇒ // ignore
case c @ Changed(DataKey) ⇒
log.info("Current elements: {}", c.get(DataKey).elements)
}
override def postStop(): Unit = tickTask.cancel()
}

25
akka-docs/rst/java/distributed-data.rst
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@ -178,11 +178,11 @@ Here is an example of using ``writeMajority`` and ``readMajority``:
**FIXME convert this example to Java** **FIXME convert this example to Java**
.. includecode:: ../../../akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedShoppingCartSpec.scala#read-write-majority .. includecode:: ../../../akka-samples/akka-sample-distributed-data-scala/src/main/scala/sample/distributeddata/ShoppingCart.scala#read-write-majority
.. includecode:: ../../../akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedShoppingCartSpec.scala#get-cart .. includecode:: ../../../akka-samples/akka-sample-distributed-data-scala/src/main/scala/sample/distributeddata/ShoppingCart.scala#get-cart
.. includecode:: ../../../akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedShoppingCartSpec.scala#add-item .. includecode:: ../../../akka-samples/akka-sample-distributed-data-scala/src/main/scala/sample/distributeddata/ShoppingCart.scala#add-item
In some rare cases, when performing an ``Update`` it is needed to first try to fetch latest data from In some rare cases, when performing an ``Update`` it is needed to first try to fetch latest data from
other nodes. That can be done by first sending a ``Get`` with ``ReadMajority`` and then continue with other nodes. That can be done by first sending a ``Get`` with ``ReadMajority`` and then continue with
@ -196,7 +196,7 @@ The following example illustrates how to do that:
**FIXME convert this example to Java** **FIXME convert this example to Java**
.. includecode:: ../../../akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedShoppingCartSpec.scala#remove-item .. includecode:: ../../../akka-samples/akka-sample-distributed-data-scala/src/main/scala/sample/distributeddata/ShoppingCart.scala#remove-item
.. warning:: .. warning::
@ -333,7 +333,7 @@ use a timestamp value based on something else, for example an increasing version
from a database record that is used for optimistic concurrency control. from a database record that is used for optimistic concurrency control.
When a data entry is changed the full state of that entry is replicated to other nodes, i.e. When a data entry is changed the full state of that entry is replicated to other nodes, i.e.
when you update an map the whole map is replicated. Therefore, instead of using one ``ORMap`` when you update a map the whole map is replicated. Therefore, instead of using one ``ORMap``
with 1000 elements it is more efficient to split that up in 10 top level ``ORMap`` entries with 1000 elements it is more efficient to split that up in 10 top level ``ORMap`` entries
with 100 elements each. Top level entries are replicated individually, which has the with 100 elements each. Top level entries are replicated individually, which has the
trade-off that different entries may not be replicated at the same time and you may see trade-off that different entries may not be replicated at the same time and you may see
@ -454,13 +454,16 @@ cluster. Data types that need pruning have to implement the ``RemovedNodePruning
Samples Samples
======= =======
**FIXME convert these sampes to Java and activator template** **FIXME convert these sampes to Java**
* `Replicated Cache <@github@/akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedCacheSpec.scala>`_ Several interesting samples are included and described in the `Typesafe Activator <http://www.typesafe.com/platform/getstarted>`_
* `Replicated Metrics <@github@/akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedMetricsSpec.scala>`_ tutorial named `Akka Distributed Data Samples with Scala <http://www.typesafe.com/activator/template/akka-sample-distributed-data-scala>`_.
* `Replicated Service Registry <@github@/akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedServiceRegistrySpec.scala>`_
* `VotingService <@github@/akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/VotingContestSpec.scala>`_ * Low Latency Voting Service
* `ShoppingCart <@github@/akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedShoppingCartSpec.scala>`_ * Highly Available Shopping Cart
* Distributed Service Registry
* Replicated Cache
* Replicated Metrics
Limitations Limitations
=========== ===========

23
akka-docs/rst/scala/distributed-data.rst
View file

@ -176,11 +176,11 @@ to 4 nodes and reads from 4 nodes.
Here is an example of using ``WriteMajority`` and ``ReadMajority``: Here is an example of using ``WriteMajority`` and ``ReadMajority``:
.. includecode:: ../../../akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedShoppingCartSpec.scala#read-write-majority .. includecode:: ../../../akka-samples/akka-sample-distributed-data-scala/src/main/scala/sample/distributeddata/ShoppingCart.scala#read-write-majority
.. includecode:: ../../../akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedShoppingCartSpec.scala#get-cart .. includecode:: ../../../akka-samples/akka-sample-distributed-data-scala/src/main/scala/sample/distributeddata/ShoppingCart.scala#get-cart
.. includecode:: ../../../akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedShoppingCartSpec.scala#add-item .. includecode:: ../../../akka-samples/akka-sample-distributed-data-scala/src/main/scala/sample/distributeddata/ShoppingCart.scala#add-item
In some rare cases, when performing an ``Update`` it is needed to first try to fetch latest data from In some rare cases, when performing an ``Update`` it is needed to first try to fetch latest data from
other nodes. That can be done by first sending a ``Get`` with ``ReadMajority`` and then continue with other nodes. That can be done by first sending a ``Get`` with ``ReadMajority`` and then continue with
@ -192,7 +192,7 @@ performed (hence the name observed-removed set).
The following example illustrates how to do that: The following example illustrates how to do that:
.. includecode:: ../../../akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedShoppingCartSpec.scala#remove-item .. includecode:: ../../../akka-samples/akka-sample-distributed-data-scala/src/main/scala/sample/distributeddata/ShoppingCart.scala#remove-item
.. warning:: .. warning::
@ -329,7 +329,7 @@ use a timestamp value based on something else, for example an increasing version
from a database record that is used for optimistic concurrency control. from a database record that is used for optimistic concurrency control.
When a data entry is changed the full state of that entry is replicated to other nodes, i.e. When a data entry is changed the full state of that entry is replicated to other nodes, i.e.
when you update an map the whole map is replicated. Therefore, instead of using one ``ORMap`` when you update a map the whole map is replicated. Therefore, instead of using one ``ORMap``
with 1000 elements it is more efficient to split that up in 10 top level ``ORMap`` entries with 1000 elements it is more efficient to split that up in 10 top level ``ORMap`` entries
with 100 elements each. Top level entries are replicated individually, which has the with 100 elements each. Top level entries are replicated individually, which has the
trade-off that different entries may not be replicated at the same time and you may see trade-off that different entries may not be replicated at the same time and you may see
@ -442,13 +442,14 @@ cluster. Data types that need pruning have to implement the ``RemovedNodePruning
Samples Samples
======= =======
**FIXME convert these samples to activator template** Several interesting samples are included and described in the `Typesafe Activator <http://www.typesafe.com/platform/getstarted>`_
tutorial named `Akka Distributed Data Samples with Scala <http://www.typesafe.com/activator/template/akka-sample-distributed-data-scala>`_.
* `Replicated Cache <@github@/akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedCacheSpec.scala>`_ * Low Latency Voting Service
* `Replicated Metrics <@github@/akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedMetricsSpec.scala>`_ * Highly Available Shopping Cart
* `Replicated Service Registry <@github@/akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedServiceRegistrySpec.scala>`_ * Distributed Service Registry
* `VotingService <@github@/akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/VotingContestSpec.scala>`_ * Replicated Cache
* `ShoppingCart <@github@/akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedShoppingCartSpec.scala>`_ * Replicated Metrics
Limitations Limitations
=========== ===========

17
akka-samples/akka-sample-distributed-data-scala/.gitignore vendored Normal file
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@ -0,0 +1,17 @@
*#
*.iml
*.ipr
*.iws
*.pyc
*.tm.epoch
*.vim
*-shim.sbt
.idea/
/project/plugins/project
project/boot
target/
/logs
.cache
.classpath
.project
.settings

121
akka-samples/akka-sample-distributed-data-scala/COPYING Normal file
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@ -0,0 +1,121 @@
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10
akka-samples/akka-sample-distributed-data-scala/LICENSE Normal file
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@ -0,0 +1,10 @@
Activator Template by Typesafe
Licensed under Public Domain (CC0)
To the extent possible under law, the person who associated CC0 with
this Activator Tempate has waived all copyright and related or neighboring
rights to this Activator Template.
You should have received a copy of the CC0 legalcode along with this
work. If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.

7
akka-samples/akka-sample-distributed-data-scala/activator.properties Normal file
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@ -0,0 +1,7 @@
name=akka-sample-distributed-data-scala
title=Akka Distributed Data Samples with Scala
description=Akka Distributed Data Samples with Scala
tags=akka,cluster,scala,sample,distributed-data
authorName=Akka Team
authorLink=http://akka.io/
sourceLink=https://github.com/akka/akka

46
akka-samples/akka-sample-distributed-data-scala/build.sbt Normal file
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@ -0,0 +1,46 @@
import com.typesafe.sbt.SbtMultiJvm
import com.typesafe.sbt.SbtMultiJvm.MultiJvmKeys.MultiJvm
val akkaVersion = "2.4-SNAPSHOT"
val project = Project(
id = "akka-sample-distributed-data-scala",
base = file("."),
settings = Project.defaultSettings ++ SbtMultiJvm.multiJvmSettings ++ Seq(
name := "akka-sample-distributed-data-scala",
version := "2.4-SNAPSHOT",
scalaVersion := "2.11.6",
scalacOptions in Compile ++= Seq("-encoding", "UTF-8", "-target:jvm-1.8", "-deprecation", "-feature", "-unchecked", "-Xlog-reflective-calls", "-Xlint"),
javacOptions in Compile ++= Seq("-source", "1.8", "-target", "1.8", "-Xlint:unchecked", "-Xlint:deprecation"),
libraryDependencies ++= Seq(
"com.typesafe.akka" %% "akka-actor" % akkaVersion,
"com.typesafe.akka" %% "akka-remote" % akkaVersion,
"com.typesafe.akka" %% "akka-cluster" % akkaVersion,
"com.typesafe.akka" %% "akka-distributed-data-experimental" % akkaVersion,
"com.typesafe.akka" %% "akka-multi-node-testkit" % akkaVersion,
"org.scalatest" %% "scalatest" % "2.2.1" % "test"),
javaOptions in run ++= Seq(
"-Xms128m", "-Xmx1024m"),
Keys.fork in run := true,
// make sure that MultiJvm test are compiled by the default test compilation
compile in MultiJvm <<= (compile in MultiJvm) triggeredBy (compile in Test),
// disable parallel tests
parallelExecution in Test := false,
// make sure that MultiJvm tests are executed by the default test target,
// and combine the results from ordinary test and multi-jvm tests
executeTests in Test <<= (executeTests in Test, executeTests in MultiJvm) map {
case (testResults, multiNodeResults) =>
val overall =
if (testResults.overall.id < multiNodeResults.overall.id)
multiNodeResults.overall
else
testResults.overall
Tests.Output(overall,
testResults.events ++ multiNodeResults.events,
testResults.summaries ++ multiNodeResults.summaries)
}
)
) configs (MultiJvm)
fork in run := true

1
akka-samples/akka-sample-distributed-data-scala/project/build.properties Normal file
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@ -0,0 +1 @@
sbt.version=0.13.7

4
akka-samples/akka-sample-distributed-data-scala/project/plugins.sbt Normal file
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@ -0,0 +1,4 @@
resolvers += Classpaths.typesafeResolver
addSbtPlugin("com.typesafe.sbt" % "sbt-multi-jvm" % "0.3.8")

3
akka-samples/akka-sample-distributed-data-scala/project/sbt-ui.sbt Normal file
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@ -0,0 +1,3 @@
// This plugin represents functionality that is to be added to sbt in the future
addSbtPlugin("org.scala-sbt" % "sbt-core-next" % "0.1.1")

21
akka-samples/akka-sample-distributed-data-scala/src/main/resources/application.conf Normal file
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@ -0,0 +1,21 @@
akka {
actor {
provider = "akka.cluster.ClusterActorRefProvider"
}
remote {
log-remote-lifecycle-events = off
netty.tcp {
hostname = "127.0.0.1"
port = 0
}
}
cluster {
seed-nodes = [
"akka.tcp://ClusterSystem@127.0.0.1:2551",
"akka.tcp://ClusterSystem@127.0.0.1:2552"]
auto-down-unreachable-after = 10s
}
}

53
akka-samples/akka-sample-distributed-data-scala/src/main/scala/sample/distributeddata/ReplicatedCache.scala Normal file
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@ -0,0 +1,53 @@
package sample.distributeddata
import akka.actor.Actor
import akka.actor.ActorRef
import akka.actor.Props
import akka.cluster.Cluster
import akka.cluster.ddata.DistributedData
import akka.cluster.ddata.LWWMap
import akka.cluster.ddata.LWWMapKey
object ReplicatedCache {
import akka.cluster.ddata.Replicator._
def props: Props = Props[ReplicatedCache]
private final case class Request(key: String, replyTo: ActorRef)
final case class PutInCache(key: String, value: Any)
final case class GetFromCache(key: String)
final case class Cached(key: String, value: Option[Any])
final case class Evict(key: String)
}
class ReplicatedCache extends Actor {
import akka.cluster.ddata.Replicator._
import ReplicatedCache._
val replicator = DistributedData(context.system).replicator
implicit val cluster = Cluster(context.system)
def dataKey(entryKey: String): LWWMapKey[Any] =
LWWMapKey("cache-" + math.abs(entryKey.hashCode) % 100)
def receive = {
case PutInCache(key, value) ⇒
replicator ! Update(dataKey(key), LWWMap(), WriteLocal)(_ + (key -> value))
case Evict(key) ⇒
replicator ! Update(dataKey(key), LWWMap(), WriteLocal)(_ - key)
case GetFromCache(key) ⇒
replicator ! Get(dataKey(key), ReadLocal, Some(Request(key, sender())))
case g @ GetSuccess(LWWMapKey(_), Some(Request(key, replyTo))) ⇒
g.dataValue match {
case data: LWWMap[_] ⇒ data.get(key) match {
case Some(value) ⇒ replyTo ! Cached(key, Some(value))
case None ⇒ replyTo ! Cached(key, None)
}
}
case NotFound(_, Some(Request(key, replyTo))) ⇒
replyTo ! Cached(key, None)
case _: UpdateResponse[_] ⇒ // ok
}
}

97
akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedMetricsSpec.scala → akka-samples/akka-sample-distributed-data-scala/src/main/scala/sample/distributeddata/ReplicatedMetrics.scala
View file

@ -1,42 +1,21 @@
/** package sample.distributeddata
* Copyright (C) 2009-2015 Typesafe Inc. <http://www.typesafe.com>
*/
package sample.datareplication
import java.lang.management.ManagementFactory import java.lang.management.ManagementFactory
import java.lang.management.MemoryMXBean import java.lang.management.MemoryMXBean
import scala.concurrent.duration._ import scala.concurrent.duration._
import scala.concurrent.duration.FiniteDuration
import akka.actor.Actor import akka.actor.Actor
import akka.actor.ActorLogging import akka.actor.ActorLogging
import akka.actor.Address import akka.actor.Address
import akka.actor.Props import akka.actor.Props
import akka.cluster.Cluster import akka.cluster.Cluster
import akka.cluster.ClusterEvent.{ InitialStateAsEvents, MemberUp, MemberRemoved } import akka.cluster.ClusterEvent.InitialStateAsEvents
import akka.cluster.ClusterEvent.MemberRemoved
import akka.cluster.ClusterEvent.MemberUp
import akka.cluster.ddata.DistributedData import akka.cluster.ddata.DistributedData
import akka.cluster.ddata.LWWMap import akka.cluster.ddata.LWWMap
import akka.cluster.ddata.Replicator.GetReplicaCount
import akka.cluster.ddata.Replicator.ReplicaCount
import akka.cluster.ddata.STMultiNodeSpec
import akka.remote.testconductor.RoleName
import akka.remote.testkit.MultiNodeConfig
import akka.remote.testkit.MultiNodeSpec
import akka.testkit._
import com.typesafe.config.ConfigFactory
import akka.cluster.ddata.LWWMapKey import akka.cluster.ddata.LWWMapKey
object ReplicatedMetricsSpec extends MultiNodeConfig {
val node1 = role("node-1")
val node2 = role("node-2")
val node3 = role("node-3")
commonConfig(ConfigFactory.parseString("""
akka.loglevel = INFO
akka.actor.provider = "akka.cluster.ClusterActorRefProvider"
akka.log-dead-letters-during-shutdown = off
"""))
}
object ReplicatedMetrics { object ReplicatedMetrics {
import akka.cluster.ddata.Replicator._ import akka.cluster.ddata.Replicator._
@ -132,69 +111,3 @@ class ReplicatedMetrics(measureInterval: FiniteDuration, cleanupInterval: Finite
} }
} }
class ReplicatedMetricsSpecMultiJvmNode1 extends ReplicatedMetricsSpec
class ReplicatedMetricsSpecMultiJvmNode2 extends ReplicatedMetricsSpec
class ReplicatedMetricsSpecMultiJvmNode3 extends ReplicatedMetricsSpec
class ReplicatedMetricsSpec extends MultiNodeSpec(ReplicatedMetricsSpec) with STMultiNodeSpec with ImplicitSender {
import ReplicatedMetricsSpec._
import ReplicatedMetrics._
override def initialParticipants = roles.size
val cluster = Cluster(system)
val replicatedMetrics = system.actorOf(ReplicatedMetrics.props(1.second, 3.seconds))
def join(from: RoleName, to: RoleName): Unit = {
runOn(from) {
cluster join node(to).address
}
enterBarrier(from.name + "-joined")
}
"Demo of a replicated metrics" must {
"join cluster" in within(10.seconds) {
join(node1, node1)
join(node2, node1)
join(node3, node1)
awaitAssert {
DistributedData(system).replicator ! GetReplicaCount
expectMsg(ReplicaCount(roles.size))
}
enterBarrier("after-1")
}
"replicate metrics" in within(10.seconds) {
val probe = TestProbe()
system.eventStream.subscribe(probe.ref, classOf[UsedHeap])
awaitAssert {
probe.expectMsgType[UsedHeap].percentPerNode.size should be(3)
}
probe.expectMsgType[UsedHeap].percentPerNode.size should be(3)
probe.expectMsgType[UsedHeap].percentPerNode.size should be(3)
enterBarrier("after-2")
}
"cleanup removed node" in within(15.seconds) {
val node3Address = node(node3).address
runOn(node1) {
cluster.leave(node3Address)
}
runOn(node1, node2) {
val probe = TestProbe()
system.eventStream.subscribe(probe.ref, classOf[UsedHeap])
awaitAssert {
probe.expectMsgType[UsedHeap].percentPerNode.size should be(2)
}
probe.expectMsgType[UsedHeap].percentPerNode should not contain (
nodeKey(node3Address))
}
enterBarrier("after-3")
}
}
}

127
akka-samples/akka-sample-distributed-data-scala/src/main/scala/sample/distributeddata/ServiceRegistry.scala Normal file
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@ -0,0 +1,127 @@
package sample.distributeddata
import akka.actor.Actor
import akka.actor.ActorLogging
import akka.actor.ActorRef
import akka.actor.Props
import akka.actor.Terminated
import akka.cluster.Cluster
import akka.cluster.ClusterEvent
import akka.cluster.ClusterEvent.LeaderChanged
import akka.cluster.ddata.DistributedData
import akka.cluster.ddata.GSet
import akka.cluster.ddata.GSetKey
import akka.cluster.ddata.Key
import akka.cluster.ddata.ORSet
object ServiceRegistry {
import akka.cluster.ddata.Replicator._
val props: Props = Props[ServiceRegistry]
/**
* Register a `service` with a `name`. Several services
* can be registered with the same `name`.
* It will be removed when it is terminated.
*/
final case class Register(name: String, service: ActorRef)
/**
* Lookup services registered for a `name`. [[Bindings]] will
* be sent to `sender()`.
*/
final case class Lookup(name: String)
/**
* Reply for [[Lookup]]
*/
final case class Bindings(name: String, services: Set[ActorRef])
/**
* Published to `System.eventStream` when services are changed.
*/
final case class BindingChanged(name: String, services: Set[ActorRef])
final case class ServiceKey(serviceName: String) extends Key[ORSet[ActorRef]](serviceName)
private val AllServicesKey = GSetKey[ServiceKey]("service-keys")
}
class ServiceRegistry extends Actor with ActorLogging {
import akka.cluster.ddata.Replicator._
import ServiceRegistry._
val replicator = DistributedData(context.system).replicator
implicit val cluster = Cluster(context.system)
var keys = Set.empty[ServiceKey]
var services = Map.empty[String, Set[ActorRef]]
var leader = false
def serviceKey(serviceName: String): ServiceKey =
ServiceKey("service:" + serviceName)
override def preStart(): Unit = {
replicator ! Subscribe(AllServicesKey, self)
cluster.subscribe(self, ClusterEvent.InitialStateAsEvents, classOf[ClusterEvent.LeaderChanged])
}
override def postStop(): Unit = {
cluster.unsubscribe(self)
}
def receive = {
case Register(name, service) ⇒
val dKey = serviceKey(name)
// store the service names in a separate GSet to be able to
// get notifications of new names
if (!keys(dKey))
replicator ! Update(AllServicesKey, GSet(), WriteLocal)(_ + dKey)
// add the service
replicator ! Update(dKey, ORSet(), WriteLocal)(_ + service)
case Lookup(key) ⇒
sender() ! Bindings(key, services.getOrElse(key, Set.empty))
case c @ Changed(AllServicesKey) ⇒
val newKeys = c.get(AllServicesKey).elements
log.debug("Services changed, added: {}, all: {}", (newKeys -- keys), newKeys)
(newKeys -- keys).foreach { dKey ⇒
// subscribe to get notifications of when services with this name are added or removed
replicator ! Subscribe(dKey, self)
}
keys = newKeys
case c @ Changed(ServiceKey(serviceName)) ⇒
val name = serviceName.split(":").tail.mkString
val newServices = c.get(serviceKey(name)).elements
log.debug("Services changed for name [{}]: {}", name, newServices)
services = services.updated(name, newServices)
context.system.eventStream.publish(BindingChanged(name, newServices))
if (leader)
newServices.foreach(context.watch) // watch is idempotent
case LeaderChanged(node) ⇒
// Let one node (the leader) be responsible for removal of terminated services
// to avoid redundant work and too many death watch notifications.
// It is not critical to only do it from one node.
val wasLeader = leader
leader = node.exists(_ == cluster.selfAddress)
// when used with many (> 500) services you must increase the system message buffer
// `akka.remote.system-message-buffer-size`
if (!wasLeader && leader)
for (refs ← services.valuesIterator; ref ← refs)
context.watch(ref)
else if (wasLeader && !leader)
for (refs ← services.valuesIterator; ref ← refs)
context.unwatch(ref)
case Terminated(ref) ⇒
val names = services.collect { case (name, refs) if refs.contains(ref) ⇒ name }
names.foreach { name ⇒
log.debug("Service with name [{}] terminated: {}", name, ref)
replicator ! Update(serviceKey(name), ORSet(), WriteLocal)(_ - ref)
}
case _: UpdateResponse[_] ⇒ // ok
}
}

99
akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedShoppingCartSpec.scala → akka-samples/akka-sample-distributed-data-scala/src/main/scala/sample/distributeddata/ShoppingCart.scala
View file

@ -1,7 +1,4 @@
/** package sample.distributeddata
* Copyright (C) 2009-2015 Typesafe Inc. <http://www.typesafe.com>
*/
package sample.datareplication
import scala.concurrent.duration._ import scala.concurrent.duration._
import akka.actor.Actor import akka.actor.Actor
@ -10,29 +7,8 @@ import akka.actor.Props
import akka.cluster.Cluster import akka.cluster.Cluster
import akka.cluster.ddata.DistributedData import akka.cluster.ddata.DistributedData
import akka.cluster.ddata.LWWMap import akka.cluster.ddata.LWWMap
import akka.cluster.ddata.Replicator.GetReplicaCount
import akka.cluster.ddata.Replicator.ReplicaCount
import akka.cluster.ddata.STMultiNodeSpec
import akka.remote.testconductor.RoleName
import akka.remote.testkit.MultiNodeConfig
import akka.remote.testkit.MultiNodeSpec
import akka.testkit._
import com.typesafe.config.ConfigFactory
import akka.cluster.ddata.LWWMapKey import akka.cluster.ddata.LWWMapKey
object ReplicatedShoppingCartSpec extends MultiNodeConfig {
val node1 = role("node-1")
val node2 = role("node-2")
val node3 = role("node-3")
commonConfig(ConfigFactory.parseString("""
akka.loglevel = INFO
akka.actor.provider = "akka.cluster.ClusterActorRefProvider"
akka.log-dead-letters-during-shutdown = off
"""))
}
object ShoppingCart { object ShoppingCart {
import akka.cluster.ddata.Replicator._ import akka.cluster.ddata.Replicator._
@ -139,76 +115,3 @@ class ShoppingCart(userId: String) extends Actor {
} }
} }
class ReplicatedShoppingCartSpecMultiJvmNode1 extends ReplicatedShoppingCartSpec
class ReplicatedShoppingCartSpecMultiJvmNode2 extends ReplicatedShoppingCartSpec
class ReplicatedShoppingCartSpecMultiJvmNode3 extends ReplicatedShoppingCartSpec
class ReplicatedShoppingCartSpec extends MultiNodeSpec(ReplicatedShoppingCartSpec) with STMultiNodeSpec with ImplicitSender {
import ReplicatedShoppingCartSpec._
import ShoppingCart._
override def initialParticipants = roles.size
val cluster = Cluster(system)
val shoppingCart = system.actorOf(ShoppingCart.props("user-1"))
def join(from: RoleName, to: RoleName): Unit = {
runOn(from) {
cluster join node(to).address
}
enterBarrier(from.name + "-joined")
}
"Demo of a replicated shopping cart" must {
"join cluster" in within(10.seconds) {
join(node1, node1)
join(node2, node1)
join(node3, node1)
awaitAssert {
DistributedData(system).replicator ! GetReplicaCount
expectMsg(ReplicaCount(roles.size))
}
enterBarrier("after-1")
}
"handle updates directly after start" in within(15.seconds) {
runOn(node2) {
shoppingCart ! ShoppingCart.AddItem(LineItem("1", "Apples", quantity = 2))
shoppingCart ! ShoppingCart.AddItem(LineItem("2", "Oranges", quantity = 3))
}
enterBarrier("updates-done")
awaitAssert {
shoppingCart ! ShoppingCart.GetCart
val cart = expectMsgType[Cart]
cart.items should be(Set(LineItem("1", "Apples", quantity = 2), LineItem("2", "Oranges", quantity = 3)))
}
enterBarrier("after-2")
}
"handle updates from different nodes" in within(5.seconds) {
runOn(node2) {
shoppingCart ! ShoppingCart.AddItem(LineItem("1", "Apples", quantity = 5))
shoppingCart ! ShoppingCart.RemoveItem("2")
}
runOn(node3) {
shoppingCart ! ShoppingCart.AddItem(LineItem("3", "Bananas", quantity = 4))
}
enterBarrier("updates-done")
awaitAssert {
shoppingCart ! ShoppingCart.GetCart
val cart = expectMsgType[Cart]
cart.items should be(Set(LineItem("1", "Apples", quantity = 7), LineItem("3", "Bananas", quantity = 4)))
}
enterBarrier("after-3")
}
}
}

88
akka-samples/akka-sample-distributed-data-scala/src/main/scala/sample/distributeddata/VotingService.scala Normal file
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@ -0,0 +1,88 @@
package sample.distributeddata
import scala.concurrent.duration._
import akka.cluster.ddata.DistributedData
import akka.cluster.ddata.FlagKey
import akka.actor.Actor
import akka.cluster.ddata.PNCounterMapKey
import akka.actor.ActorRef
import akka.cluster.Cluster
import akka.cluster.ddata.PNCounterMap
import akka.cluster.ddata.Flag
object VotingService {
case object Open
case object OpenAck
case object Close
case object CloseAck
final case class Vote(participant: String)
case object GetVotes
final case class Votes(result: Map[String, BigInt], open: Boolean)
private final case class GetVotesReq(replyTo: ActorRef)
}
class VotingService extends Actor {
import akka.cluster.ddata.Replicator._
import VotingService._
val replicator = DistributedData(context.system).replicator
implicit val cluster = Cluster(context.system)
val OpenedKey = FlagKey("contestOpened")
val ClosedKey = FlagKey("contestClosed")
val CountersKey = PNCounterMapKey("contestCounters")
replicator ! Subscribe(OpenedKey, self)
def receive = {
case Open ⇒
replicator ! Update(OpenedKey, Flag(), WriteAll(5.seconds))(_.switchOn)
becomeOpen()
case c @ Changed(OpenedKey) if c.get(OpenedKey).enabled ⇒
becomeOpen()
case GetVotes ⇒
sender() ! Votes(Map.empty, open = false)
}
def becomeOpen(): Unit = {
replicator ! Unsubscribe(OpenedKey, self)
replicator ! Subscribe(ClosedKey, self)
context.become(open orElse getVotes(open = true))
}
def open: Receive = {
case v @ Vote(participant) ⇒
val update = Update(CountersKey, PNCounterMap(), WriteLocal, request = Some(v)) {
_.increment(participant, 1)
}
replicator ! update
case _: UpdateSuccess[_] ⇒
case Close ⇒
replicator ! Update(ClosedKey, Flag(), WriteAll(5.seconds))(_.switchOn)
context.become(getVotes(open = false))
case c @ Changed(ClosedKey) if c.get(ClosedKey).enabled ⇒
context.become(getVotes(open = false))
}
def getVotes(open: Boolean): Receive = {
case GetVotes ⇒
replicator ! Get(CountersKey, ReadAll(3.seconds), Some(GetVotesReq(sender())))
case g @ GetSuccess(CountersKey, Some(GetVotesReq(replyTo))) ⇒
val data = g.get(CountersKey)
replyTo ! Votes(data.entries, open)
case NotFound(CountersKey, Some(GetVotesReq(replyTo))) ⇒
replyTo ! Votes(Map.empty, open)
case _: GetFailure[_] ⇒
case _: UpdateSuccess[_] ⇒
}
}

55
akka-distributed-data/src/multi-jvm/scala/sample/distributeddata/ReplicatedCacheSpec.scala → akka-samples/akka-sample-distributed-data-scala/src/multi-jvm/scala/sample/distributeddata/ReplicatedCacheSpec.scala
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@ -1,24 +1,15 @@
/** package sample.distributeddata
* Copyright (C) 2009-2015 Typesafe Inc. <http://www.typesafe.com>
*/
package sample.datareplication
import scala.concurrent.duration._ import scala.concurrent.duration._
import akka.actor.Actor
import akka.actor.ActorRef
import akka.actor.Props
import akka.cluster.Cluster import akka.cluster.Cluster
import akka.cluster.ddata.DistributedData import akka.cluster.ddata.DistributedData
import akka.cluster.ddata.LWWMap
import akka.cluster.ddata.Replicator.GetReplicaCount import akka.cluster.ddata.Replicator.GetReplicaCount
import akka.cluster.ddata.Replicator.ReplicaCount import akka.cluster.ddata.Replicator.ReplicaCount
import akka.cluster.ddata.STMultiNodeSpec
import akka.remote.testconductor.RoleName import akka.remote.testconductor.RoleName
import akka.remote.testkit.MultiNodeConfig import akka.remote.testkit.MultiNodeConfig
import akka.remote.testkit.MultiNodeSpec import akka.remote.testkit.MultiNodeSpec
import akka.testkit._ import akka.testkit._
import com.typesafe.config.ConfigFactory import com.typesafe.config.ConfigFactory
import akka.cluster.ddata.LWWMapKey
object ReplicatedCacheSpec extends MultiNodeConfig { object ReplicatedCacheSpec extends MultiNodeConfig {
val node1 = role("node-1") val node1 = role("node-1")
@ -33,50 +24,6 @@ object ReplicatedCacheSpec extends MultiNodeConfig {
} }
object ReplicatedCache {
import akka.cluster.ddata.Replicator._
def props: Props = Props[ReplicatedCache]
private final case class Request(key: String, replyTo: ActorRef)
final case class PutInCache(key: String, value: Any)
final case class GetFromCache(key: String)
final case class Cached(key: String, value: Option[Any])
final case class Evict(key: String)
}
class ReplicatedCache() extends Actor {
import akka.cluster.ddata.Replicator._
import ReplicatedCache._
val replicator = DistributedData(context.system).replicator
implicit val cluster = Cluster(context.system)
def dataKey(entryKey: String): LWWMapKey[Any] =
LWWMapKey("cache-" + math.abs(entryKey.hashCode) % 100)
def receive = {
case PutInCache(key, value) ⇒
replicator ! Update(dataKey(key), LWWMap(), WriteLocal)(_ + (key -> value))
case Evict(key) ⇒
replicator ! Update(dataKey(key), LWWMap(), WriteLocal)(_ - key)
case GetFromCache(key) ⇒
replicator ! Get(dataKey(key), ReadLocal, Some(Request(key, sender())))
case g @ GetSuccess(LWWMapKey(_), Some(Request(key, replyTo))) ⇒
g.dataValue match {
case data: LWWMap[_] ⇒ data.get(key) match {
case Some(value) ⇒ replyTo ! Cached(key, Some(value))
case None ⇒ replyTo ! Cached(key, None)
}
}
case NotFound(_, Some(Request(key, replyTo))) ⇒
replyTo ! Cached(key, None)
case _: UpdateResponse[_] ⇒ // ok
}
}
class ReplicatedCacheSpecMultiJvmNode1 extends ReplicatedCacheSpec class ReplicatedCacheSpecMultiJvmNode1 extends ReplicatedCacheSpec
class ReplicatedCacheSpecMultiJvmNode2 extends ReplicatedCacheSpec class ReplicatedCacheSpecMultiJvmNode2 extends ReplicatedCacheSpec
class ReplicatedCacheSpecMultiJvmNode3 extends ReplicatedCacheSpec class ReplicatedCacheSpecMultiJvmNode3 extends ReplicatedCacheSpec

91
akka-samples/akka-sample-distributed-data-scala/src/multi-jvm/scala/sample/distributeddata/ReplicatedMetricsSpec.scala Normal file
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package sample.distributeddata
import scala.concurrent.duration._
import akka.cluster.Cluster
import akka.cluster.ddata.DistributedData
import akka.cluster.ddata.Replicator.GetReplicaCount
import akka.cluster.ddata.Replicator.ReplicaCount
import akka.remote.testconductor.RoleName
import akka.remote.testkit.MultiNodeConfig
import akka.remote.testkit.MultiNodeSpec
import akka.testkit._
import com.typesafe.config.ConfigFactory
object ReplicatedMetricsSpec extends MultiNodeConfig {
val node1 = role("node-1")
val node2 = role("node-2")
val node3 = role("node-3")
commonConfig(ConfigFactory.parseString("""
akka.loglevel = INFO
akka.actor.provider = "akka.cluster.ClusterActorRefProvider"
akka.log-dead-letters-during-shutdown = off
"""))
}
class ReplicatedMetricsSpecMultiJvmNode1 extends ReplicatedMetricsSpec
class ReplicatedMetricsSpecMultiJvmNode2 extends ReplicatedMetricsSpec
class ReplicatedMetricsSpecMultiJvmNode3 extends ReplicatedMetricsSpec
class ReplicatedMetricsSpec extends MultiNodeSpec(ReplicatedMetricsSpec) with STMultiNodeSpec with ImplicitSender {
import ReplicatedMetricsSpec._
import ReplicatedMetrics._
override def initialParticipants = roles.size
val cluster = Cluster(system)
val replicatedMetrics = system.actorOf(ReplicatedMetrics.props(1.second, 3.seconds))
def join(from: RoleName, to: RoleName): Unit = {
runOn(from) {
cluster join node(to).address
}
enterBarrier(from.name + "-joined")
}
"Demo of a replicated metrics" must {
"join cluster" in within(10.seconds) {
join(node1, node1)
join(node2, node1)
join(node3, node1)
awaitAssert {
DistributedData(system).replicator ! GetReplicaCount
expectMsg(ReplicaCount(roles.size))
}
enterBarrier("after-1")
}
"replicate metrics" in within(10.seconds) {
val probe = TestProbe()
system.eventStream.subscribe(probe.ref, classOf[UsedHeap])
awaitAssert {
probe.expectMsgType[UsedHeap].percentPerNode.size should be(3)
}
probe.expectMsgType[UsedHeap].percentPerNode.size should be(3)
probe.expectMsgType[UsedHeap].percentPerNode.size should be(3)
enterBarrier("after-2")
}
"cleanup removed node" in within(15.seconds) {
val node3Address = node(node3).address
runOn(node1) {
cluster.leave(node3Address)
}
runOn(node1, node2) {
val probe = TestProbe()
system.eventStream.subscribe(probe.ref, classOf[UsedHeap])
awaitAssert {
probe.expectMsgType[UsedHeap].percentPerNode.size should be(2)
}
probe.expectMsgType[UsedHeap].percentPerNode should not contain (
nodeKey(node3Address))
}
enterBarrier("after-3")
}
}
}

17
akka-samples/akka-sample-distributed-data-scala/src/multi-jvm/scala/sample/distributeddata/STMultiNodeSpec.scala Normal file
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@ -0,0 +1,17 @@
package sample.distributeddata
import akka.remote.testkit.MultiNodeSpecCallbacks
import org.scalatest.{ BeforeAndAfterAll, WordSpecLike }
import org.scalatest.Matchers
/**
* Hooks up MultiNodeSpec with ScalaTest
*/
trait STMultiNodeSpec extends MultiNodeSpecCallbacks
with WordSpecLike with Matchers with BeforeAndAfterAll {
override def beforeAll() = multiNodeSpecBeforeAll()
override def afterAll() = multiNodeSpecAfterAll()
}

141
akka-samples/akka-sample-distributed-data-scala/src/multi-jvm/scala/sample/distributeddata/ServiceRegistrySpec.scala Normal file
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package sample.distributeddata
import scala.concurrent.duration._
import akka.actor.Actor
import akka.actor.PoisonPill
import akka.actor.Props
import akka.cluster.Cluster
import akka.cluster.ddata.DistributedData
import akka.cluster.ddata.Replicator.GetReplicaCount
import akka.cluster.ddata.Replicator.ReplicaCount
import akka.remote.testconductor.RoleName
import akka.remote.testkit.MultiNodeConfig
import akka.remote.testkit.MultiNodeSpec
import akka.testkit._
import com.typesafe.config.ConfigFactory
object ServiceRegistrySpec extends MultiNodeConfig {
val node1 = role("node-1")
val node2 = role("node-2")
val node3 = role("node-3")
commonConfig(ConfigFactory.parseString("""
akka.loglevel = INFO
akka.actor.provider = "akka.cluster.ClusterActorRefProvider"
akka.log-dead-letters-during-shutdown = off
"""))
class Service extends Actor {
def receive = {
case s: String ⇒ sender() ! self.path.name + ": " + s
}
}
}
class ServiceRegistrySpecMultiJvmNode1 extends ServiceRegistrySpec
class ServiceRegistrySpecMultiJvmNode2 extends ServiceRegistrySpec
class ServiceRegistrySpecMultiJvmNode3 extends ServiceRegistrySpec
class ServiceRegistrySpec extends MultiNodeSpec(ServiceRegistrySpec) with STMultiNodeSpec with ImplicitSender {
import ServiceRegistrySpec._
import ServiceRegistry._
override def initialParticipants = roles.size
val cluster = Cluster(system)
val registry = system.actorOf(ServiceRegistry.props)
def join(from: RoleName, to: RoleName): Unit = {
runOn(from) {
cluster join node(to).address
}
enterBarrier(from.name + "-joined")
}
"Demo of a replicated service registry" must {
"join cluster" in within(10.seconds) {
join(node1, node1)
join(node2, node1)
join(node3, node1)
awaitAssert {
DistributedData(system).replicator ! GetReplicaCount
expectMsg(ReplicaCount(roles.size))
}
enterBarrier("after-1")
}
"replicate service entry" in within(10.seconds) {
runOn(node1) {
val a1 = system.actorOf(Props[Service], name = "a1")
registry ! Register("a", a1)
}
awaitAssert {
val probe = TestProbe()
registry.tell(Lookup("a"), probe.ref)
probe.expectMsgType[Bindings].services.map(_.path.name) should be(Set("a1"))
}
enterBarrier("after-2")
}
"replicate updated service entry, and publish to even bus" in {
val probe = TestProbe()
system.eventStream.subscribe(probe.ref, classOf[BindingChanged])
runOn(node2) {
val a2 = system.actorOf(Props[Service], name = "a2")
registry ! Register("a", a2)
}
probe.within(10.seconds) {
probe.expectMsgType[BindingChanged].services.map(_.path.name) should be(Set("a1", "a2"))
registry.tell(Lookup("a"), probe.ref)
probe.expectMsgType[Bindings].services.map(_.path.name) should be(Set("a1", "a2"))
}
enterBarrier("after-4")
}
"remove terminated service" in {
val probe = TestProbe()
system.eventStream.subscribe(probe.ref, classOf[BindingChanged])
runOn(node2) {
registry.tell(Lookup("a"), probe.ref)
val a2 = probe.expectMsgType[Bindings].services.find(_.path.name == "a2").get
a2 ! PoisonPill
}
probe.within(10.seconds) {
probe.expectMsgType[BindingChanged].services.map(_.path.name) should be(Set("a1"))
registry.tell(Lookup("a"), probe.ref)
probe.expectMsgType[Bindings].services.map(_.path.name) should be(Set("a1"))
}
enterBarrier("after-5")
}
"replicate many service entries" in within(10.seconds) {
for (i ← 100 until 200) {
val service = system.actorOf(Props[Service], name = myself.name + "_" + i)
registry ! Register("a" + i, service)
}
awaitAssert {
val probe = TestProbe()
for (i ← 100 until 200) {
registry.tell(Lookup("a" + i), probe.ref)
probe.expectMsgType[Bindings].services.map(_.path.name) should be(roles.map(_.name + "_" + i).toSet)
}
}
enterBarrier("after-6")
}
}
}

98
akka-samples/akka-sample-distributed-data-scala/src/multi-jvm/scala/sample/distributeddata/ShoppingCartSpec.scala Normal file
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@ -0,0 +1,98 @@
package sample.distributeddata
import scala.concurrent.duration._
import akka.cluster.Cluster
import akka.cluster.ddata.DistributedData
import akka.cluster.ddata.Replicator.GetReplicaCount
import akka.cluster.ddata.Replicator.ReplicaCount
import akka.remote.testconductor.RoleName
import akka.remote.testkit.MultiNodeConfig
import akka.remote.testkit.MultiNodeSpec
import akka.testkit._
import com.typesafe.config.ConfigFactory
object ShoppingCartSpec extends MultiNodeConfig {
val node1 = role("node-1")
val node2 = role("node-2")
val node3 = role("node-3")
commonConfig(ConfigFactory.parseString("""
akka.loglevel = INFO
akka.actor.provider = "akka.cluster.ClusterActorRefProvider"
akka.log-dead-letters-during-shutdown = off
"""))
}
class ShoppingCartSpecMultiJvmNode1 extends ShoppingCartSpec
class ShoppingCartSpecMultiJvmNode2 extends ShoppingCartSpec
class ShoppingCartSpecMultiJvmNode3 extends ShoppingCartSpec
class ShoppingCartSpec extends MultiNodeSpec(ShoppingCartSpec) with STMultiNodeSpec with ImplicitSender {
import ShoppingCartSpec._
import ShoppingCart._
override def initialParticipants = roles.size
val cluster = Cluster(system)
val shoppingCart = system.actorOf(ShoppingCart.props("user-1"))
def join(from: RoleName, to: RoleName): Unit = {
runOn(from) {
cluster join node(to).address
}
enterBarrier(from.name + "-joined")
}
"Demo of a replicated shopping cart" must {
"join cluster" in within(10.seconds) {
join(node1, node1)
join(node2, node1)
join(node3, node1)
awaitAssert {
DistributedData(system).replicator ! GetReplicaCount
expectMsg(ReplicaCount(roles.size))
}
enterBarrier("after-1")
}
"handle updates directly after start" in within(15.seconds) {
runOn(node2) {
shoppingCart ! ShoppingCart.AddItem(LineItem("1", "Apples", quantity = 2))
shoppingCart ! ShoppingCart.AddItem(LineItem("2", "Oranges", quantity = 3))
}
enterBarrier("updates-done")
awaitAssert {
shoppingCart ! ShoppingCart.GetCart
val cart = expectMsgType[Cart]
cart.items should be(Set(LineItem("1", "Apples", quantity = 2), LineItem("2", "Oranges", quantity = 3)))
}
enterBarrier("after-2")
}
"handle updates from different nodes" in within(5.seconds) {
runOn(node2) {
shoppingCart ! ShoppingCart.AddItem(LineItem("1", "Apples", quantity = 5))
shoppingCart ! ShoppingCart.RemoveItem("2")
}
runOn(node3) {
shoppingCart ! ShoppingCart.AddItem(LineItem("3", "Bananas", quantity = 4))
}
enterBarrier("updates-done")
awaitAssert {
shoppingCart ! ShoppingCart.GetCart
val cart = expectMsgType[Cart]
cart.items should be(Set(LineItem("1", "Apples", quantity = 7), LineItem("3", "Bananas", quantity = 4)))
}
enterBarrier("after-3")
}
}
}

97
akka-samples/akka-sample-distributed-data-scala/src/multi-jvm/scala/sample/distributeddata/VotingServiceSpec.scala Normal file
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@ -0,0 +1,97 @@
package sample.distributeddata
import scala.concurrent.duration._
import akka.actor.Props
import akka.cluster.Cluster
import akka.cluster.ddata.DistributedData
import akka.cluster.ddata.Replicator.GetReplicaCount
import akka.cluster.ddata.Replicator.ReplicaCount
import akka.remote.testconductor.RoleName
import akka.remote.testkit.MultiNodeConfig
import akka.remote.testkit.MultiNodeSpec
import akka.testkit._
import com.typesafe.config.ConfigFactory
object VotingServiceSpec extends MultiNodeConfig {
val node1 = role("node-1")
val node2 = role("node-2")
val node3 = role("node-3")
commonConfig(ConfigFactory.parseString("""
akka.loglevel = INFO
akka.actor.provider = "akka.cluster.ClusterActorRefProvider"
akka.log-dead-letters-during-shutdown = off
"""))
}
class VotingServiceSpecMultiJvmNode1 extends VotingServiceSpec
class VotingServiceSpecMultiJvmNode2 extends VotingServiceSpec
class VotingServiceSpecMultiJvmNode3 extends VotingServiceSpec
class VotingServiceSpec extends MultiNodeSpec(VotingServiceSpec) with STMultiNodeSpec with ImplicitSender {
import VotingServiceSpec._
override def initialParticipants = roles.size
val cluster = Cluster(system)
def join(from: RoleName, to: RoleName): Unit = {
runOn(from) {
cluster join node(to).address
}
enterBarrier(from.name + "-joined")
}
"Demo of a replicated voting" must {
"join cluster" in within(10.seconds) {
join(node1, node1)
join(node2, node1)
join(node3, node1)
awaitAssert {
DistributedData(system).replicator ! GetReplicaCount
expectMsg(ReplicaCount(roles.size))
}
enterBarrier("after-1")
}
"count votes correctly" in within(15.seconds) {
import VotingService._
val votingService = system.actorOf(Props[VotingService], "votingService")
val N = 1000
runOn(node1) {
votingService ! Open
for (n ← 1 to N) {
votingService ! Vote("#" + ((n % 20) + 1))
}
}
runOn(node2, node3) {
// wait for it to open
val p = TestProbe()
awaitAssert {
votingService.tell(GetVotes, p.ref)
p.expectMsgPF(3.seconds) { case Votes(_, true) ⇒ true }
}
for (n ← 1 to N) {
votingService ! Vote("#" + ((n % 20) + 1))
}
}
enterBarrier("voting-done")
runOn(node3) {
votingService ! Close
}
val expected = (1 to 20).map(n ⇒ "#" + n -> BigInt(3L * N / 20)).toMap
awaitAssert {
votingService ! GetVotes
expectMsg(3.seconds, Votes(expected, false))
}
enterBarrier("after-2")
}
}
}

285
akka-samples/akka-sample-distributed-data-scala/tutorial/index.html Normal file
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@ -0,0 +1,285 @@
<!-- <html> -->
<head>
<title>Akka Distributed Data Samples with Scala</title>
</head>
<body>
<div>
<p>
This tutorial contains 5 samples illustrating how to use
<a href="http://doc.akka.io/docs/akka/2.4-SNAPSHOT/scala/distributed-data.html" target="_blank">Akka Distributed Data</a>.
</p>
<ul>
<li>Low Latency Voting Service</li>
<li>Highly Available Shopping Cart</li>
<li>Distributed Service Registry</li>
<li>Replicated Cache</li>
<li>Replicated Metrics</li>
</ul>
<p>
<b>Akka Distributed Data</b> is useful when you need to share data between nodes in an
Akka Cluster. The data is accessed with an actor providing a key-value store like API.
The keys are unique identifiers with type information of the data values. The values
are <i>Conflict Free Replicated Data Types</i> (CRDTs).
</p>
<p>
All data entries are spread to all nodes, or nodes with a certain role, in the cluster
via direct replication and gossip based dissemination. You have fine grained control
of the consistency level for reads and writes.
</p>
<p>
The nature CRDTs makes it possible to perform updates from any node without coordination.
Concurrent updates from different nodes will automatically be resolved by the monotonic
merge function, which all data types must provide. The state changes always converge.
Several useful data types for counters, sets, maps and registers are provided and
you can also implement your own custom data types.
</p>
<p>
It is eventually consistent and geared toward providing high read and write availability
(partition tolerance), with low latency. Note that in an eventually consistent system a read may return an
out-of-date value.
</p>
</div>
<div>
<h2>Low Latency Voting Service</h2>
<p>
Distributed Data is great for low latency services, since you can update or get data from the local replica
without immediate communication with other nodes.
</p>
<p>
Open <a href="#code/src/main/scala/sample/distributeddata/VotingService.scala" class="shortcut">VotingService.scala</a>.
</p>
<p>
<code>VotingService</code> is an actor for low latency counting of votes on several cluster nodes and aggregation
of the grand total number of votes. The actor is started on each cluster node. First it expects an
<code>Open</code> message on one or several nodes. After that the counting can begin. The open
signal is immediately replicated to all nodes with a boolean
<a href="http://doc.akka.io/docs/akka/2.4-SNAPSHOT/scala/distributed-data.html#Flags_and_Registers" target="_blank">Flag</a>.
Note <code>WriteAll</code>.
</p>
<pre><code>
replicator ! Update(OpenedKey, Flag(), WriteAll(5.seconds))(_.switchOn)
</code></pre>
<p>
The actor is subscribing to changes of the <code>OpenedKey</code> and other instances of this actor,
also on other nodes, will be notified when the flag is changed.
</p>
<pre><code>
replicator ! Subscribe(OpenedKey, self)
</code></pre>
<pre><code>
case c @ Changed(OpenedKey) if c.get(OpenedKey).enabled
</code></pre>
<p>
The counters are kept in a
<a href="http://doc.akka.io/docs/akka/2.4-SNAPSHOT/scala/distributed-data.html#Counters" target="_blank">PNCounterMap</a>
and updated with:
</p>
<pre><code>
val update = Update(CountersKey, PNCounterMap(), WriteLocal, request = Some(v)) {
_.increment(participant, 1)
}
replicator ! update
</code></pre>
<p>
Incrementing the counter is very fast, since it only involves communication with the local
<code>Replicator</code> actor. Note <code>WriteLocal</code>. Those updates are also spread
to other nodes, but that is performed in the background.
</p>
<p>
The total number of votes is retrieved with:
</p>
<pre><code>
case GetVotes ⇒
replicator ! Get(CountersKey, ReadAll(3.seconds), Some(GetVotesReq(sender())))
case g @ GetSuccess(CountersKey, Some(GetVotesReq(replyTo))) ⇒
val data = g.get(CountersKey)
replyTo ! Votes(data.entries, open)
</code></pre>
<p>
The multi-node test for the <code>VotingService</code> can be found in
<a href="#code/src/multi-jvm/scala/sample/distributeddata/VotingServiceSpec.scala" class="shortcut">VotingServiceSpec.scala</a>.
</p>
<p>
Read the
<a href="http://doc.akka.io/docs/akka/2.4-SNAPSHOT/scala/distributed-data.html#Using_the_Replicator" target="_blank">Using the Replicator</a>
documentation for more details of how to use <code>Get</code>, <code>Update</code>, and <code>Subscribe</code>.
</div>
<div>
<h2>Highly Available Shopping Cart</h2>
<p>
Distributed Data is great for highly available services, since it is possible to perform
updates to the local node (or currently available nodes) during a network partition.
</p>
<p>
Open <a href="#code/src/main/scala/sample/distributeddata/ShoppingCart.scala" class="shortcut">ShoppingCart.scala</a>.
</p>
<p>
<code>ShoppingCart</code> is an actor that holds the selected items to buy for a user.
The actor instance for a specific user may be started where ever needed in the cluster, i.e. several
instances may be started on different nodes and used at the same time.
</p>
<p>
Each product in the cart is represented by a <code>LineItem</code> and all items in the cart
is collected in a <a href="http://doc.akka.io/docs/akka/2.4-SNAPSHOT/scala/distributed-data.html#Maps" target="_blank">LWWMap</a>.
</p>
<p>
The actor handles the commands <code>GetCart</code>, <code>AddItem</code> and <code>RemoveItem</code>.
To get the latest updates in case the same shopping cart is used from several nodes it is using
consistency level of <code>ReadMajority</code> and <code>WriteMajority</code>, but that is only
done to reduce the risk of seeing old data. If such reads and writes cannot be completed due to a
network partition it falls back to reading/writing from the local replica (see <code>GetFailure</code>).
Local reads and writes will always be successful and when the network partition heals the updated
shopping carts will be be disseminated by the
<a href="https://en.wikipedia.org/wiki/Gossip_protocol" target="_blank">gossip protocol</a>
and the <code>LWWMap</code> CRDTs are merged, i.e. it is a highly available shopping cart.
</p>
<p>
The multi-node test for the <code>ShoppingCart</code> can be found in
<a href="#code/src/multi-jvm/scala/sample/distributeddata/ShoppingCartSpec.scala" class="shortcut">ShoppingCartSpec.scala</a>.
</p>
<p>
Read the
<a href="http://doc.akka.io/docs/akka/2.4-SNAPSHOT/scala/distributed-data.html#Consistency" target="_blank">Consistency</a>
section in the documentation to understand the consistency considerations.
</p>
</div>
<div>
<h2>Distributed Service Registry</h2>
<p>
Have you ever had the need to lookup actors by name in an Akka Cluster?
This example illustrates how you could implement such a registry. It is probably not
feature complete, but should be a good starting point.
</p>
<p>
Open <a href="#code/src/main/scala/sample/distributeddata/ServiceRegistry.scala" class="shortcut">ServiceRegistry.scala</a>.
</p>
<p>
<code>ServiceRegistry</code> is an actor that is started on each node in the cluster.
It supports two basic commands:
</p>
<ul>
<li><code>Register</code> to bind an <code>ActorRef</code> to a name,
several actors can be bound to the same name</li>
<li><code>Lookup</code> get currently bound services of a given name</li>
</ul>
<p>
For each named service it is using an
<a href="http://doc.akka.io/docs/akka/2.4-SNAPSHOT/scala/distributed-data.html#Sets" target="_blank">ORSet</a>.
Here we are using top level <code>ORSet</code> entries. An alternative would have been to use a
<code>ORMultiMap</code> holding all services. That would have a disadvantage if we have many services.
When a data entry is changed the full state of that entry is replicated to other nodes, i.e. when you
update a map the whole map is replicated.
</p>
<p>
The <code>ServiceRegistry</code> is subscribing to changes of a <code>GSet</code> where we add
the names of all services. It is also subscribing to all such service keys to get notifications when
actors are added or removed to a named service.
</p>
<p>
The multi-node test for the <code>ServiceRegistry</code> can be found in
<a href="#code/src/multi-jvm/scala/sample/distributeddata/ServiceRegistrySpec.scala" class="shortcut">ServiceRegistrySpec.scala</a>.
</p>
</div>
<div>
<h2>Replicated Cache</h2>
<p>
This example illustrates a simple key-value cache.
</p>
<p>
Open <a href="#code/src/main/scala/sample/distributeddata/ReplicatedCache.scala" class="shortcut">ReplicatedCache.scala</a>.
</p>
<p>
<code>ReplicatedCache</code> is an actor that is started on each node in the cluster.
It supports three commands: <code>PutInCache</code>, <code>GetFromCache</code> and <code>Evict</code>.
</p>
<p>
It is splitting up the key space in 100 top level keys, each with a <code>LWWMap</code>.
When a data entry is changed the full state of that entry is replicated to other nodes, i.e. when you
update a map the whole map is replicated. Therefore, instead of using one ORMap with 1000 elements it
is more efficient to split that up in 100 top level ORMap entries with 10 elements each. Top level
entries are replicated individually, which has the trade-off that different entries may not be
replicated at the same time and you may see inconsistencies between related entries.
Separate top level entries cannot be updated atomically together.
</p>
<p>
The multi-node test for the <code>ReplicatedCache</code> can be found in
<a href="#code/src/multi-jvm/scala/sample/distributeddata/ReplicatedCacheSpec.scala" class="shortcut">ReplicatedCacheSpec.scala</a>.
</p>
</div>
<div>
<h2>Replicated Metrics</h2>
<p>
This example illustrates to spread metrics data to all nodes in an Akka cluster.
</p>
<p>
Open <a href="#code/src/main/scala/sample/distributeddata/ReplicatedMetrics.scala" class="shortcut">ReplicatedMetrics.scala</a>.
</p>
<p>
<code>ReplicatedMetrics</code> is an actor that is started on each node in the cluster.
Periodically it collects some metrics, in this case used and max heap size.
Each metrics type is stored in a <code>LWWMap</code> where the key in the map is the address of
the node. The values are disseminated to other nodes with the gossip protocol.
</p>
<p>
The multi-node test for the <code>ReplicatedCache</code> can be found in
<a href="#code/src/multi-jvm/scala/sample/distributeddata/ReplicatedMetricsSpec.scala" class="shortcut">ReplicatedMetricsSpec.scala</a>.
</p>
</div>
</body>
</html>

5
project/AkkaBuild.scala
View file

@ -210,7 +210,8 @@ object AkkaBuild extends Build {
Seq(sampleCamelJava, sampleCamelScala, sampleClusterJava, sampleClusterScala, sampleFsmScala, sampleFsmJavaLambda, Seq(sampleCamelJava, sampleCamelScala, sampleClusterJava, sampleClusterScala, sampleFsmScala, sampleFsmJavaLambda,
sampleMainJava, sampleMainScala, sampleMainJavaLambda, sampleMultiNodeScala, sampleMainJava, sampleMainScala, sampleMainJavaLambda, sampleMultiNodeScala,
samplePersistenceJava, samplePersistenceScala, samplePersistenceJavaLambda, samplePersistenceJava, samplePersistenceScala, samplePersistenceJavaLambda,
sampleRemoteJava, sampleRemoteScala, sampleSupervisionJavaLambda) sampleRemoteJava, sampleRemoteScala, sampleSupervisionJavaLambda,
sampleDistributedDataScala)
) )
lazy val sampleCamelJava = Sample.project("akka-sample-camel-java") lazy val sampleCamelJava = Sample.project("akka-sample-camel-java")
@ -236,6 +237,8 @@ object AkkaBuild extends Build {
lazy val sampleRemoteScala = Sample.project("akka-sample-remote-scala") lazy val sampleRemoteScala = Sample.project("akka-sample-remote-scala")
lazy val sampleSupervisionJavaLambda = Sample.project("akka-sample-supervision-java-lambda") lazy val sampleSupervisionJavaLambda = Sample.project("akka-sample-supervision-java-lambda")
lazy val sampleDistributedDataScala = Sample.project("akka-sample-distributed-data-scala")
lazy val osgiDiningHakkersSampleMavenTest = Project(id = "akka-sample-osgi-dining-hakkers-maven-test", lazy val osgiDiningHakkersSampleMavenTest = Project(id = "akka-sample-osgi-dining-hakkers-maven-test",
base = file("akka-samples/akka-sample-osgi-dining-hakkers-maven-test"), base = file("akka-samples/akka-sample-osgi-dining-hakkers-maven-test"),