# Scala+Akka 実践ティップス
**URL:** https://forum.ficusonline.com/t/topic/394
**Category:** Programming
**Created:** [2020 年 11 月 12 日午前 9:03 UTC](https://forum.ficusonline.com/t/topic/394 "2020-11-12T09:03:33Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@tk-fuse](https://forum.ficusonline.com/u/tk-fuse)
#### Post date: [2020 年 11 月 12 日午前 9:03 UTC](https://forum.ficusonline.com/t/topic/394/1 "2020-11-12T09:03:33Z")
## 実践的なコードによるScalaティップス
当初、 **Scala** の導入目的は、オープンソースアプリのバグ修正・コード改訂でしたが、アクターモデルによるアルゴリズムがデータマネージメントアプリを作成するのに有用だと考え、より深く学習することにしました。導入時のややっこしい内容を、実際のコードで理解するためのティップスをここに纏めます。サンプルコード内でのActorは、旧版（Classic）のAPIにより記述されていることが多いため、時間があれば新APIに変換してみて下さい。新旧API混在での記述もサポートしています。
## パターンマッチング
[https://dzone.com/articles/8-scala-pattern-matching-tricks](https://dzone.com/articles/8-scala-pattern-matching-tricks)
### Name Binding
```auto
def requestMoreInfo(p: Person): String = { ... }
val bob = Person("Bob", 34, List("Inception", "The Departed"))
val bobsInfo = bob match {
case Person(name, age, movies) => s"$name's info: ${requestMoreInfo(Person(name, age, movies))}"
}
```
**“p @”** による代替
```auto
val bobsInfo = bob match {
case p @ Person(name, _, _) => s"$name's info: ${requestMoreInfo(p)}"
}
```
**“movies @”** による代替
```auto
val bobsInception = bob match {
case Person(name, _, movies @ List("Inception", _*)) => s"$name REALLY likes Inception, some other movies too: $movies"
}
```
---
### Author:  [@tk-fuse](https://forum.ficusonline.com/u/tk-fuse)
#### Post date: [2020 年 11 月 30 日午前 9:43 UTC](https://forum.ficusonline.com/t/topic/394/2 "2020-11-30T09:43:33Z")
## Akkaアクターシステムの設定とSLF4Jによるアクターのログ取得
> **[Logging • Akka core](https://doc.akka.io/libraries/akka-core/current/typed/logging.html)**
>
> Logging options with Akka.
アクター間のメッセージの遣り取りを、SLF4Jによるログシステムにより確認します。スケジューラーにより5秒毎にメッセージの遣り取りが実行されます。
> **[akka-in-action/chapter-conf-deploy at master · capitalfuse/akka-in-action](https://github.com/capitalfuse/akka-in-action/tree/master/chapter-conf-deploy)**
>
> Accompanying source code for akka in action . Contribute to capitalfuse/akka-in-action development by creating an account on GitHub.
**build.sbt**
```auto
name := "deploy"
version := "1.0"
organization := "manning"
scalacOptions ++= Seq(
"-deprecation",
"-unchecked",
"-Xlint",
"-Ywarn-unused",
"-Ywarn-dead-code",
"-feature",
"-language:_"
)
enablePlugins(JavaAppPackaging)
scriptClasspath +="../conf"
libraryDependencies ++= {
val akkaVersion = "2.6.10"
Seq(
"com.typesafe.akka" %% "akka-actor" % akkaVersion,
"com.typesafe.akka" %% "akka-slf4j" % akkaVersion,
"ch.qos.logback" % "logback-classic" % "1.2.3",
"com.typesafe.akka" %% "akka-testkit" % akkaVersion % "test",
"org.scalatest" %% "scalatest" % "3.2.2" % "test"
)
}
```
**scala.sbt**
```auto
scalaVersion := "2.13.1"
scalacOptions ++= Seq(
"-deprecation",
"-unchecked",
"-Xfatal-warnings",
"-feature",
"-language:_"
)
```
**appilication.conf**
> **[Akka 2.10.17 - akka.event.slf4j.Slf4jLogger](https://doc.akka.io/api/akka-core/current//akka/event/slf4j/Slf4jLogger.html)**
>
> Akka 2.10.17 - akka.event.slf4j.Slf4jLogger
```auto
akka {
loggers = ["akka.event.slf4j.Slf4jLogger"]
# Options: ERROR, WARNING, INFO, DEBUG
loglevel = "DEBUG"
}
```
**reference.conf**
```auto
helloWorld {
timer=5000
}
```
**BootHello.scala**
```auto
package aia.deploy
import akka.actor.{ Props, ActorSystem }
import scala.concurrent.duration._
object BootHello extends App {
val system = ActorSystem("hello-kernel")
val actor = system.actorOf(Props[HelloWorld])
val config = system.settings.config
val timer = config.getInt("helloWorld.timer")
system.actorOf(Props(
new HelloWorldCaller(
timer = timer millis,
actor = actor)))
}
```
**HelloWorld.scala**
```auto
package aia.deploy
import akka.actor.{Actor, ActorLogging, ActorRef}
import scala.concurrent.ExecutionContextExecutor
import scala.concurrent.duration._
class HelloWorld extends Actor
with ActorLogging {
def receive: Receive = {
case msg: String =>
val hello = "Hello %s".format(msg)
sender() ! hello
log.info("Sent response {}",hello)
}
}
class HelloWorldCaller(timer: FiniteDuration, actor: ActorRef)
extends Actor with ActorLogging {
case class TimerTick(msg: String)
override def preStart(): Unit = {
super.preStart()
implicit val ec: ExecutionContextExecutor = context.dispatcher
context.system.scheduler.scheduleAtFixedRate(
timer,
timer,
self,
TimerTick("everybody"))
}
def receive: Receive = {
case msg: String => log.info("received {}",msg)
case tick: TimerTick => actor ! tick.msg
}
}
```
**実行結果**
```auto
[INFO] [11/30/2020 17:47:30.471] [hello-kernel-akka.actor.default-dispatcher-6] [akka://hello-kernel/user/$a] Sent response Hello everybody
[INFO] [11/30/2020 17:47:30.471] [hello-kernel-akka.actor.default-dispatcher-7] [akka://hello-kernel/user/$b] received Hello everybody
[INFO] [11/30/2020 17:47:35.439] [hello-kernel-akka.actor.default-dispatcher-5] [akka://hello-kernel/user/$a] Sent response Hello everybody
[INFO] [11/30/2020 17:47:35.439] [hello-kernel-akka.actor.default-dispatcher-7] [akka://hello-kernel/user/$b] received Hello everybody
[INFO] [11/30/2020 17:47:40.439] [hello-kernel-akka.actor.default-dispatcher-5] [akka://hello-kernel/user/$a] Sent response Hello everybody
[INFO] [11/30/2020 17:47:40.439] [hello-kernel-akka.actor.default-dispatcher-7] [akka://hello-kernel/user/$b] received Hello everybody
[INFO] [11/30/2020 17:47:45.438] [hello-kernel-akka.actor.default-dispatcher-7] [akka://hello-kernel/user/$a] Sent response Hello everybody
[INFO] [11/30/2020 17:47:45.438] [hello-kernel-akka.actor.default-dispatcher-5] [akka://hello-kernel/user/$b] received Hello everybody
........................
........................
```
---
### Author:  [@tk-fuse](https://forum.ficusonline.com/u/tk-fuse)
#### Post date: [2020 年 12 月 3 日午前 5:23 UTC](https://forum.ficusonline.com/t/topic/394/3 "2020-12-03T05:23:13Z")
### REST API サンプルコード
> **[Chapter 2. Up and running · Akka in Action](https://livebook.manning.com/book/akka-in-action/chapter-2/33)**
>
> Fetching a project template · Building a minimal Akka app for the cloud · Deploying to Heroku
**イベントとそのチケット数の登録・チケット購入システム**
> **[akka-in-action/chapter-up-and-running at master · capitalfuse/akka-in-action](https://github.com/capitalfuse/akka-in-action/tree/master/chapter-up-and-running)**
>
> Accompanying source code for akka in action . Contribute to capitalfuse/akka-in-action development by creating an account on GitHub.
プロジェクトフォルダでサーバ起動
```auto
$ sbt run
INFO [Slf4jLogger]: Slf4jLogger started
Success
INFO [go-ticks]: RestApi bound to /0:0:0:0:0:0:0:0:5000
```
イベントRHCPのチケットを10枚ポスト
```auto
$ http POST localhost:5000/events/RHCP tickets:=10
HTTP/1.1 201 Created
Content-Length: 28
Content-Type: application/json
Date: Thu, 03 Dec 2020 04:45:27 GMT
Server: GoTicks.com REST API
{
"name": "RHCP",
"tickets": 10
}
```
イベントDjMadlibのチケットを15枚ポスト
```auto
$ http POST localhost:5000/events/DjMadlib tickets:=15
HTTP/1.1 201 Created
Content-Length: 32
Content-Type: application/json
Date: Thu, 03 Dec 2020 04:45:51 GMT
Server: GoTicks.com REST API
{
"name": "DjMadlib",
"tickets": 15
}
```
イベント詳細確認
```auto
$ http GET localhost:5000/events
HTTP/1.1 200 OK
Content-Length: 74
Content-Type: application/json
Date: Thu, 03 Dec 2020 04:46:42 GMT
Server: GoTicks.com REST API
{
"events": [
{
"name": "DjMadlib",
"tickets": 15
},
{
"name": "RHCP",
"tickets": 10
}
]
}
```
イベントRHCPのチケットを2枚購入
```auto
$ http POST localhost:5000/events/RHCP/tickets tickets:=2
HTTP/1.1 201 Created
Content-Length: 46
Content-Type: application/json
Date: Thu, 03 Dec 2020 04:46:59 GMT
Server: GoTicks.com REST API
{
"entries": [
{
"id": 1
},
{
"id": 2
}
],
"event": "RHCP"
}
```
イベント詳細確認（RHCPのチケット数確認）
```auto
$ http GET localhost:5000/events
HTTP/1.1 200 OK
Content-Length: 73
Content-Type: application/json
Date: Thu, 03 Dec 2020 04:47:35 GMT
Server: GoTicks.com REST API
{
"events": [
{
"name": "DjMadlib",
"tickets": 15
},
{
"name": "RHCP",
"tickets": 8
}
]
}
```
---
### Author:  [@tk-fuse](https://forum.ficusonline.com/u/tk-fuse)
#### Post date: [2020 年 12 月 4 日午前 6:21 UTC](https://forum.ficusonline.com/t/topic/394/4 "2020-12-04T06:21:26Z")
### “onComplete” to handle success and failure
**Scalaシェル(REPL)**
```auto
scala> :paste
// Entering paste mode (ctrl-D to finish)
import scala.util._ // Imports statement for Try, Success, and Failure
import scala.concurrent._
import ExecutionContext.Implicits.global
val futureFail = Future { throw new Exception("error!")}
futureFail.onComplete {
case Success(value) => println(value)
case Failure(e) => println(e)
}
// Exiting paste mode, now interpreting.
```
**Exceptionによるエラー警告表示**
```auto
java.lang.Exception: error!
```
---
### Author:  [@tk-fuse](https://forum.ficusonline.com/u/tk-fuse)
#### Post date: [2020 年 12 月 7 日午前 8:57 UTC](https://forum.ficusonline.com/t/topic/394/5 "2020-12-07T08:57:43Z")
### REST APIサンプルコードの分割処理
> **[Chapter 6. Your first distributed Akka app · Akka in Action](https://livebook.manning.com/book/akka-in-action/chapter-6/17)**
>
> Introducing scaling out · Distributing the GoTicks.com app · Distributing actors with the remote module · Testing distributed actor systems
負荷分散・拡張性を目的とした **リモートノード** を **バックエンド** として配置
> **[akka-in-action/chapter-remoting at master · capitalfuse/akka-in-action](https://github.com/capitalfuse/akka-in-action/tree/master/chapter-remoting)**
>
> Accompanying source code for akka in action . Contribute to capitalfuse/akka-in-action development by creating an account on GitHub.
シングルノードによる処理からノード分割による処理
**IntelliJ** の **sbtシェル** か **Runメニュ** ーから
**FrontendRemoteDeployMain**
を実行
```auto
[IJ]sbt:goticks> run
[warn] Multiple main classes detected. Run 'show discoveredMainClasses' to see the list
Multiple main classes detected, select one to run:
[1] com.goticks.BackendMain
[2] com.goticks.BackendRemoteDeployMain
[3] com.goticks.FrontendMain
[4] com.goticks.FrontendRemoteDeployMain
[5] com.goticks.FrontendRemoteDeployWatchMain
[6] com.goticks.SingleNodeMain
Enter number: 4
[info] running com.goticks.FrontendRemoteDeployMain
[DEBUG] [12/07/2020 23:26:00.983] [run-main-0] [EventStream] StandardOutLogger started
INFO [Slf4jLogger]: Slf4jLogger started
[DEBUG] [12/07/2020 23:26:01.872] [run-main-0] [EventStream(akka://frontend)] logger log1-Slf4jLogger started
[DEBUG] [12/07/2020 23:26:01.874] [run-main-0] [EventStream(akka://frontend)] Default Loggers started
WARN [RemoteActorRefProvider]: Using the 'remote' ActorRefProvider directly, which is a low-level layer. For most use cases, the 'cluster' abstraction on top of remoting is more suitable instead.
WARN [RemoteActorRefProvider]: Akka Cluster not in use - Using Akka Cluster is recommended if you need remote watch and deploy.
INFO [ArteryTcpTransport]: Remoting started with transport [Artery tcp]; listening on address [akka://frontend@127.0.1.1:25520] with UID [8779393747958428879]
Success
INFO [go-ticks]: RestApi bound to /0:0:0:0:0:0:0:0:5000
```
フロントエンドとバックエンドが起動するので、同じくIntelliJのターミナルからhttpユーティリティにより、イベントとそのチケット数の **POST** や、 **GET** にてイベントの確認などをして下さい。
```auto
$ http POST localhost:5000/events/RHCP tickets:=10
HTTP/1.1 201 Created
Content-Length: 28
Content-Type: application/json
Date: Mon, 07 Dec 2020 14:32:23 GMT
Server: GoTicks.com REST API
{
"name": "RHCP",
"tickets": 10
}
```
```auto
$ http GET localhost:5000/events/RHCP
HTTP/1.1 200 OK
Content-Length: 28
Content-Type: application/json
Date: Mon, 07 Dec 2020 14:33:38 GMT
Server: GoTicks.com REST API
{
"name": "RHCP",
"tickets": 10
}
```
---
### Author:  [@tk-fuse](https://forum.ficusonline.com/u/tk-fuse)
#### Post date: [2020 年 12 月 8 日午前 5:27 UTC](https://forum.ficusonline.com/t/topic/394/6 "2020-12-08T05:27:59Z")
### Akkaクラスター
**Multi JVM Testing**
> **[Multi JVM Testing • Akka core](https://doc.akka.io/libraries/akka-core/current/multi-jvm-testing.html)**
>
> Multi JVM testing of distributed systems built with Akka.
**Multi Node Testing**
> **[Multi Node Testing • Akka core](https://doc.akka.io/libraries/akka-core/current/multi-node-testing.html)**
>
> Multi node testing of distributed systems built with Akka.
**Akkaクラスタードキュメント**
> **[Cluster Usage • Akka core](https://doc.akka.io/libraries/akka-core/current/typed/cluster.html)**
>
> Build distributed applications that scale across the network with Akka Cluster, a fault-tolerant decentralized peer-to-peer based cluster node membership service with no single point of failure.
> **[Chapter 14. Clustering · Akka in Action](https://livebook.manning.com/book/akka-in-action/chapter-14/)**
>
> Dynamically scaling actors in a cluster · Sending messages into the cluster with cluster-aware routers · Building a clustered Akka app
**サンプルコード開発環境変更**
- Java SDK 11.0.9
- Scala:2.13.4
- Akka:2.6.10
- sbt:1.3.13
旧リモート設定(TCP)は非推奨のため、 **Artery** リモート設定(UDP)へ変更
**Classic Remoting**
> **[Remoting • Akka core](https://doc.akka.io/libraries/akka-core/current/remoting-artery.html)**
>
> Details about the underlying remoting module for Akka Cluster.
**Artery Remoting**
> **[Remoting • Akka core](https://doc.akka.io/libraries/akka-core/current/remoting-artery.html)**
>
> Details about the underlying remoting module for Akka Cluster.
**移行ガイド**
> **[Migration Guide 2.5.x to 2.6.x • Akka core](https://doc.akka.io/libraries/akka-core/current/project/migration-guide-2.5.x-2.6.x.html)**
>
> Migrating to Akka 2.6.
**Split Brain Resolver**
> **[Split Brain Resolver • Akka core](https://doc.akka.io/libraries/akka-core/current/split-brain-resolver.html)**
>
> Akka is a toolkit for building highly concurrent, distributed, and resilient message-driven applications for Java and Scala.
**Downing**
> **[Cluster Usage • Akka core](https://doc.akka.io/libraries/akka-core/current/typed/cluster.html)**
>
> Build distributed applications that scale across the network with Akka Cluster, a fault-tolerant decentralized peer-to-peer based cluster node membership service with no single point of failure.
**Akkaクラスターサンプルコード**
> **[akka-in-action/chapter-cluster at master · capitalfuse/akka-in-action](https://github.com/capitalfuse/akka-in-action/tree/master/chapter-cluster)**
>
> Accompanying source code for akka in action . Contribute to capitalfuse/akka-in-action development by creating an account on GitHub.
メッセージとして以下の **List** を送信し、 **Worker** が各単語の合計数をカウントする。
`List("this is a test ", "this is a test", "this is", "this")`
タスクフロー
**変更箇所**
最新のSDKで動作確認できるようコード修正、ファイル追加など
>
**実行** （test2は1回のみカウント、test3はListを重複させ100回カウント、test4は”FAIL”検出によるエラー処理テスト）
```auto
$ sbt test
[info] welcome to sbt 1.3.13 (AdoptOpenJDK Java 11.0.9.1)
[info] loading global plugins from /home/user/.sbt/1.0/plugins
[info] loading settings for project chapter-cluster-build from plugins.sbt ...
[info] loading project definition from /home/user/IdeaProjects/akka-in-action/chapter-cluster/project
[info] loading settings for project chapter-cluster from scala.sbt,build.sbt ...
[info] set current project to words-cluster (in build file:/home/user/IdeaProjects/akka-in-action/chapter-cluster/)
INFO [Slf4jLogger]: Slf4jLogger started
INFO [TestReceptionist]: Received job test2
...
...
INFO [TestReceptionist]: Job test2 complete.
INFO [TestReceptionist]: result:Map(this -> 4, is -> 3, a -> 2, test -> 2)
...
...
INFO [TestReceptionist]: Job test3 complete.
INFO [TestReceptionist]: result:Map(this -> 800, is -> 600, a -> 400, test -> 400)
INFO [TestReceptionist]: Received job test4
...
ERROR [TestReceptionist]: Job Master Actor[akka://test/user/receptionist/master-test4#-490024209] terminated before finishing job.
ERROR [TestReceptionist]: Job test4 failed.
...
INFO [TestReceptionist]: Job test4 complete.
INFO [TestReceptionist]: result:Map(this -> 1, is -> 1, a -> 1, test -> 1)
...
[info] LocalWordsSpec:
[info] The words system
[info] - must count the occurrence of words in a text
[info] - must count many occurences of words in a text
[info] - must continue to process a job with intermittent failures
[info] Run completed in 3 seconds, 285 milliseconds.
[info] Total number of tests run: 3
[info] Suites: completed 1, aborted 0
[info] Tests: succeeded 3, failed 0, canceled 0, ignored 0, pending 0
[info] All tests passed.
[success] Total time: 8 s, completed Dec 12, 2020, 10:30:53 PM
```
設定ファイルによる各ノード（シードノード、マスターノード、ワーカーノード）の動作確認
**sbt-assembly** により **jar** ファイル作成( **target/words-node.jar** )
```auto
$ sbt assemply
```
ポートと設定ファイルを指定してノード起動（別ターミナルで起動すること）
> $ java -DPORT=2551 -Dconfig.resource=/seed.conf -jar target/words-node.jar
> $ java -DPORT=2554 -Dconfig.resource=/master.conf -jar target/words-node.jar
> $ java -DPORT=2555 -Dconfig.resource=/worker.conf -jar target/words-node.jar
> $ java -DPORT=2556 -Dconfig.resource=/worker.conf -jar target/words-node.jar