Scala+Akka Typed应用无日志输出问题排查求助

问题描述 #

开发了由UserActor、Main、RoomActor组成的聊天应用，运行后无任何日志输出。已尝试添加Thread.sleep(5000)、调整logback.xml将root级别设为DEBUG/INFO、用Await.result(system.whenTerminated, Duration.Inf)替换Thread.sleep，问题依旧。

核心错误点与修复方案 #

1. Main类的ActorSystem初始化错误 #

错误原因：

• 错误创建了空行为的ActorSystem（ActorSystem(Behaviors.empty, "ChatSystem")），该系统无法驱动Actor生命周期、处理消息。
• 使用system.systemActorOf创建子Actor不符合Typed Actor规范，且提前调用system.terminate()导致Actor未处理消息就被终止。
• Main的Behavior定义后未被执行，代码流程直接走到终止逻辑。

修复后的Main代码：

package Chat

import akka.actor.typed.{ActorRef, ActorSystem, Behavior}
import akka.actor.typed.scaladsl.Behaviors
import scala.concurrent.Await
import scala.concurrent.duration.Duration

object Main extends App {
    sealed trait MainCommand

    def apply(): Behavior[MainCommand] = Behaviors.setup { context =>
        // 用context.spawn正确创建子Actor
        val userActor = context.spawn(UserActor(), "userActor")
        val roomActor = context.spawn(RoomActor(), "roomActor")

        // 传递正确的userActor引用，替代deadLetters
        userActor ! UserActor.CreateUser("John", "Doe", 25, userActor)
        val roomName = "General"
        roomActor ! RoomActor.CreateRoom(userActor, roomName)

        userActor ! UserActor.SendMessageToRoom(roomActor, "Hello, everyone!", "John")

        Behaviors.receiveMessage {
            case _ =>
                context.log.info("Unknown message for MainActor")
                Behaviors.same
        }
    }

    // 启动Main作为ActorSystem的根行为，等待系统终止
    val system = ActorSystem(Main(), "ChatSystem")
    Await.result(system.whenTerminated, Duration.Inf)
}

2. UserActor的状态更新失效 #

错误原因：
CreateUser分支中，创建新用户后仅生成了新的用户Map，但未返回携带新状态的userBehavior，导致用户状态无法持久化。后续SendMessageToRoom会因找不到用户抛出异常，Actor重启后日志被吞。

修复后的UserActor关键分支：

case CreateUser(name, surname, age, userActor) =>
    val userId = UUID.randomUUID().toString
    val newUser = User(name, surname, age, userId, userActor)
    context.log.info(s"User $newUser added in user list")
    context.log.info(s"Created user: $userId")
    // 返回携带新状态的Behavior，更新用户列表
    userBehavior(users + (userId -> newUser))

3. UserActor中CreateUser的参数错误 #

错误原因：
发送CreateUser时传递的userActor是system.deadLetters，导致后续用户消息被发送到死信邮箱，无法触发日志输出。

修复：
在Main中发送消息时，将参数替换为实际的userActor引用：

userActor ! UserActor.CreateUser("John", "Doe", 25, userActor)

4. RoomActor的LeaveRoom逻辑错误 #

错误原因：

• 使用rooms.get(roomName).foreach处理房间时，内部返回的roomBehavior会被忽略，导致房间状态无法更新。
• 分支末尾重复输出日志，逻辑混乱导致状态不一致。

修复后的RoomActor LeaveRoom分支：

case LeaveRoom(user, roomName) =>
    rooms.get(roomName) match {
        case Some(room) =>
            room.users -= user
            if(user == room.owner) {
                if(room.users.isEmpty) {
                    context.log.info(s"$user was the owner and the last user in room: $roomName. Removing the room.")
                    roomBehavior(rooms - roomName)
                } else {
                    val newOwner = room.users.head
                    context.log.info(s"$user was the owner. Assigning the new owner: $newOwner")
                    val updatedRoom = room.copy(owner = newOwner)
                    roomBehavior(rooms + (roomName -> updatedRoom))
                }
            } else {
                context.log.info(s"$user left the room: $roomName")
                room.users.foreach { elem =>
                    elem ! UserActor.LeftRoomNotification(user, roomName)
                }
                roomBehavior(rooms + (roomName -> room))
            }
        case None =>
            context.log.warn(s"Room $roomName does not exist")
            Behaviors.same
    }

补充配置说明 #

确保logback.xml放在src/main/resources下，示例配置：

<configuration>
    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
        </encoder>
    </appender>
    <root level="INFO">
        <appender-ref ref="STDOUT" />
    </root>
</configuration>

内容的提问来源于stack exchange，提问作者Ch1rae