Google Pub/Sub 订阅者没有收到消息

Question

首先，我没有使用 Akka 的经验，所以我自己调试起来真的很糟糕。我尝试了 here 中的示例，发布消息有效（这意味着凭据有效），但没有发出任何消息。服务帐户被授予所有权限。

我的代码是这样的，基本上和例子中的一模一样：

package com.example.google.pubsub

import java.io.FileInputStream
import java.security.spec.PKCS8EncodedKeySpec
import java.security.{KeyFactory, PrivateKey}
import java.util.Base64

import akka.actor.ActorSystem
import akka.stream.{ActorMaterializer, Attributes, Outlet, SourceShape}
import akka.stream.alpakka.googlecloud.pubsub.scaladsl.GooglePubSub
import akka.stream.alpakka.googlecloud.pubsub._
import akka.stream.scaladsl.{Sink, Source}
import akka.stream.stage.{GraphStage, GraphStageLogic}
import akka.{Done, NotUsed}
import com.google.api.client.googleapis.auth.oauth2.GoogleCredential

import scala.concurrent.duration._
import scala.concurrent.Future

object SubscriberMain extends App {
  println("#### SUBSCRIBER ####")

  val privateKey: PrivateKey = {
    import java.io.FileInputStream
    val credential = GoogleCredential.fromStream(new FileInputStream("mycredentials.json"))
    val privateKey = credential.getServiceAccountPrivateKey
    privateKey
  }
  val clientEmail = "main-19@weirdproject.iam.gserviceaccount.com"
  val projectId = "weirdproject"
  val apiKey = "xxxx"
  val subscription = "somesubscription"

  implicit val system = ActorSystem()
  implicit val mat = ActorMaterializer()

  val subscriptionSource: Source[ReceivedMessage, NotUsed] =
    GooglePubSub.subscribe(projectId, apiKey, clientEmail, privateKey, subscription)

  val ackSink: Sink[AcknowledgeRequest, Future[Done]] =
    GooglePubSub.acknowledge(projectId, apiKey, clientEmail, privateKey, subscription)

  subscriptionSource
    .map { message =>
      val data = message.message.data
      println(s"received a message: $data")
      message.ackId
    }
    .groupedWithin(1000, 1.minute)
    .map(AcknowledgeRequest.apply)
    .to(ackSink)

}

我发现akka.stream.alpakka.googlecloud.pubsub.GooglePubSubSource.createLogic从来没有被执行过，这似乎是没有获取消息的原因。

Answer 1

您拥有的是流的定义，但您不是运行它。调用 run():

subscriptionSource
  .map { message =>
    val data = message.message.data
    println(s"received a message: $data")
    message.ackId
  }
  .groupedWithin(1000, 1.minute)
  .map(AcknowledgeRequest.apply)
  .to(ackSink)
  .run() // <---

或者，使用 runWith()，这是一种方便的方法 returns Sink 的物化值：

val result: Future[Done] =
  subscriptionSource
    .map { message =>
      val data = message.message.data
      println(s"received a message: $data")
      message.ackId
    }
    .groupedWithin(1000, 1.minute)
    .map(AcknowledgeRequest.apply)
    .runWith(ackSink)

找到更多关于定义和运行流的信息 here。

Google Pub/Sub 订阅者没有收到消息

Google Pub/Sub Subscriber does not receive messages

scala

google-cloud-platform

akka

akka-stream

alpakka