playframework - 如何使用 Akka 配置 play 应用程序在集群中运行

Question

我有一个要在集群中运行的 PlayFramework (play-scala) 应用程序。所以我可能有几个运行此应用程序镜像的 docker 容器。我提前不知道这些的IP地址，因为云服务提供商可以动态启动和停止它们，所以我无法指定种子节点。此外，对于应用程序的每个实例，所有 application.conf 文件都应该相同吗？

如何配置 play 应用程序以使应用程序的每个实例都能发现并加入 Akka 集群？

我看过: https://www.playframework.com/documentation/2.7.x/ScalaAkka#Akka-Cluster Akka cluster setup with play framework https://github.com/lregnier/play-akka-cluster-aws

我必须使用 Akka Cluster Bootstrap 吗？因为我不能指定种子节点？

在 application.conf 文件中包含以下内容是否足够(取自 Cluster Usage :

akka {
  actor {
    provider = "cluster"
  }
  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 downing is NOT safe for production deployments.
    # you may want to use it during development, read more about it in the docs.
    #
    # auto-down-unreachable-after = 10s
  }
}

但是没有种子节点？如果是这样，节点如何发现并加入集群？

Answer 1

鉴于要求，最好的选择可能是使用 Akka Cluster Bootstrap .要运行基于容器的服务，service discovery使用 AWS ECS 或 Kubernetes 可能更接近您的需求。

Akka Cluster Bootstrap通过自动集群引导机制解决您对没有预先分配的种子节点的需求。每个节点通过其公开的 HTTP 端点相互探测，如果没有 seed nodes存在(即不存在集群)，具有“最低”地址的节点将使自己成为 seed node提示其他节点加入新形成的集群。有关详细信息，请参阅此 Akka doc re: cluster bootstrap .

如 Akka 文档中所述，Akka Cluster Bootstrap取决于模块 Akka Discovery和 Akka Management :

libraryDependencies ++= Seq(
  "com.lightbend.akka.management" %% "akka-management-cluster-bootstrap" % "1.0.1",
  "com.typesafe.akka" %% "akka-discovery" % "2.5.21"
)

对于 service discovery using ECS , 分配 aws-api-ecs或 aws-api-ecs-async (对于非阻塞 IO)到 akka.discovery.method在application.conf这可能看起来像下面这样:

akka {
  cluster {
    seed-nodes = []
    seed-nodes = ${?SEED_NODES}
  }
  # ...
  management {
    cluster.bootstrap {
      contact-point-discovery {
        required-contact-point-nr = 2
        required-contact-point-nr = ${?REQUIRED_CONTACT_POINTS}
      }
    }
    # ...
  }
  discovery {
    method = aws-api-ecs-async
    aws-api-ecs-async {
      cluster = "my-ecs-cluster"
    }
  }
}

对于 service discovery using Kubernetes , akka.discovery.method应该分配 kubernetes-api在application.conf可能如下所示:

akka {
  cluster {
    seed-nodes = []
    seed-nodes = ${?SEED_NODES}
  }
  # ...
  management {
    cluster.bootstrap {
      contact-point-discovery {
        required-contact-point-nr = 2
        required-contact-point-nr = ${?REQUIRED_CONTACT_POINTS}
      }
    }
    # ...
  }
  discovery {
    method = kubernetes-api
    kubernetes-api {
      pod-namespace = "default"
      pod-namespace = ${?K8S_NAMESPACE}
      pod-label-selector = "app=akka-cluster"
      pod-label-selector = ${?K8S_SELECTOR}
      pod-port-name = "cluster-mgmt-port"
      pod-port-name = ${?K8S_MANAGEMENT_PORT}
    }
  }
}