如何配置Nomad组内任务为不同实例分配不同存储卷？

元数据 #

• Nomad v1.7.2
• 操作系统：Windows
• 调度器：service
• 驱动：exec / raw_exec

架构说明 #

我有10台运行Nomad客户端节点的Windows服务器。

我希望通过Nomad运行3个有状态服务实例。每个实例（01、02、03）会将检查点和数据写入文件系统（例如/tmp/instance01、/tmp/instance02、/tmp/instance03）。实例重启时会从最新检查点恢复运行。每个实例可分配至任意主机，但重启后需使用与之前故障实例相同的目录。

即：

• 01 <--> /tmp/instance01
• 02 <--> /tmp/instance02
• 03 <--> /tmp/instance03

为简化场景，假设这3个目录创建于NAS中，且NAS已挂载至所有运行Nomad客户端节点的服务器，所有组/任务均拥有这3个目录的读写权限。

问题描述 #

我可通过以下几种方式配置服务读写状态数据的目录：

• 命令行参数
• 通过环境变量配置文件
• 通过Nomad模板插值的Template块

如何为组内不同实例运行的同一任务传递不同值？

即：如何为每个实例分配唯一且一致的标识，以便可靠识别？

已考虑方案 #

• Parameterized Block --> 不适用于Service类型作业
• Template Block --> 所有任务实例会接收相同数据
• Env Var --> 所有任务实例会接收相同数据
• Meta Block --> 所有任务实例会接收相同数据
• Variable Block --> 所有任务实例会接收相同数据
• Dynamic Block --> 可行方案，但本质是重复Group块
• Repeating Group Block --> 尽量避免此方案
• Multiple Job Spec --> 尽量避免此方案

Nomad支持在单个任务内循环，但似乎不支持跨任务循环。

欢迎任何解决方案，即使是临时方案。感谢！

作业配置示例 #

job "app-write" {
  datacenters = ["dc1"]
  type = "service"
  node_pool = "default"

  # Write
  group "app-write" {
    count = 3
    
    # /tmp/instance01
    volume "app01" {
      type = "host"
      read_only = false
      source = "tmpapp01"
    }

    # /tmp/instance02
    volume "app02" {
      type = "host"
      read_only = false
      source = "tmpapp02"
    }

    # /tmp/instance03
    volume "app03" {
      type = "host"
      read_only = false
      source = "tmpapp03"
    }
    
    network {
      port "http" { }  // 3100
      port "grpc" { } // 9095
      port "gossip" { }  // 7946
      # port "lb" { static = 8080 }
    }

    service {
      name = "app-write"
      address_mode = "host"
      port = "http"
      tags = ["http"]
      provider = "nomad"
    }

    service {
      name = "app-write"
      address_mode = "host"
      port = "grpc"
      tags = ["grpc"]
      provider = "nomad"
    }

    service {
      name = "app-write"
      address_mode = "host"
      port = "gossip"
      tags = ["gossip"]
      provider = "nomad"
    }

    task "app-write" {
      driver = "exec" # or "raw_exec"
      
      volume_mount {
        volume = "app01"
        destination = "/tmp/app01"
        read_only = false
      }

      volume_mount {
        volume = "app02"
        destination = "/tmp/app02"
        read_only = false
      }

      volume_mount {
        volume = "app03"
        destination = "/tmp/app03"
        read_only = false
      }

      config {
        command = "/usr/bin/app"
        args = [
          "-config.file=local/app/config.yaml",
          "-working-directory=/tmp/app01" # <-- Need this to change for each instance
          ]
      }

      resources {
        cpu = 100
        memory = 128
      }

      # Can change this for each instance too
      template {
        source = "/etc/app/config.yaml.tpl"
        destination = "local/app/config.yaml"
        change_mode = "restart" // restart
      }
    }
  }
}

内容的提问来源于stack exchange，提问作者Yeile