如何移除ECS CloudWatch Dashboard中集群名的[]符号（字符串列表必填）

我正在为ECS创建CloudWatch Dashboard，但由于变量采用字符串列表类型，负载均衡器名称出现了形如[ "mis-app-cluster" ]的[]符号。请问是否有方法可以移除该符号？注：字符串列表为必填项。

配置数据 #

{
     my-dashboard-name = "MIS-Dev-Cloudwatch-Dashboard-ECS"
     aws-region        = "eu-west-1"
     targets           = ["mis-app-cluster"]
     metrics           = ["CPUUtilization", "MemoryUtilization"]
     service_name      =   ["mis-fileserver", "mis-nginx", "mis-odi", "mis-oraclebi", "mis-ords", "mis-restdataservices"]
     aws-namespace     = "AWS/ECS"
     dim               = "ClusterName"
     stat              = "Average"
     period            = 300
}

ALB模块代码 #

locals {

  widget-def-alb = [for metric in var.metrics :
    {
      type   = "metric",
      x      = 0,
      y      = 0
      width  = 18,
      height = 8,
      properties = {
        metrics = [for targetgroup in var.target_groups : [var.aws-namespace, metric,"TargetGroup", targetgroup, var.dim, var.targets]],
        title = "${var.aws-namespace}: ${metric}",
        region  = var.aws-region,
        period  = var.period,
        stat    = var.stat,
        view    = "timeSeries",
        legend = {
          position = "right"
        }
      }
    }
  ]
}

resource "aws_cloudwatch_dashboard" "cw-dashboard-alb" {
  count = var.aws-namespace == "AWS/ApplicationELB" ? 1 : 0
  dashboard_name = var.dashboard-name

  dashboard_body = jsonencode({
    start   = "-PT9H"
    widgets = local.widget-def-alb
  })
}

模块调用代码 #

module "create-dashboard" {
  source         = "../"
  for_each       = { for service in local.dashboards : service.my-dashboard-name => service if length(regexall(".*ALB.*", service.my-dashboard-name)) > 0 }
  dashboard-name = each.value.my-dashboard-name
  aws-region     = each.value.aws-region
  targets        = each.value.targets
  metrics        = each.value.metrics
  aws-namespace  = each.value.aws-namespace
  dim            = each.value.dim
  target_groups  = each.value.target_groups
  stat           = each.value.stat
  period         = each.value.period
}

当前输出结果 #

{
    "legend": {
        "position": "right"
    },
    "metrics": [
        [ "AWS/ECS", "CPUUtilization", "ServiceName", "mis-fileserver", "ClusterName", [ "mis-app-cluster" ] ],
        [ ".", "MemoryUtilization", ".", ".", ".", [ "mis-app-cluster" ] ]
    ],
    "period": 300,
    "region": "eu-west-1",
    "stat": "Average",
    "title": "mis-fileserver",
    "view": "timeSeries",
    "timezone": "UTC"
}

解决方案 #

问题根源在于模块代码中直接将列表类型的var.targets传入了metrics数组，导致序列化为嵌套列表结构。针对你的场景，有两种处理方式：

方法1：提取列表单个元素（适配单元素必填列表） #

修改模块中widget-def-alb的metrics定义，将var.targets替换为var.targets[0]，直接取列表第一个元素作为字符串传入：

metrics = [for targetgroup in var.target_groups : [var.aws-namespace, metric,"TargetGroup", targetgroup, var.dim, var.targets[0]]],

修改后，输出中的[ "mis-app-cluster" ]会变为"mis-app-cluster"，符合CloudWatch指标的格式要求。

方法2：遍历多元素列表（适配未来多集群场景） #

如果后续targets可能包含多个集群名称，可以通过嵌套for循环生成对应指标条目，并用flatten展开嵌套数组：

metrics = flatten([for targetgroup in var.target_groups : 
  [for target in var.targets : [var.aws-namespace, metric,"TargetGroup", targetgroup, var.dim, target]]
]),

这种方式会为每个targetgroup和target的组合生成独立的指标条目，同时避免嵌套列表的问题。

内容的提问来源于stack exchange，提问作者DineshS