使用 Terraform 创建的 CWAgent 指标警报不会收集数据点(停留在"数据不足"中)

Question

我已经使用 Terraform 为内存利用率创建了一个 CloudWatch 警报，但警报不会移动到OK状态(保持INSUFFICIENT_DATA(。但是，当我从 AWS 管理控制台手动创建具有相同确切配置的相同警报时，它变为OK状态，并且我看到了数据点。

我已经在尝试创建警报的 EC2 实例中成功安装了 CloudWatch 代理，我可以在 CloudWatch 指标部分看到指标。

我的地形代码：

resource "aws_cloudwatch_metric_alarm" "memory" {
  alarm_name = "memory-utilization-alarm-${var.env}"
  comparison_operator = "GreaterThanOrEqualToThreshold"
  evaluation_periods  = "1"
  metric_name = "mem_used_percent"
  namespace = "CWAgent"
  period = "300"
  statistic = "Average"
  threshold = "${var.alarms_memory_threshold}"
  alarm_description = "This metric monitors ec2 memory utilization"
  alarm_actions = [ "${aws_sns_topic.sns_topic.arn}" ]
  dimensions = {
    InstanceId = "${var.instance_id}"
    ImageId = "${var.ami_id}"
  }
  tags = {
    Environment = "${var.env}"
    Project = "${var.project}"
    Provisioner="cloudwatch"
    Name = "${local.name}.memory"
  }
}

描述使用 Terraform 创建的警报的 AWS CLI 输出：

aws cloudwatch describe-alarms --alarm-names memory-utilization-alarm-dev
{
    "MetricAlarms": [
        {
            "EvaluationPeriods": 1, 
            "TreatMissingData": "missing", 
            "AlarmArn": "arn:aws:cloudwatch:us-west-2:289914521333:alarm:memory-utilization-alarm-dev", 
            "StateUpdatedTimestamp": "2019-07-12T08:45:07.020Z", 
            "AlarmConfigurationUpdatedTimestamp": "2019-07-12T08:45:07.020Z", 
            "ComparisonOperator": "GreaterThanOrEqualToThreshold", 
            "AlarmActions": [
                "arn:aws:sns:us-west-2:289914521333:sns-topic"
            ], 
            "AlarmDescription": "This metric monitors ec2 memory utilization", 
            "Namespace": "CWAgent", 
            "Period": 300, 
            "StateValue": "INSUFFICIENT_DATA", 
            "Threshold": 80.0, 
            "AlarmName": "memory-utilization-alarm-dev", 
            "Dimensions": [
                {
                    "Name": "InstanceId", 
                    "Value": "i-03417f2d90d3dc6ca"
                }, 
                {
                    "Name": "ImageId", 
                    "Value": "ami-09d1383e2a5ae8a93"
                }
            ], 
            "Statistic": "Average", 
            "StateReason": "Unchecked: Initial alarm creation", 
            "InsufficientDataActions": [], 
            "OKActions": [], 
            "ActionsEnabled": true, 
            "MetricName": "mem_used_percent"
        }
    ]
}

描述使用 AWS 控制台创建的警报的 AWS CLI 输出：

aws cloudwatch describe-alarms --alarm-names memory-utilization-alarm
{
    "MetricAlarms": [
        {
            "Dimensions": [
                {
                    "Name": "InstanceId", 
                    "Value": "i-03417f2d90d3dc6ca"
                }, 
                {
                    "Name": "ImageId", 
                    "Value": "ami-09d1383e2a5ae8a93"
                }, 
                {
                    "Name": "InstanceType", 
                    "Value": "t3.large"
                }
            ], 
            "Namespace": "CWAgent", 
            "DatapointsToAlarm": 1, 
            "ActionsEnabled": true, 
            "MetricName": "mem_used_percent", 
            "EvaluationPeriods": 1, 
            "StateValue": "OK", 
            "StateUpdatedTimestamp": "2019-07-12T09:49:28.749Z", 
            "AlarmConfigurationUpdatedTimestamp": "2019-07-12T09:47:55.914Z", 
            "AlarmActions": [
                "arn:aws:sns:us-west-2:289914521333:sns-topic"
            ], 
            "InsufficientDataActions": [], 
            "AlarmArn": "arn:aws:cloudwatch:us-west-2:289914521333:alarm:memory-utilization-alarm", 
            "StateReasonData": "{"version":"1.0","queryDate":"2019-07-12T09:49:28.746+0000","startDate":"2019-07-12T09:44:00.000+0000","statistic":"Average","period":300,"recentDatapoints":[61.253520518958474],"threshold":80.0}", 
            "Threshold": 80.0, 
            "StateReason": "Threshold Crossed: 1 out of the last 1 datapoints [61.253520518958474 (12/07/19 09:44:00)] was not greater than or equal to the threshold (80.0) (minimum 1 datapoint for ALARM -> OK transition).", 
            "OKActions": [], 
            "AlarmDescription": "memory-utilization-alarm", 
            "Period": 300, 
            "ComparisonOperator": "GreaterThanOrEqualToThreshold", 
            "AlarmName": "memory-utilization-alarm", 
            "Statistic": "Average", 
            "TreatMissingData": "missing"
        }
    ]
}

Answer 1

来自 Cloudwatch Agent 的 mem_used_percent 指标有 3 个维度：InstanceId、ImageId 和 InstanceType 。AWS 用户指南中当前未列出每个指标的维度，但您可以使用以下 AWS CLI 命令找到这些维度：

$ aws cloudwatch list-metrics --namespace CWAgent --metric-name mem_used_percent --query 'Metrics[0].Dimensions[].Name'
[
    "InstanceId", 
    "ImageId", 
    "InstanceType"
]

要修复警报，您需要更改警报定义以包含InstanceType维度：

resource "aws_cloudwatch_metric_alarm" "memory" {
  alarm_name = "memory-utilization-alarm-${var.env}"
  comparison_operator = "GreaterThanOrEqualToThreshold"
  evaluation_periods  = "1"
  metric_name = "mem_used_percent"
  namespace = "CWAgent"
  period = "300"
  statistic = "Average"
  threshold = "${var.alarms_memory_threshold}"
  alarm_description = "This metric monitors ec2 memory utilization"
  alarm_actions = [ "${aws_sns_topic.sns_topic.arn}" ]
  dimensions = {
    InstanceId = "${var.instance_id}"
    ImageId = "${var.ami_id}"
    InstanceType = "${var.instance_type}"
  }
  tags = {
    Environment = "${var.env}"
    Project = "${var.project}"
    Provisioner="cloudwatch"
    Name = "${local.name}.memory"
  }
}