amazon-web-services - 在AWS中按比例缩小Auto Scaling组会导致永久警报

Question

我目前正在使用两个扩展策略，这些策略已附加到我的自动扩展组中:
一种

调用CloudWatch警报时将调用的扩展策略。此CloudWatch警报使用CPUUtilization指标，并在超过80％的CPU上触发。

另一个是按比例缩小策略，该策略在调用其他CloudWatch警报时被调用。此CloudWatch警报使用CPUUtilization指标，并在CPU低于50％时触发。

这种方法的副作用是，当我的ASG实例处于空闲状态(完全按比例缩小，没有处理发生)时，我的ASG处于警报状态。

有没有办法对此进行不同的设置，以使我的ASG不会处于持续发出警报的状态？

以下是来自CloudFormation模板的这些警报的一部分:

"ScaleUpPolicy" : {
  "Type" : "AWS::AutoScaling::ScalingPolicy",
  "Properties" : {
    "AdjustmentType" : "ChangeInCapacity",
    "AutoScalingGroupName" : { "Ref" : "WebApplicationASG" },
    "Cooldown" : "1",
    "ScalingAdjustment" : "1"
  }
},
"CPUAlarmHigh": {
  "Type": "AWS::CloudWatch::Alarm",
  "Properties": {
    "EvaluationPeriods": "1",
    "Statistic": "Average",
    "Threshold": "80",
    "AlarmDescription": "Alarm if CPU too high or metric disappears indicating instance is down",
    "Period": "60",
    "AlarmActions": [ { "Ref": "ScaleUpPolicy" } ],
    "Namespace": "AWS/EC2",
    "Dimensions": [ {
      "Name": "AutoScalingGroupName",
      "Value": { "Ref": "WebApplicationASG" }
    } ],
    "ComparisonOperator": "GreaterThanThreshold",
    "MetricName": "CPUUtilization"
  }
},
"ScaleDownPolicy" : {
  "Type" : "AWS::AutoScaling::ScalingPolicy",
  "Properties" : {
    "AdjustmentType" : "ChangeInCapacity",
    "AutoScalingGroupName" : { "Ref" : "WebApplicationASG" },
    "Cooldown" : "1",
    "ScalingAdjustment" : "-1"
  }
},
"CPUAlarmLow": {
  "Type": "AWS::CloudWatch::Alarm",
  "Properties": {
    "EvaluationPeriods": "1",
    "Statistic": "Average",
    "Threshold": "50",
    "AlarmDescription": "Alarm if CPU is low, causing scale down",
    "Period": "60",
    "AlarmActions": [ { "Ref": "ScaleDownPolicy" } ],
    "Namespace": "AWS/EC2",
    "Dimensions": [ {
      "Name": "AutoScalingGroupName",
      "Value": { "Ref": "WebApplicationASG" }
    } ],
    "ComparisonOperator": "LessThanThreshold",
    "MetricName": "CPUUtilization"
  }
},

Answer 1

这是正常的和预期的行为。

将指标设置为警报状态不是问题-请记住，触发事件的警报状态的变化是。因此，大概在您的按比例放大触发器触发警报时，按比例缩小便会退出警报状态。然后，当指标下降时，它将返回到警报状态，并触发缩减事件。