(事前にSNS側で通知を受けられるような準備はしておくこと)

.ebextensionにて以下を追加

packages:
  yum:
    perl-DateTime: []
    perl-Sys-Syslog: []
    perl-LWP-Protocol-https: []
    perl-Switch: []
    perl-URI: []
    perl-Bundle-LWP: []
files:
  /root/setup_alarm.sh:
    mode: "000755"
    owner: root
    group: root
    content: |
      #!/bin/bash
      INSTANCE_ID="`wget -qO- http://169.254.169.254/latest/meta-data/instance-id`"
      REGION="`curl --silent http://169.254.169.254/latest/dynamic/instance-identity/document | jq -r .region`"
      echo '*/5 * * * * root perl /opt/cloudwatch/aws-scripts-mon/mon-put-instance-data.pl `{"Fn::GetOptionSetting" : { "OptionName" : "CloudWatchMetrics", "DefaultValue" : "--mem-util --disk-space-util --disk-path=/" }}` >> /var/log/cwpump.log 2>&1' > /etc/cron.d/cwpump
      chmod 644 /etc/cron.d/cwpump
      chmod u+x /opt/cloudwatch/aws-scripts-mon/mon-put-instance-data.pl
      aws cloudwatch put-metric-alarm --region=$REGION --alarm-name WebDiskSpaceUtilization --alarm-description "Alarm when DiskSpaceUtilization exceeds 90 percent" --metric-name DiskSpaceUtilization --namespace System/Linux --statistic Average --period 300 --threshold 90 --comparison-operator GreaterThanThreshold  --dimensions Name=Filesystem,Value=/dev/nvme0n1p1 Name=MountPath,Value=/ Name=InstanceId,Value=$INSTANCE_ID --evaluation-periods 2 --alarm-actions #{SNSのARN} --unit Percent
      aws cloudwatch put-metric-alarm --region=$REGION --alarm-name WebMemoryUtilization --alarm-description "Alarm when MemoryUtilization exceeds 95 percent" --metric-name MemoryUtilization --namespace System/Linux --statistic Average --period 300 --threshold 95 --comparison-operator GreaterThanThreshold  --dimensions Name=InstanceId,Value=$INSTANCE_ID --evaluation-periods 2 --alarm-actions #{SNSのARN} --unit Percent
sources:
  /opt/cloudwatch: https://aws-cloudwatch.s3.amazonaws.com/downloads/CloudWatchMonitoringScripts-1.2.1.zip
container_commands:
  add-swap-space:
    command: "/bin/bash /root/setup_alarm.sh"
    ignoreErrors: true
option_settings:
  "aws:autoscaling:launchconfiguration" :
    IamInstanceProfile : "aws-elasticbeanstalk-ec2-role"
  "aws:elasticbeanstalk:customoption" :
    CloudWatchMetrics : "--mem-util --mem-used --mem-avail --disk-space-util --disk-space-used --disk-space-avail --disk-path=/ --auto-scaling"

IAMでRoles > aws-elasticbeanstalk-ec2-role の「Add inline policy」にて、下記のように設定して追加

Service: CloudWatch
Actions: PutMetricData と PutMetricAlarm を追加
Resources: Specific Add ARN にて例えば下記
- Region => ana
- Account => デフォルトのまま
- Alarm Name => any
Name: CloudWatchMetricAlarm など

これでデプロイしてCloudWatchの

System/Linux > InstanceID でメモリ使用量などが確認できる
System/Linux > AutoScalingGroupName, Filesystem, MountPath でディスク残量などが確認できる

Alarmで監視されていることを確認

参考: https://aws.amazon.com/jp/premiumsupport/knowledge-center/elastic-beanstalk-memory-monitoring/