Serverless Framework example to restart fargate services based on memory usage

fargate-restart-serverless.yml

service: restartFargateServices
custom:
  # SNS topic where the CloudWatch alarms will send messages when triggered
  # We need the full Arn for the CloudFormation snippet that creates the alarms
  snsTopic: "${self:service}-fargate-memory-alarms"
  snsTopicArn: { "Fn::Join" : ["", ["arn:aws:sns:${self:provider.region}:", { "Ref" : "AWS::AccountId" }, ":${self:custom.snsTopic}" ] ]  }
  # Cluster and Service Fargate names that we want to monitor and restart
  cluster_name: "my-cluster"
  service_name: "my-service"

provider:
  name: aws
  runtime: ruby2.5

  stage: dev
  region: eu-west-1

  # We need our lambda to have permissions to update ECS services to restart them
  iamRoleStatements:
    - Effect: Allow
      Action:
        - ecs:UpdateService
      Resource: '*'

functions:
  restartFargateServices:
    handler: handler.restart_service

    # The lambda function will get invoked when a message is sent to the SNS topic
    events:
      - sns: ${self:custom.snsTopic}

resources:
 Resources:
   # Cloudformation template for the CloudWatch alarms
   MemoryUsageAlarm:
     Type: AWS::CloudWatch::Alarm
     Properties:
       # This will send a message to the SNS topic when the alarm triggers
       ActionsEnabled: true
       AlarmActions:
         - ${self:custom.snsTopicArn}
       AlarmName: ${self:service}:MemoryUsageAlarm
       ComparisonOperator: GreaterThanOrEqualToThreshold
       # Get the cluster and service name dimensions from the YML configuration on lines 8 and 9
       Dimensions:
         - Name: ClusterName
           Value: ${self:custom.cluster_name}
         - Name: ServiceName
           Value: ${self:custom.service_name}
       MetricName: MemoryUtilization
       Namespace: AWS/ECS
       # Trigger the alarm when memory usage goes over 85% for 2 periods of 120 seconds
       EvaluationPeriods: 2
       Period: 120
       Statistic: Maximum
       Threshold: 85.0