---
AWSTemplateFormatVersion: 2010-09-09

Description: Reference Architecture to host WordPress on AWS - Creates EFS alarms

Metadata:

  Authors:
    Description: Darryl Osborne (darrylo@amazon.com)
  License:
    Description: 'Copyright 2018 Amazon.com, Inc. and its affiliates. All Rights Reserved.
                  SPDX-License-Identifier: MIT-0'

  AWS::CloudFormation::Interface:

    ParameterGroups:
    - Label:
        default: Amazon EFS Parameters
      Parameters:
        - ElasticFileSystem
        - WarningThreshold
        - CriticalThreshold        
        - EmailAddress
        - InstanceType
        - EC2KeyName
        - SecurityGroup
        - NumberOfSubnets
        - Subnet
    ParameterLabels:
      CriticalThreshold:
        default: Burst Credit Balance Critical Threshold (Minutes)
      ElasticFileSystem:
        default: Amazon EFS File System
      EmailAddress:
        default: SNS Email Address
      InstanceType:
        default: Instance Type
      EC2KeyName:
        default: Existing Key Pair
      NumberOfSubnets:
        default: Number of subnets
      SecurityGroup:
        default: EFS Security Group
      Subnet:
        default: Subnets
      WarningThreshold:
        default: Burst Credit Balance Warning Threshold (Minutes)

Parameters:

  CriticalThreshold:
    AllowedPattern: ^[0-9]+$
    ConstraintDescription: Must be an integer.
    Default: 60
    Description: Send critical alarm this minutes before burst credit balance is zero.
    Type: String
  SecurityGroup:
    Description: Select the Amazon EFS security group.
    Type: AWS::EC2::SecurityGroup::Id  
  ElasticFileSystem:
    Description: The Amazon EFS file system id.
    Type: String
  EmailAddress:
    Description: The email address for SNS notifications.
    Type: String
  InstanceType:
    AllowedValues:
      - t3.nano
      - t3.micro
      - t3.small
      - t3.medium
    ConstraintDescription: Must be a valid Amazon EC2 instance type.
    Default: t3.nano
    Description: The Amazon EC2 instance type that dynamically adjusts thresholds based on permitted throughput changes.
    Type: String
  EC2KeyName:
    Description: Name of an existing EC2 key pair
    Type: AWS::EC2::KeyPair::KeyName
  NumberOfSubnets:
    AllowedValues:
    - 2
    - 3
    - 4
    - 5
    - 6
    Default: 3
    Description: Number of subnets. This must match your selections in the list of Subnets below.
    Type: String  
  Subnet:
    Description: Select existing subnets.
    Type: List<AWS::EC2::Subnet::Id>
  WarningThreshold:
    AllowedPattern: ^[0-9]+$
    ConstraintDescription: Must be an integer.
    Default: 180
    Description: Send warning alarm this many minutes before burst credit balance is zero.
    Type: String

Conditions:
  
  NumberOfSubnets1:
      !Equals [ 1, !Ref NumberOfSubnets ]
  NumberOfSubnets2:
      !Equals [ 2, !Ref NumberOfSubnets ]
  NumberOfSubnets3:
      !Equals [ 3, !Ref NumberOfSubnets ]
  NumberOfSubnets4:
      !Equals [ 4, !Ref NumberOfSubnets ]
  NumberOfSubnets5:
      !Equals [ 5, !Ref NumberOfSubnets ]
  NumberOfSubnets6:
      !Equals [ 6, !Ref NumberOfSubnets ]
  Subnet0: !Or
    - !Condition NumberOfSubnets1
    - !Condition NumberOfSubnets2
    - !Condition NumberOfSubnets3
    - !Condition NumberOfSubnets4
    - !Condition NumberOfSubnets5
    - !Condition NumberOfSubnets6
  Subnet1: !Or
    - !Condition NumberOfSubnets2
    - !Condition NumberOfSubnets3
    - !Condition NumberOfSubnets4
    - !Condition NumberOfSubnets5
    - !Condition NumberOfSubnets6
  Subnet2: !Or
    - !Condition NumberOfSubnets3
    - !Condition NumberOfSubnets4
    - !Condition NumberOfSubnets5
    - !Condition NumberOfSubnets6
  Subnet3: !Or
    - !Condition NumberOfSubnets4
    - !Condition NumberOfSubnets5
    - !Condition NumberOfSubnets6
  Subnet4: !Or
    - !Condition NumberOfSubnets5
    - !Condition NumberOfSubnets6
  Subnet5: !Condition NumberOfSubnets6

Mappings:

  RegionMap:
    ap-northeast-1:
      AMI: ami-0de5311b2a443fb89
    ap-northeast-2:
      AMI: ami-09cf633fe86e51bf0
    ap-south-1:
      AMI: ami-0e6329e222e662a52
    ap-southeast-1:
      AMI: ami-094bbd9e922dc515d
    ap-southeast-2:
      AMI: ami-02a66f06b3557a897
    ca-central-1:
      AMI: ami-088d4832275406edf
    eu-central-1:
      AMI: ami-070b208e993b59cea
    eu-west-1:
      AMI: ami-0ee415e1b8b71305f
    eu-west-2:
      AMI: ami-0648ea225c13e0729
    sa-east-1:
      AMI: ami-0122c4b16734197ac
    us-east-1:
      AMI: ami-09d3b3274b6c5d4aa
    us-east-2:
      AMI: ami-089a545a9ed9893b6
    us-west-1:
      AMI: ami-017c001a88dd93847
    us-west-2:
      AMI: ami-0d593311db5abb72b

Resources:

  AutoScalingGroup:
    Type: AWS::AutoScaling::AutoScalingGroup
    Properties:
      Cooldown: 60
      HealthCheckGracePeriod: 120
      HealthCheckType: EC2
      LaunchConfigurationName: !Ref LaunchConfiguration
      MaxSize: 1
      MinSize: 0
      DesiredCapacity: 1
      Tags:
        - Key: Name
          Value: !Join [ '', [ 'Updating ', !Ref 'ElasticFileSystem', ' burst credit balance Cloudwatch alarms.. will auto terminate' ] ]
          PropagateAtLaunch: true
      VPCZoneIdentifier:
        !If
          [ NumberOfSubnets1,
          [ !Select [ 0, !Ref Subnet ] ],
          !If
            [ NumberOfSubnets2,
            [ !Select [ 0, !Ref Subnet ], !Select [ 1, !Ref Subnet ] ],
            !If
              [ NumberOfSubnets3,
              [ !Select [ 0, !Ref Subnet ], !Select [ 1, !Ref Subnet ], !Select [ 2, !Ref Subnet ] ],
              !If
                [ NumberOfSubnets4,
                [ !Select [ 0, !Ref Subnet ], !Select [ 1, !Ref Subnet ], !Select [ 2, !Ref Subnet ], !Select [ 3, !Ref Subnet ] ],
                !If
                  [ NumberOfSubnets5,
                  [ !Select [ 0, !Ref Subnet ], !Select [ 1, !Ref Subnet ], !Select [ 2, !Ref Subnet ], !Select [ 3, !Ref Subnet ], !Select [ 4, !Ref Subnet ] ],
                  [ !Select [ 0, !Ref Subnet ], !Select [ 1, !Ref Subnet ], !Select [ 2, !Ref Subnet ], !Select [ 3, !Ref Subnet ], !Select [ 4, !Ref Subnet ], !Select [ 5, !Ref Subnet ] ]
                  ]
                ]
              ]
            ]
          ]
    CreationPolicy:
      ResourceSignal:
        Count: 0
        Timeout: PT5M
  AutoScalingPolicy:
    Type: AWS::AutoScaling::ScalingPolicy
    Properties:
      AdjustmentType: ChangeInCapacity
      AutoScalingGroupName: !Ref AutoScalingGroup
      Cooldown: 60
      PolicyType: SimpleScaling
      ScalingAdjustment: 1
  BurstCreditBalanceDecreaseAlarm:
    Type: AWS::CloudWatch::Alarm
    Properties:
      AlarmActions:
      - !Ref SNSTopic
      - !Ref AutoScalingPolicy
      AlarmDescription: !Join [ '', [ 'Set ', !Ref ElasticFileSystem, ' burst credit balance decrease threshold - ',  !Ref 'AWS::StackName' ] ]
      AlarmName: !Join [ '', [ 'Set ', !Ref ElasticFileSystem, ' burst credit balance decrease threshold - ', !Ref 'AWS::StackName'  ] ]
      ComparisonOperator: LessThanThreshold
      Dimensions:
      - Name: FileSystemId
        Value: !Ref ElasticFileSystem
      EvaluationPeriods: 10
      MetricName: PermittedThroughput
      Namespace: AWS/EFS
      Period: 60
      Statistic: Sum
      Threshold: 0
      TreatMissingData: missing
  BurstCreditBalanceIncreaseAlarm:
    Type: AWS::CloudWatch::Alarm
    DependsOn: BurstCreditBalanceDecreaseAlarm
    Properties:
      AlarmActions:
      - !Ref SNSTopic
      - !Ref AutoScalingPolicy
      AlarmDescription: !Join [ '', [ 'Set ', !Ref ElasticFileSystem, ' burst credit balance increase threshold - ',  !Ref 'AWS::StackName' ] ]
      AlarmName: !Join [ '', [ 'Set ', !Ref ElasticFileSystem, ' burst credit balance increase threshold - ', !Ref 'AWS::StackName'  ] ]
      ComparisonOperator: LessThanThreshold
      Dimensions:
      - Name: FileSystemId
        Value: !Ref ElasticFileSystem
      EvaluationPeriods: 10
      MetricName: PermittedThroughput
      Namespace: AWS/EFS
      Period: 60
      Statistic: Sum
      Threshold: 0
      TreatMissingData: missing
  CriticalAlarm:
    Type: AWS::CloudWatch::Alarm
    Properties:
      AlarmActions:
      - !Ref SNSTopic
      AlarmDescription: !Join [ '', [ !Ref ElasticFileSystem, ' burst credit balance - Critical - ',  !Ref 'AWS::StackName' ] ]
      AlarmName: !Join [ '', [ !Ref ElasticFileSystem, ' burst credit balance - Critical - ',  !Ref 'AWS::StackName' ] ]
      ComparisonOperator: LessThanThreshold
      Dimensions:
      - Name: FileSystemId
        Value: !Ref ElasticFileSystem
      EvaluationPeriods: 10
      MetricName: BurstCreditBalance
      Namespace: AWS/EFS
      Period: 60
      Statistic: Sum
      Threshold: 0
      TreatMissingData: missing
  InstanceProfile:
    Type: AWS::IAM::InstanceProfile
    Properties:
      Path: /
      Roles:
      - !Ref InstanceRole
  InstanceRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Version: 2012-10-17
        Statement:
        - Effect: Allow
          Principal:
            Service:
            - ec2.amazonaws.com
          Action:
          - sts:AssumeRole
      Path: /
      Policies:
      - PolicyName: efs-burst-credit-balance-cloudwatch-alarms
        PolicyDocument:
          Version: 2012-10-17
          Statement:
          - Effect: Allow
            Action:
              - cloudwatch:GetMetricStatistics
              - cloudwatch:PutMetricAlarm
              - autoscaling:DescribeAutoScalingGroups
              - autoscaling:DescribeAutoScalingInstances
              - autoscaling:DescribePolicies
              - autoscaling:UpdateAutoScalingGroup
              - elasticfilesystem:DescribeFileSystems
            Resource: '*'
          - Effect: Allow
            Action:
              - sns:Publish
            Resource: !Ref SNSTopic
  LaunchConfiguration:
    Type: AWS::AutoScaling::LaunchConfiguration
    DependsOn: WarningAlarm
    Metadata:
      AWS::CloudFormation::Init:
        configSets:
          set_cloudwatch_alarms:
            - set-cloudwatch-alarms
        set-cloudwatch-alarms:
          files:              
            /tmp/set-cloudwatch-alarms.sh:
              content:
                !Join [
                  "",[
                    "#!/bin/bash -x\n",
                    "\n",
                    "FILE_SYSTEM_ID=$1\n",
                    "WARNING_THRESHOLD_MINUTES=$2\n",
                    "CRITICAL_THRESHOLD_MINUTES=$3\n",
                    "SNS_ARN=$4\n",
                    "\n",
                    "error=0\n",
                    "\n",
                    "# get region\n",
                    "availability_zone=$(curl -s http://169.254.169.254/latest/meta-data/placement/availability-zone)\n",
                    "region=${availability_zone:0:-1}\n",
                    "\n",
                    "# get instance id\n",
                    "instance_id=$(curl -s http://169.254.169.254/latest/meta-data/instance-id)\n",
                    "\n",
                    "# get autoscaling group name\n",
                    "asg_name=$(aws autoscaling describe-auto-scaling-instances --instance-ids ${instance_id} --region ${region} --output text --query 'AutoScalingInstances[0].AutoScalingGroupName')\n",
                    "\n",
                    "# get autoscaling policy arn\n",
                    "asg_policy_arn=$(aws autoscaling describe-policies --auto-scaling-group-name ${asg_name} --region ${region} --output text --query 'ScalingPolicies[0].PolicyARN')\n",
                    "\n",
                    "# validate FILE_SYSTEM_ID send notification and exit if doesn't exist\n",
                    "aws efs describe-file-systems --file-system-id ${FILE_SYSTEM_ID} --region ${region} --output text --query 'FileSystems[0].[FileSystemId]'\n",
                    "result=$?\n",
                    "if [ $result -ne 0 ]; then\n",
                    "   aws sns publish --topic-arn ${SNS_ARN} --region ${region} --message 'Amazon EFS burst credit balance CloudWatch alarm error. File system '${FILE_SYSTEM_ID}' does not exist.'\n",
                    "   exit\n",
                    "fi\n",
                    "\n",
                    "# get current permitted throughput\n",
                    "count=1\n",
                    "while [ -z ${permitted_throughput} ] || [ ${permitted_throughput} == null ] && [ ${count} -lt 60 ]; do\n",
                    "   permitted_throughput=$(aws cloudwatch get-metric-statistics --namespace AWS/EFS --metric-name PermittedThroughput --dimensions Name=FileSystemId,Value=${FILE_SYSTEM_ID} --start-time $(date --utc +%FT%TZ -d '-120 seconds') --end-time $(date --utc +%FT%TZ -d '-60 seconds') --period 60 --statistics Sum --region ${region} --output json --query 'Datapoints[0].Sum')\n",
                    "   sleep 2\n",
                    "   count=$(expr ${count} + 1)\n",
                    "done\n",
                    "\n",
                    "# get current burst credit balance\n",
                    "count=1\n",
                    "while [ -z ${burst_credit_balance} ] || [ ${burst_credit_balance} == null ] && [ ${count} -lt 60 ]; do\n",
                    "   burst_credit_balance=$(aws cloudwatch get-metric-statistics --namespace AWS/EFS --metric-name BurstCreditBalance --dimensions Name=FileSystemId,Value=${FILE_SYSTEM_ID} --start-time $(date --utc +%FT%TZ -d '-120 seconds') --end-time $(date --utc +%FT%TZ -d '-60 seconds') --period 60 --statistics Sum --region ${region} --output json --query 'Datapoints[0].Sum')\n",
                    "   sleep 2\n",
                    "   count=$(expr ${count} + 1)\n",
                    "done\n",
                    "\n",
                    "# calculate new burst credit balance warning threshold\n",
                    "burst_credit_balance_threshold_warning=$(( ${burst_credit_balance:0:-2} - ( ( ( ${burst_credit_balance:0:-2} / ( ${permitted_throughput:0:-2} * 60 ) ) - $WARNING_THRESHOLD_MINUTES ) * ( ${permitted_throughput:0:-2} * 60 ) ) ))\n",
                    "\n",
                    "# calculate new burst credit balance critical threshold\n",
                    "burst_credit_balance_threshold_critical=$(( ${burst_credit_balance:0:-2} - ( ( ( ${burst_credit_balance:0:-2} / ( ${permitted_throughput:0:-2} * 60 ) ) - $CRITICAL_THRESHOLD_MINUTES ) * ( ${permitted_throughput:0:-2} * 60 ) ) ))\n",
                    "\n",                    
                    "# update warning alarm with new burst credit balance warning threshold\n",
                    "aws cloudwatch put-metric-alarm --alarm-name ''${FILE_SYSTEM_ID}' burst credit balance - Warning - '", !Ref 'AWS::StackName', " --alarm-description ''${FILE_SYSTEM_ID}' burst credit balance - Warning - '", !Ref 'AWS::StackName', " --actions-enabled --alarm-actions ${SNS_ARN} --metric-name BurstCreditBalance --namespace AWS/EFS --statistic Sum --dimensions Name=FileSystemId,Value=${FILE_SYSTEM_ID} --period 60 --evaluation-periods 5 --threshold ${burst_credit_balance_threshold_warning} --comparison-operator LessThanThreshold --treat-missing-data missing --region ${region}\n",
                    "result=$?\n",
                    "if [ $result -ne 0 ]; then\n",
                    "   aws sns publish --topic-arn ${SNS_ARN} --region ${region} --message 'Amazon EFS burst credit balance CloudWatch alarm error. Check CloudWatch alarms for file system '${FILE_SYSTEM_ID}'.'\n",
                    "   error=$(expr ${error} + 1)\n",
                    "fi\n",
                    "\n",
                    "# update critical alarm with new burst credit balance critical threshold\n",
                    "aws cloudwatch put-metric-alarm --alarm-name ''${FILE_SYSTEM_ID}' burst credit balance - Critical - '", !Ref 'AWS::StackName', " --alarm-description ''${FILE_SYSTEM_ID}' burst credit balance - Critical - '", !Ref 'AWS::StackName', " --actions-enabled --alarm-actions ${SNS_ARN} --metric-name BurstCreditBalance --namespace AWS/EFS --statistic Sum --dimensions Name=FileSystemId,Value=${FILE_SYSTEM_ID} --period 60 --evaluation-periods 5 --threshold ${burst_credit_balance_threshold_critical} --comparison-operator LessThanThreshold --treat-missing-data missing --region ${region}\n",
                    "result=$?\n",
                    "if [ $result -ne 0 ]; then\n",
                    "   aws sns publish --topic-arn ${SNS_ARN} --region ${region} --message 'Amazon EFS burst credit balance CloudWatch alarm error. Check CloudWatch alarms for file system '${FILE_SYSTEM_ID}'.'\n",
                    "   error=$(expr ${error} + 1)\n",
                    "fi\n",
                    "\n",
                    "# update burst credit balance increase threshold based\n",
                    "aws cloudwatch put-metric-alarm --alarm-name 'Set '${FILE_SYSTEM_ID}' burst credit balance increase threshold - '", !Ref 'AWS::StackName', " --alarm-description 'Set '${FILE_SYSTEM_ID}' burst credit balance increase threshold - '", !Ref 'AWS::StackName', " --actions-enabled --alarm-actions ${SNS_ARN} ${asg_policy_arn} --metric-name PermittedThroughput --namespace AWS/EFS --statistic Sum --dimensions Name=FileSystemId,Value=${FILE_SYSTEM_ID} --period 60 --evaluation-periods 5 --threshold ${permitted_throughput:0:-2} --comparison-operator GreaterThanThreshold --treat-missing-data missing --region ${region}\n",
                    "result=$?\n",
                    "if [ $result -ne 0 ]; then\n",
                    "   aws sns publish --topic-arn ${SNS_ARN} --region ${region} --message 'Amazon EFS burst credit balance CloudWatch alarm error. Check CloudWatch alarms for file system '${FILE_SYSTEM_ID}'.'\n",
                    "   error=$(expr ${error} + 1)\n",
                    "fi\n",
                    "\n",
                    "# update burst credit balance decrease threshold based\n",
                    "aws cloudwatch put-metric-alarm --alarm-name 'Set '${FILE_SYSTEM_ID}' burst credit balance decrease threshold - '", !Ref 'AWS::StackName', " --alarm-description 'Set '${FILE_SYSTEM_ID}' burst credit balance decrease threshold - '", !Ref 'AWS::StackName', " --actions-enabled --alarm-actions ${SNS_ARN} ${asg_policy_arn} --metric-name PermittedThroughput --namespace AWS/EFS --statistic Sum --dimensions Name=FileSystemId,Value=${FILE_SYSTEM_ID} --period 60 --evaluation-periods 5 --threshold ${permitted_throughput:0:-2} --comparison-operator LessThanThreshold --treat-missing-data missing --region ${region}\n",
                    "result=$?\n",
                    "if [ $result -ne 0 ]; then\n",
                    "   aws sns publish --topic-arn ${SNS_ARN} --region ${region} --message 'Amazon EFS burst credit balance CloudWatch alarm error. Check CloudWatch alarms for file system '${FILE_SYSTEM_ID}'.'\n",
                    "   error=$(expr ${error} + 1)\n",
                    "fi\n",
                    "\n",
                    "# auto terminate instance - setting auto scaling group desired capacity 0\n",
                    "if [ $error -eq 0 ]; then\n",
                    "   aws autoscaling update-auto-scaling-group --auto-scaling-group-name ${asg_name} --desired-capacity 0 --region ${region}\n",
                    "   else\n",
                    "   aws sns publish --topic-arn ${SNS_ARN} --region ${region} --message 'Amazon EFS burst credit balance CloudWatch alarm error. Check CloudWatch alarms for file system '${FILE_SYSTEM_ID}'.'\n",
                    "fi\n",
                    "\n"                    
                  ]
                ]
              mode: 000777
              owner: root
              group: root             
    Properties:
      BlockDeviceMappings:
        - DeviceName: /dev/xvda
          Ebs:
            DeleteOnTermination: true
            VolumeSize: 10
            VolumeType: gp2
      IamInstanceProfile: !Ref InstanceProfile
      ImageId: !FindInMap [ RegionMap, !Ref 'AWS::Region', AMI ]
      InstanceMonitoring: true
      InstanceType: !Ref InstanceType
      KeyName: !Ref EC2KeyName
      SecurityGroups:
      - !Ref SecurityGroup
      UserData:
        "Fn::Base64":
          !Sub |
            #cloud-config
            repo_update: true
            repo_upgrade: all

            packages:

            runcmd:
            - ntpstat
            - /opt/aws/bin/cfn-init --configsets set_cloudwatch_alarms --verbose --stack ${AWS::StackName} --resource LaunchConfiguration --region ${AWS::Region}
            - /tmp/set-cloudwatch-alarms.sh ${ElasticFileSystem} ${WarningThreshold} ${CriticalThreshold} ${SNSTopic}
  SNSTopic: 
    Type: AWS::SNS::Topic
    Properties: 
      DisplayName: !Join [ '', [ !Ref ElasticFileSystem, '-alarm-notification' ] ]
      KmsMasterKeyId: String
      Subscription:
      - Endpoint: !Ref EmailAddress
        Protocol: "email"
      TopicName: !Join [ '', [ !Ref ElasticFileSystem, '-alarm-notification' ] ]
  WarningAlarm:
    Type: AWS::CloudWatch::Alarm
    DependsOn: CriticalAlarm
    Properties:
      AlarmActions:
      - !Ref SNSTopic
      AlarmDescription: !Join [ '', [ !Ref ElasticFileSystem, ' burst credit balance - Warning - ',  !Ref 'AWS::StackName' ] ]
      AlarmName: !Join [ '', [ !Ref ElasticFileSystem, ' burst credit balance - Warning - ',  !Ref 'AWS::StackName' ] ]
      ComparisonOperator: LessThanThreshold
      Dimensions:
      - Name: FileSystemId
        Value: !Ref ElasticFileSystem
      EvaluationPeriods: 10
      MetricName: BurstCreditBalance
      Namespace: AWS/EFS
      Period: 60
      Statistic: Sum
      Threshold: 0
      TreatMissingData: missing

Outputs:
  BurstCreditBalanceDecreaseAlarmArn:
    Value: !GetAtt BurstCreditBalanceDecreaseAlarm.Arn
  BurstCreditBalanceIncreaseAlarmArn:
    Value: !GetAtt BurstCreditBalanceIncreaseAlarm.Arn
  CriticalAlarmArn:
    Value: !GetAtt CriticalAlarm.Arn
  WarningAlarmArn:
    Value: !GetAtt WarningAlarm.Arn