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AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31

Description: >
  This template creates the required resources for implementing an ECS monitoring solution. Please check the solution overview on this blog post: https://aws.amazon.com/blogs/containers/

Metadata:
  AWS::CloudFormation::Interface:
    ParameterLabels:
      EnableMonitoring:
        default: >
          Do you want to enable the monitoring solution?
      MonitorAllECSClusters:
        default: >
          Do you want to monitor all ECS Clusters within the region?
      MonitoringTagKeyValue:
        default: >
          Tag Value
      EnableEncryption:
        default: >
          Do you want to enable encryption for SQS and SNS?
      KMSAdminRole:
        default: >
          ARN for the KMS Key administrator.
      NotificationEmail:
        default: >
          Destination email for receiving notifications.
    ParameterGroups:
      -
        Label:
          default: "Monitoring configuration"
        Parameters:
          - EnableMonitoring
          - MonitorAllECSClusters
          - MonitoringTagKeyValue
          - NotificationEmail
      -
        Label:
          default: "Advanced settings"
        Parameters:
          - EnableEncryption
          - KMSAdminRole

Parameters:
  EnableMonitoring:
    Type: String
    Default: Yes
    Description: >
      Select 'true' if you want to enable the monitoring engine. Select 'false' if you want to stop the monitoring.
    AllowedValues:
      - Yes
      - No
  MonitorAllECSClusters:
    Type: String
    Default: Yes
    Description: >
      If you select 'true', all the ECS Clusters within the region will be monitored.
      If you select 'false', clusters you want to monitor must be tagged with Tag Name: 'ecs-agent-monitoring' and a custom Tag Value you must supply below. This allow you to deploy multiple instances of the solution
      for monitoring different Clusters and workloads.
    AllowedValues:
      - Yes
      - No
  MonitoringTagKeyValue:
    Type: String
    Default: ecs-monitoring-group-1
    Description: >
      If you prefer to monitor only tagged clusters, you must provide the Tag Value present in your ECS Clusters. The Tag Key is fixed to be 'ecs-agent-monitoring'.
      If you select 'true' in the option above, this value will be ignored and all the ECS Clusters within the region will be monitored.
    AllowedPattern: ^([\p{L}\p{Z}\p{N}_.:/=+\-@]*)$
    MinLength: 1
    MaxLength: 256
  EnableEncryption:
    Type: String
    Default: No
    Description: >
      Encryption at rest for the events sent to the SQS Queue and the SNS topic. If you enable it, you must provide a KMS admin role.
      Please note that encryption at rest for CloudWatch logs is always enabled via server-side encryption for the log data at rest. Enabling this will use your custom KMS key for CloudWatch logs as well.
    AllowedValues:
      - Yes
      - No
  KMSAdminRole:
    Type: String
    Default: ''
    Description: >
      (Required, if encryption is enabled) Admin user, group or role that will have full access to the CMK Encryption Key.
    AllowedPattern: ^$|^arn:(aws|aws-cn|aws-us-gov):iam::\d{12}:(role|user|group)/[a-zA-Z_0-9+=,.@-_/]{1,}$
  NotificationEmail:
    Type: String
    Description: >
      Email address or distribution list to notify.
    AllowedPattern: ^[a-zA-Z0-9]{1,}@[a-zA-Z0-9]{1,}\.[a-zA-Z]{1,}$

Mappings:
  LambdaSettingsMap:
    LambdaRuntime:
      value: python3.9
    LambdaTimeout:
      value: 300
  MonitoringConfig:
    expiredTTLseconds:
      value: 60
    logRetentionDays:
      value: 60
    MonitoringTagKeyName:
      value: ecs-agent-monitoring

Conditions:
  EnableEventRule: !Equals [!Ref EnableMonitoring, 'true']
  EncryptionCondition: !Equals [!Ref EnableEncryption, 'true']
  MonitorAllECSClustersRegardlessTags: !Equals [!Ref MonitorAllECSClusters, 'true']

Rules:
  checkIAMRoleForKMS:
    RuleCondition: !Equals
      - !Ref EnableEncryption
      - 'true'
    Assertions:
      - Assert: !Not
          - 'Fn::Equals':
              - ''
              - !Ref KMSAdminRole
        AssertDescription: Please specify a valid KMS administrator role, this property cannot be empty.

Resources:
  ECSEventBridgeECSAgentMonitorFunction:
    Type: AWS::Serverless::Function
    Metadata:
      cfn_nag:
        rules_to_suppress:
          - id: W89
            reason: Custom resource deployed on VPCs owned by the Lambda service.
    Properties:
      FunctionName: !Sub ${AWS::StackName}
      Role: !GetAtt ECSEventBridgeMonitorECSAgentExecutionRole.Arn
      CodeUri: code
      Handler: lambda_event_bridge_monitor.handler
      ReservedConcurrentExecutions: 1
      Runtime: !FindInMap
        - LambdaSettingsMap
        - LambdaRuntime
        - value
      Timeout: !FindInMap
        - LambdaSettingsMap
        - LambdaTimeout
        - value
      Environment:
        Variables:
          monitoringTagKeyName: !If
            - MonitorAllECSClustersRegardlessTags
            - !Ref 'AWS::NoValue'
            - !FindInMap
                - MonitoringConfig
                - MonitoringTagKeyName
                - value
          monitoringTagKeyValue: !If
            - MonitorAllECSClustersRegardlessTags
            - !Ref 'AWS::NoValue'
            - !Ref MonitoringTagKeyValue
          checkAllClusters: !If
            - MonitorAllECSClustersRegardlessTags
            - True
            - False
          sendEmailNotification: !Ref SNSMonitoringTopic
  ECSEventBridgeMonitorECSAgentLogGroup:
    Type: AWS::Logs::LogGroup
    Properties:
      LogGroupName: !Sub /aws/lambda/${ECSEventBridgeECSAgentMonitorFunction}
      RetentionInDays: !FindInMap
        - MonitoringConfig
        - logRetentionDays
        - value
      KmsKeyId: !If
        - EncryptionCondition
        - !GetAtt KMSCMKKey.Arn
        - !Ref AWS::NoValue
  AgentFailureMetricFilterCluster:
    Type: AWS::Logs::MetricFilter
    Properties:
      LogGroupName: !Ref ECSEventBridgeMonitorECSAgentLogGroup
      FilterPattern: '[loglvl = WARNING, timestamp, id, cluster, node]'
      MetricTransformations:
        -
          MetricValue: '1'
          Dimensions:
            - Key: ClusterName
              Value: $cluster
          MetricNamespace: ECS/ECSAgentFailures
          MetricName: ECSAgentFailuresCount
          Unit: Count
  AgentFailureMetricFilterNode:
    Type: AWS::Logs::MetricFilter
    Properties:
      LogGroupName: !Ref ECSEventBridgeMonitorECSAgentLogGroup
      FilterPattern: '[loglvl = WARNING, timestamp, id, cluster, node]'
      MetricTransformations:
        -
          MetricValue: '1'
          Dimensions:
            - Key: NodeName
              Value: $node
          MetricNamespace: ECS/ECSAgentFailures
          MetricName: ECSAgentFailuresCount
          Unit: Count
  ECSEventBridgeMonitorECSAgentExecutionRole:
    Type: AWS::IAM::Role
    Metadata:
      cfn_nag:
        rules_to_suppress:
          - id: W11
            reason: "Resource undetermined"
    Properties:
     AssumeRolePolicyDocument:
       Statement:
       - Action:
         - sts:AssumeRole
         Effect: Allow
         Principal:
           Service:
           - lambda.amazonaws.com
       Version: '2012-10-17'
     Path: "/"
     Policies:
     - PolicyName: !Sub ${AWS::StackName}-CW
       PolicyDocument:
         Statement:
         - Action:
           - logs:CreateLogGroup
           - logs:CreateLogStream
           - logs:PutLogEvents
           Effect: Allow
           Resource: arn:aws:logs:*:*:*
         Version: '2012-10-17'
     - PolicyName: !Sub ${AWS::StackName}-SNS
       PolicyDocument:
         Statement:
         - Action:
            - sns:Publish
           Effect: 'Allow'
           Resource: !Ref SNSMonitoringTopic
         Version: '2012-10-17'
     - PolicyName: !Sub ${AWS::StackName}-Checks
       PolicyDocument:
         Statement:
         - Action:
            - ec2:DescribeInstances
            - ecs:DescribeClusters
            - ecs:DescribeContainerInstances
           Effect: Allow
           Resource: '*'
         Version: '2012-10-17'
     - !If
        - EncryptionCondition
        - PolicyName: !Sub ${AWS::StackName}-KMS
          PolicyDocument:
            Statement:
            - Action:
                - kms:Encrypt
                - kms:Decrypt
                - kms:ReEncrypt
                - kms:GenerateDataKey
                - kms:Describe
              Effect: Allow
              Resource: !GetAtt KMSCMKKey.Arn
        - !Ref AWS::NoValue
     - PolicyName: !Sub ${AWS::StackName}-SQS
       PolicyDocument:
         Statement:
         - Action:
            - sqs:ReceiveMessage
            - sqs:DeleteMessage
            - sqs:GetQueueAttributes
           Effect: Allow
           Resource: !GetAtt ECSEventBridgeSQSQueue.Arn
     - PolicyName: !Sub ${AWS::StackName}-SSM
       PolicyDocument:
         Statement:
         - Action:
            - ssm:DescribeInstanceInformation
           Effect: Allow
           Resource: '*'
         Version: '2012-10-17'
  EventRule:
    Type: AWS::Events::Rule
    Properties:
      Description: Triggered when Amazon ECS Agent is disconnected
      EventPattern:
        source:
          - aws.ecs
        detail-type:
          - ECS Container Instance State Change
        detail:
          agentConnected:
            - false
          status:
            - ACTIVE
      State: !If
        - EnableEventRule
        - ENABLED
        - DISABLED
      Targets:
        - Arn: !GetAtt ECSEventBridgeSQSQueue.Arn
          Id: ECSAgentDisconnected
          RetryPolicy:
            MaximumRetryAttempts: 4
            MaximumEventAgeInSeconds: 60
  ECSEventBridgeSQSQueue:
    Type: AWS::SQS::Queue
    Properties:
      DelaySeconds: !FindInMap
          - MonitoringConfig
          - expiredTTLseconds
          - value
      VisibilityTimeout: !FindInMap
        - LambdaSettingsMap
        - LambdaTimeout
        - value
      MessageRetentionPeriod: 172800
      KmsMasterKeyId: !If
        - EncryptionCondition
        - !Ref KMSCMKKey
        - !Ref AWS::NoValue
      KmsDataKeyReusePeriodSeconds: !If
        - EncryptionCondition
        - 43200
        - !Ref AWS::NoValue
  KMSCMKKey:
    Type: AWS::KMS::Key
    Condition: EncryptionCondition
    Properties:
      Description: CMK for encrypting SQS, SNS and CloudWatch data
      EnableKeyRotation: true
      KeyPolicy:
        Version: '2012-10-17'
        Statement:
          - Sid: Allow EventBridge access
            Effect: Allow
            Principal:
              Service: events.amazonaws.com
            Action:
              - kms:GenerateDataKey
              - kms:Decrypt
            Resource: '*'
          - Sid: Allow SNS access
            Effect: Allow
            Principal:
              Service: sns.amazonaws.com
            Action:
              - kms:GenerateDataKey
              - kms:Decrypt
            Resource: '*'
          - Sid: Allow CloudWatch access
            Effect: Allow
            Principal:
              Service: !Sub logs.${AWS::Region}.amazonaws.com
            Action:
              - kms:Encrypt
              - kms:Decrypt
              - kms:ReEncrypt
              - kms:GenerateDataKey
              - kms:DescribeKey
            Resource: '*'
            Condition:
                ArnEquals:
                  kms:EncryptionContext:aws:logs:arn: !Sub arn:aws:logs:${AWS::Region}:${AWS::AccountId}:log-group:/aws/lambda/${AWS::StackName}
          - Sid: Allow access for Key Administrators
            Effect: Allow
            Principal:
              AWS:
                - !Sub arn:aws:iam::${AWS::AccountId}:root
                - !Ref KMSAdminRole
            Action:
              - kms:*
            Resource: '*'
  SQSPermissions:
    Type: AWS::SQS::QueuePolicy
    Properties:
      PolicyDocument:
        Statement:
        - Effect: Allow
          Principal:
            Service: events.amazonaws.com
          Action:
            - sqs:SendMessage
          Resource: !GetAtt ECSEventBridgeSQSQueue.Arn
          Condition:
            ArnEquals:
              aws:SourceArn: !GetAtt EventRule.Arn
      Queues:
        - !Ref ECSEventBridgeSQSQueue
  LambdaFunctionEventSourceMapping:
    Type: AWS::Lambda::EventSourceMapping
    Properties:
      BatchSize: 20
      MaximumBatchingWindowInSeconds: 20
      Enabled: true
      EventSourceArn: !GetAtt ECSEventBridgeSQSQueue.Arn
      FunctionName: !GetAtt ECSEventBridgeECSAgentMonitorFunction.Arn
  SNSMonitoringTopic:
    Type: AWS::SNS::Topic
    Properties:
      Subscription:
        - Endpoint: !Ref NotificationEmail
          Protocol: email
      TopicName: !Sub ${AWS::StackName}-ECSAgentMonitoringTopic
      KmsMasterKeyId: !If
        - EncryptionCondition
        - !Ref KMSCMKKey
        - !Ref AWS::NoValue

Outputs:
  CWLogsInsightsDocs:
    Description: Link to Log Insights Analysis in CloudWatch
    Value: https://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/CWL_QuerySyntax.html
  CWLogsLink:
    Description: Link to the solution logs in CloudWatch
    Value: !Sub https://${AWS::Region}.console.aws.amazon.com/cloudwatch/home?region=${AWS::Region}#logsV2:log-groups/log-group/$252Faws$252Flambda$252F${ECSEventBridgeECSAgentMonitorFunction}
  CWMetricsLink:
    Description: Link to the solution CloudWatch metrics
    Value: !Sub https://${AWS::Region}.console.aws.amazon.com/cloudwatch/home?region=${AWS::Region}#metricsV2:graph=~(view~'timeSeries~stacked~false~region~'eu-west-1);namespace=~'ECS*2fECSAgentFailures