---
AWSTemplateFormatVersion: '2010-09-09'
Description: >

  This Cloudformation Template deploys the Redis Cluster (Amazon ElastiCache) used by the Scalelite load balancer.

  Disclaimer: Not for production use. Demo and testing purposes only.

  Author: David Surey <suredavi@amazon.com>

Parameters:
  BBBNotificationTopic:
    Description: Topic to be used for alarm notifications
    Type: String
  BBBCACHEDBInstanceType:
    Description: Instance type for Amazon ElastiCache (Redis)
    Type: String
    Default: cache.t3.micro
  BBBPrivateDBSubnets:
    Description: Comma separated list of the private database subnets
    Type: CommaDelimitedList
  BBBCACHEDBSecurityGroup:
    Description: Security Group that should be assigned for cache database
    Type: String
  BBBCacheAZMode:
    Description: Redis Cache AZ Mode
    Type: String
    Default: single-az
    AllowedValues:
      - single-az
      - cross-az

Resources:
  BBBCacheSubnetGroup:
    Type: AWS::ElastiCache::SubnetGroup
    Properties:
      Description: !Sub CacheSubnetGroup-${AWS::StackName}
      SubnetIds: !Ref BBBPrivateDBSubnets

  BBBParametersGroup:
    Type: AWS::ElastiCache::ParameterGroup
    Properties:
      CacheParameterGroupFamily: "redis7"
      Description: "Modifications to support better performance"
      Properties:
        tcp-keepalive: 60
        timeout: 900

  BBBElasticacheRedis:
    Type: AWS::ElastiCache::CacheCluster
    Properties:
      NumCacheNodes: 1
      CacheNodeType:
        Ref: BBBCACHEDBInstanceType
      CacheParameterGroupName:
        Ref: BBBParametersGroup
      CacheSubnetGroupName: !Ref BBBCacheSubnetGroup
      AZMode: !Ref BBBCacheAZMode
      Engine: "redis"
      EngineVersion: "7.0"
      NotificationTopicArn: !Ref BBBNotificationTopic
      VpcSecurityGroupIds:
        - Ref: BBBCACHEDBSecurityGroup

  BBBDatabaseACPUUtilizationTooHighAlarm:
    Type: 'AWS::CloudWatch::Alarm'
    Properties:
      AlarmActions:
        - Ref: BBBNotificationTopic
      AlarmDescription: 'Average Cache-Node CPU utilization over last 10 minutes too high.'
      ComparisonOperator: GreaterThanThreshold
      Dimensions:
        - Name: CacheClusterId
          Value:
            Ref: BBBElasticacheRedis
        - Name: CacheNodeId
          Value: 0001
      EvaluationPeriods: 1
      MetricName: CPUUtilization
      Namespace: 'AWS/ElastiCache'
      OKActions:
        - Ref: BBBNotificationTopic
      Period: 600
      Statistic: Average
      Threshold: 80

  BBBCacheACPUCreditBalanceTooLowAlarm:
    Type: 'AWS::CloudWatch::Alarm'
    Properties:
      AlarmActions:
        - Ref: BBBNotificationTopic
      AlarmDescription: 'Average Cache-Node CPU credit balance over last 10 minutes too low, expect a significant performance drop soon.'
      ComparisonOperator: LessThanThreshold
      Dimensions:
        - Name: CacheClusterId
          Value:
            Ref: BBBElasticacheRedis
        - Name: CacheNodeId
          Value: 0001
      EvaluationPeriods: 1
      MetricName: CPUCreditBalance
      Namespace: 'AWS/ElastiCache'
      OKActions:
        - Ref: BBBNotificationTopic
      Period: 600
      Statistic: Average
      Threshold: 20

  BBBCacheAFreeableMemoryTooLowAlarm:
    Type: 'AWS::CloudWatch::Alarm'
    Properties:
      AlarmActions:
        - Ref: BBBNotificationTopic
      AlarmDescription: 'Average Cache-Node freeable memory over last 10 minutes too low, performance may suffer.'
      ComparisonOperator: LessThanThreshold
      Dimensions:
        - Name: CacheClusterId
          Value:
            Ref: BBBElasticacheRedis
        - Name: CacheNodeId
          Value: 0001
      EvaluationPeriods: 1
      MetricName: FreeableMemory
      Namespace: 'AWS/ElastiCache'
      OKActions:
        - Ref: BBBNotificationTopic
      Period: 600
      Statistic: Average
      Threshold: 64000000 

Outputs:
  BBBCacheDBAddress:
    Description: The Big Blue Button Cache Database Address
    Value:
      Fn::GetAtt:
        - BBBElasticacheRedis
        - RedisEndpoint.Address
  BBBCacheDBPort:
    Description: The Big Blue Button Cache Database Port
    Value:
      Fn::GetAtt:
        - BBBElasticacheRedis
        - RedisEndpoint.Port
  BBBElasticacheRedis: 
    Description: The Big Blue Button Cache Redis Cluster
    Value:
      Ref: BBBElasticacheRedis
  BBBParametersGroup: 
    Description: The Big Blue Button Cache Redis Parameter Group
    Value:
      Ref: BBBParametersGroup
  BBBCacheSubnetGroup: 
    Description: The Big Blue Button Cache Redis Subnet Group
    Value:
      Ref: BBBCacheSubnetGroup