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AWS Resources

You will need:

A lambda function
An SNS topic that the lambda function is subscribed to
A CloudWatch alarm that sends breach and OK events to your SNS topic

CloudWatch

Sample Breach Event

Note: This is the EventRecord.Records[0].SNS.Message content

{
    "AlarmName": "test-cw-go-mem",
    "AlarmDescription": null,
    "AWSAccountId": "123456789",
    "NewStateValue": "ALARM",
    "NewStateReason": "Threshold Crossed: 2 out of the last 2 datapoints [14.0 (12/03/20 14:31:00), 14.0 (12/03/20 14:26:00)] were greater than the threshold (10.0) (minimum 2 datapoints for OK -> ALARM transition).",
    "StateChangeTime": "2020-03-12T14:36:48.821+0000",
    "Region": "US East (Ohio)",
    "OldStateValue": "INSUFFICIENT_DATA",
    "Trigger": {
        "MetricName": "MemoryUtilized",
        "Namespace": "ECS/ContainerInsights",
        "StatisticType": "Statistic",
        "Statistic": "AVERAGE",
        "Unit": null,
        "Dimensions": [
            {
                "value": "dev-twoheavy-svc",
                "name": "ServiceName"
            },
            {
                "value": "dev-twoheavy",
                "name": "ClusterName"
            }
        ],
        "Period": 300,
        "EvaluationPeriods": 2,
        "ComparisonOperator": "GreaterThanThreshold",
        "Threshold": 10,
        "TreatMissingData": "- TreatMissingData:                    missing",
        "EvaluateLowSampleCountPercentile": ""
    }
}

Sample Recovery Event

{
    "AlarmName": "test-cw-go-mem",
    "AlarmDescription": null,
    "AWSAccountId": "123456789",
    "NewStateValue": "OK",
    "NewStateReason": "Threshold Crossed: 2 out of the last 2 datapoints [14.0 (12/03/20 14:45:00), 14.0 (12/03/20 14:40:00)] were not greater than the threshold (20.0) (minimum 1 datapoint for ALARM -> OK transition).",
    "StateChangeTime": "2020-03-12T14:50:13.507+0000",
    "Region": "US East (Ohio)",
    "OldStateValue": "ALARM",
    "Trigger": {
        "MetricName": "MemoryUtilized",
        "Namespace": "ECS/ContainerInsights",
        "StatisticType": "Statistic",
        "Statistic": "AVERAGE",
        "Unit": null,
        "Dimensions": [
            {
                "value": "dev-twoheavy-svc",
                "name": "ServiceName"
            },
            {
                "value": "dev-twoheavy",
                "name": "ClusterName"
            }
        ],
        "Period": 300,
        "EvaluationPeriods": 2,
        "ComparisonOperator": "GreaterThanThreshold",
        "Threshold": 20,
        "TreatMissingData": "- TreatMissingData:                    missing",
        "EvaluateLowSampleCountPercentile": ""
    }
}

Lambda

The Lambda handler will be main

ENV Vars

SLACK_CHANNEL
SLACK_ICON
SLACK_USERNAME
SLACK_WEBHOOK

Using

You can retrieve this from https://bhi-oss.s3.us-east-2.amazonaws.com/cw-go-slack/latest.zip

SNS Access Policy Example

{
  "Version": "2008-10-17",
  "Id": "__default_policy_ID",
  "Statement": [
    {
      "Sid": "CloudWatchPublish",
      "Effect": "Allow",
      "Principal": {
        "Service": "cloudwatch.amazonaws.com"
      },
      "Action": "SNS:Publish",
      "Resource": "arn:aws:sns:REGION:ACCOUNT_ID:TOPIC_NAME"
    }
  ]
}

Terraform

You can find sample Terraform code to stand up a function and an SNS topic in the terraform/ directory

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