slack-aws-sns

Create a slack webhook

Unfortunately this is a ui driven process

1. Go to https://your-company.slack.com/services/new
2. Click 'Incoming WebHooks'
3. Create a new one by selecting a channel and clicking "Add incoming webhook integration"
4. Copy the webhook url for use later

Create sns topic

> aws sns create-topic --name Billing
{
    "TopicArn": "arn:aws:sns:us-east-1:111122223333:Billing"
}
> aws sns subscribe --topic-arn arn:aws:sns:us-east-1:111122223333:Billing --protocol email --notification-endpoint <your-email-address>

Create cloudwatch alarm

> aws cloudwatch put-metric-alarm \
	--alarm-name "billing more than $1" \
	--comparison-operator GreaterThanOrEqualToThreshold \
	--evaluation-periods 1 \
	--metric-name EstimatedCharges \
	--namespace AWS/Billing \
	--dimensions Name=Currency,Value=USD" \
	--period 21600 \
	--statistic Maximum \
	--threshold 1 \
	--actions-enabled \
	--alarm-actions arn:aws:sns:us-east-1:111122223333:Billing

Create the aws lambda function

> aws lambda create-function \
	--function-name snsToSlack \
	--zip-file file://file-path/snsToSlack-created-from-snsToSlack.js.zip \
	--role role-arn-looked-up-from-iam \
	--handler index.handler \
	--runtime nodejs
{
    "CodeSize": number,
    "Description": "string",
    "FunctionArn": "string",
    "FunctionName": "string",
    "Handler": "string",
    "LastModified": "string",
    "MemorySize": number,
    "Role": "string",
    "Runtime": "string",
    "Timeout": number
}

Subscribe to lambda function to the sns topic

> aws sns subscribe \
    --topic-arn arn:aws:sns:us-east-1:111122223333:Billing \
    --protocol lambda \
    --notification-endpoint arn:aws:lambda:REGION:ACCOUNT:function:LAMBDAFUNCTION

Concept heavily borrowed from

https://medium.com/cohealo-engineering/how-set-up-a-slack-channel-to-be-an-aws-sns-subscriber-63b4d57ad3ea