When I googled the precedent cases, there were many examples of Python, so the minimum setting memo when I did it by hand with [Ruby] doc.

1. Create AWS Lambda with runtime Ruby

Create with a button click from the Lambda console screen on the Web

--Runtime with Ruby 2.7 --Give ce: GetCostAndUsage to the execution role -[Cost Explorer permissions will appear if you enable them as root] ce_auth should be

2. Write the acquisition process in Ruby

`lambda_functions.rb`


require 'aws-sdk'
require 'net/http'
require 'uri'
require 'json'

#Lambda entry point
def lambda_handler(event:, context:)
  fetch_cost
    .then { |response| pretty_response(response) }
    .then { |message| notify_slack(message) }

  #Return as HTTP response
  { statusCode: 200, body: 'ok' }
end

#Get billing information
def fetch_cost(time = Time.now)
  #I have already authenticated, so I don't need credentials(See below)
  client = Aws::CostExplorer::Client.new(region: 'us-east-1')

  client.get_cost_and_usage(
    time_period: {
      start: Time.local(time.year, time.month, 1).strftime('%F'),
      end: time.strftime('%F'),
    },
    granularity: 'MONTHLY',
    metrics: ['AmortizedCost'],
    group_by: [ { type: "DIMENSION",key: 'SERVICE' }]
  )
end

#Formatting API return values
def pretty_response(res)
  #abridgement. Appropriately
end

#Post to Slack
def notify_slack(message)
  #incoming Webhook Set the set URL in the environment variable
  uri = URI.parse(ENV['SLACK'])
  params = { text: message }
  http = Net::HTTP.new(uri.host, uri.port)
  http.use_ssl = true
  res = http.start do
    request = Net::HTTP::Post.new(uri.path)
    request.set_form_data(payload: params.to_json)
    http.request(request)
  end

  unless res.is_a? Net::HTTPSuccess
    raise 'Failed POST Slack'
  end

  res
end

Click here for the full source (gist). What you are doing is almost the same as [Getting process in Python of the precedent case of Developers.IO] [class method].

If you want to change what you want to see, you can change [what to pass to ʻAws :: CostExplorer :: Client # get_cost_and_usage] [api_doc] or change pretty_response`.

3. Set startup time in CloudWatch Events

"Add trigger" on the Lambda function setting screen
Select "Event Bridge (CloudWatch Events)"
Can be set in the same way as cron (Reference: [AWS_Cron expression wildcard] cron)

I was addicted to IAM certification

I didn't know where to get the IAM authentication when executing the Lambda function, but if I'm using the aws-sdk gem, I've done it without doing anything. The reason is as follows.

-[In the Lambda execution environment, the environment variables (ʻENV) are set to ʻAWS_ACCESS_KEY_ID and ʻAWS_SECRET_ACCESS_KEY`] ENV. -[aws-sdk gem reads the above environment variables without permission and authenticates] rdoc. ――So you don't have to do anything.

At first I didn't know this, so it was useless because I made an IAM separately from the role for execution and used that access key and path.

Referenced web page

--[I tried to notify Slack of the billing amount for each AWS service every day --Developers.IO] classmethod --Python example. It feels like I ported this to Ruby. -[Building Lambda Functions with Ruby-AWS Lambda Developer Guide] doc --Official Ruby documentation for AWS Lambda. --[Using AWS Lambda Environment Variables --AWS Lambda Developer Guide] ENV --About Lambda environment variables. Many are set from the beginning.

AWS SDK for Ruby - Version 3 API Document --The official API documentation for aws-sdk gem.
Aws::CostExplorer::Client#get_cost_and_usage API Document --The official API documentation for CostExplorer # get_cost_and_usage on aws-sdk. ――Depending on the argument, you can get various things such as daily billing amount. -[AWS_Cron expression wildcard] cron --I didn't know the AWS cron ?. --[Permission Management Overview --AWS Billing Information and Cost Management] ce_auth --Set CostExplorer to be touched by IAM role.

Notify Slack of AWS bills daily with Lambda for Ruby