Cost monitor Lambda

This module builds the infrastructure required to run a Lambda Function to retrieve the current AWS cost and the end of month forecasted cost. The function can be configured to report it's finding regularly (scheduled mode) or only if certain threshold is exceeded (alerts only mode). In both cases it uses an Slack webhook to send ots findings. Use the input parameter alerts_only to define this behaviour.

Before Running Terraform

1. Before instantiating the module, follow these instructions to create an slack webhook
2. Create a customer manager KMS key. Make sure the account Terraform will use to create the infrastructure can use it.
3. Encript the slack webhook URL

echo -n 'slack webhook URL' > plaintext-file

aws kms encrypt --key-id <id of CMK created in step 2> --plaintext fileb://plaintext-file --output text --query CiphertextBlob

4. Use the output of this command as a value for encripted_slack_webhook_url. The module will decript it, and store it as a secret in AWS Secrets Manager
5. Run /lambda/build.py.
6. Fill the rest of the module input parameters and run Terraform plan/apply

Requirements

Name	Version
aws	4.60.0

Providers

Name	Version
aws	4.60.0

Modules

No modules.

Resources

Name	Type
aws_cloudwatch_event_rule.lambda_trigger	resource
aws_cloudwatch_event_target.event_target	resource
aws_iam_role.iam_for_lambda	resource
aws_lambda_function.cost_alert	resource
aws_lambda_permission.allow_events_bridge_to_run_lambda	resource
aws_secretsmanager_secret.secret	resource
aws_secretsmanager_secret_version.secret_version	resource
aws_iam_policy_document.assume_role	data source
aws_iam_policy_document.inline_policy	data source
aws_kms_secrets.secret_value	data source

Inputs

Name	Description	Type	Default	Required
alert_threshold	Integer representing the % above which alerts will be sent to slack	number	n/a	yes
alerts_only	The lambda will only post messages if a threshold is exceeded (alerts only mode). If set to false (a.k.a. scheduled mode) messages will be sent regularly	bool	true	no
encripted_slack_webhook_url	Encript the webhook URL with KMS, and use it in this variable. See readme.md	string	n/a	yes
frequency	Frequency to run the lambda (cron formating is also accepted)	string	"rate(1 day)"	no
image_uri	URI of the repo where the lambda image is stored	string	n/a	yes
name	Name prefix to be applied to all resources	string	"cost_alert"	no

Outputs

Name	Description
lambda_arn	Lambda function ARN