Introduction
In the previous post, Daily Automated AWS Cost Reports by Email – Part 3, we created a Lambda function that queries the current AWS account cost using the Cost Explorer API and sends the result via SNS to an email address. Now, in this final step, we’ll schedule this Lambda function to run automatically every day at 8 PM using Amazon EventBridge.
Let’s dive into how to add the scheduled trigger to your AWS SAM template to fully automate your daily AWS cost report emails.
Resources
- GitHub: DevOpsBug/AWS_DailyCostReport (Branch: “event_bridge_trigger”).
Architecture
First let’s remember the Architecture from the previous tutorials. The solution uses a scheduled EventBridge rule to invoke a Lambda function once per day. This function queries the AWS Cost Explorer API to retrieve the latest month-to-date cost data, grouped by service. The resulting cost report is then published to an SNS topic with Email subscription. In this tutorial we will add the EventBridge Trigger to invoke the Lambda Function once per day.
Prerequisites
Before we begin, ensure you have the following:
- AWS Account: Active account with appropriate permissions.
- AWS CLI: Installed and configured with your credentials.
- SAM CLI: Installed and configured on your local machine.
- AWS SDK for Python (Boto3): Installed in your development environment.
Step 1: Add an EventBridge Schedule to Your SAM Template
Adding a scheduled EventBridge Trigger to a Lambda Function is very easy using AWS SAM. All you need to do is to add the following section to the existing Lambda Function Resource in the SAM Template:
Events:
DailySchedule:
Type: Schedule
Properties:
Schedule: cron(0 20 * * ? *)
Now let’s incorporate this into our previously defined SAM Template. Modify your template.yaml to include a scheduled event source for your Lambda function. Here’s how the final SAM Template should look with the EventBridge rule added:
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: >
AWS_DailyCostReport
Sample SAM Template for AWS_DailyCostReport
Globals:
Function:
Timeout: 3
MemorySize: 128
Parameters:
EmailAddress:
NoEcho: true
Description: E-Mail Address for SNS Subscription
Type: String
Resources:
CostReportSNSTopic:
Type: AWS::SNS::Topic
Properties:
TopicName: DailyCostReport
Subscription:
- Endpoint: !Ref EmailAddress
Protocol: email
CostReportFunction:
Type: AWS::Serverless::Function
Properties:
FunctionName: CostReportFunction
CodeUri: lambda/
Handler: app.lambda_handler
Runtime: python3.9
Architectures:
- x86_64
Policies:
- Statement:
- Effect: Allow
Action:
- ce:GetCostAndUsage
Resource: "*"
- SNSPublishMessagePolicy:
TopicName: !GetAtt CostReportSNSTopic.TopicName
Environment:
Variables:
SNS_TOPIC_ARN: !Ref CostReportSNSTopic
Events:
DailySchedule:
Type: Schedule
Properties:
Schedule: cron(0 19 * * ? *)
Outputs:
CostReportFunction:
Description: "Cost Report Lambda Function ARN"
Value: !GetAtt CostReportFunction.Arn
CostReportFunctionIamRole:
Description: "Implicit IAM Role created for Cost Report function"
Value: !GetAtt CostReportFunctionRole.Arn
The Schedule expression cron(0 19 * * ? *) corresponds to 7 PM UTC (8 PM CET) every day.
Step 2: Deploy the Updated Template
Run the following SAM CLI commands to redeploy the stack:
sam build
sam deploy
The SAM CLI will now deploy the changeset and it will look something like this:
Initiating deployment
=====================
Uploading to AWS-DailyCostReport/123456789012345667.template 1789 / 1789 (100.00%)
Waiting for changeset to be created..
CloudFormation stack changeset
-------------------------------------------------------------------------------------------------
Operation LogicalResourceId ResourceType Replacement
-------------------------------------------------------------------------------------------------
+ Add CostReportFunctionDail AWS::Lambda::Permissio N/A
ySchedulePermission n
+ Add CostReportFunctionDail AWS::Events::Rule N/A
ySchedule
* Modify CostReportFunction AWS::Lambda::Function False
-------------------------------------------------------------------------------------------------
Changeset created successfully. arn:aws:cloudformation:us-east-1:123456789:changeSet/samcli-deploy1234567890123456-123456789-123456789123456
Previewing CloudFormation changeset before deployment
======================================================
Deploy this changeset? [y/N]: y
2025-05-29 13:57:25 - Waiting for stack create/update to complete
CloudFormation events from stack operations (refresh every 5.0 seconds)
-------------------------------------------------------------------------------------------------
ResourceStatus ResourceType LogicalResourceId ResourceStatusReason
-------------------------------------------------------------------------------------------------
UPDATE_IN_PROGRESS AWS::CloudFormation::S AWS-DailyCostReport User Initiated
tack
UPDATE_IN_PROGRESS AWS::Lambda::Function CostReportFunction -
UPDATE_COMPLETE AWS::Lambda::Function CostReportFunction -
CREATE_IN_PROGRESS AWS::Events::Rule CostReportFunctionDail -
ySchedule
CREATE_IN_PROGRESS AWS::Events::Rule CostReportFunctionDail Resource creation
ySchedule Initiated
CREATE_COMPLETE AWS::Events::Rule CostReportFunctionDail -
ySchedule
CREATE_IN_PROGRESS AWS::Lambda::Permissio CostReportFunctionDail -
n ySchedulePermission
CREATE_IN_PROGRESS AWS::Lambda::Permissio CostReportFunctionDail Resource creation
n ySchedulePermission Initiated
CREATE_COMPLETE AWS::Lambda::Permissio CostReportFunctionDail -
n ySchedulePermission
UPDATE_COMPLETE_CLEANU AWS::CloudFormation::S AWS-DailyCostReport -
P_IN_PROGRESS tack
UPDATE_COMPLETE AWS::CloudFormation::S AWS-DailyCostReport -
tack
-------------------------------------------------------------------------------------------------
CloudFormation outputs from deployed stack
-------------------------------------------------------------------------------------------------
Outputs
-------------------------------------------------------------------------------------------------
Key CostReportFunctionIamRole
Description Implicit IAM Role created for Cost Report function
Value arn:aws:iam::1234567890123:role/AWS-DailyCostReport-
CostReportFunctionRole-123456789
Key CostReportFunction
Description Cost Report Lambda Function ARN
Value arn:aws:lambda:us-east-1:1234567890:function:CostReportFunction
-------------------------------------------------------------------------------------------------
Successfully created/updated stack - AWS-DailyCostReport in us-east-1
If it looks like this, the stack was deployed successfully.
Verify Changes
To verify the changes you can go the Web Console and check if the EventBridge Rule was created. To do this, navigate to the EventBridge Service, navigate to “Rules” find the newly created rule AWS-DailyCostReport-CostReportFunctionDailySchedule-xxxxxxxxxx and click on it. In that rule you can explore the Event Schedule and Targets tabs to verify that the EventBridge rule has been created correctly. It looks something like this:
You should also receive an E-Mail on the specified E-Mail Address at the time specified in the schedule.
Conclusion
In this final post of the series, you learned how to use Amazon EventBridge to schedule your Lambda function to run automatically each day. With this in place, your cost reporting pipeline is now fully automated — from querying the AWS Cost Explorer API, to sending a cost summary via email, all without manual intervention.
This completes the Daily Automated AWS Cost Reports by Email series:
- Part 1: Developing and Testing Lambda Functions Locally
- Part 2: Querying Cost Explorer for Daily Cost Reports
- Part 3: Sending Cost Reports via Email with SNS
- Part 4: Scheduling with EventBridge
You can find the complete source code in the GitHub repository.
Thanks for following along! If you have questions or feedback, feel free to reach out or open an issue in the repo.
COMING UP NEXT - Learn how to manage multiple Kubernetes cluster configs cleanly using KUBECONFIG, improve CLI safety by showing your current context in the prompt, and enable autocompletion to boost productivity.
🙂 Happy coding!