# EventBridge Schedule to Step Functions - No-Code/No-Lambda **Use Case:-** We have a business use case where we need to call our nightly job for multiple tenants. Initially, I planned to use EventBridge Bus and Rules to achieve this goal. However, we discovered that EventBridge Rules has a limit of 5 targets, which would prevent us from adding more tenants as input for the nightly job. I want to avoid maintaining multiple rules for the same use case, so I came up with this solution. I believe No-Code/Less-Code approach using AWS Step Functions and EventBridge is the best way forward for our development needs. **The Architecture:**\- ![EventBridge Scheduler](https://cdn.hashnode.com/res/hashnode/image/upload/v1678739172899/6d763800-3e46-4bb5-b1ba-01e166e0f864.png align="center") ![]( align="center") ![State Machine](https://cdn.hashnode.com/res/hashnode/image/upload/v1678739233981/18ee6d0b-5e2b-4238-a81f-1a2518bf60dd.png align="center") ![]( align="center") **Steps**:- 1. Configure EventBridge Schduler. You can read my prior 2 posts [here](https://awsmantra.com/eventbridge-scheduler-startstop-ecs-instance) and [here](https://awsmantra.com/eventbridge-scheduler-startstop-ec2-instance). 2. Populate DynamDB static data. 3. Create a Step Function State Machine using AWS ASL language. You can download the source code from [here](https://github.com/awsmantra/eventbridge-schedules-to-stepfunction), which has been implemented using **AWS CDK** and **SAM**, whichever approach you prefer. **CDK Deploy:-** ```json 1) cd cdk 2) npm install 3) cdk deploy --all -a "npx ts-node bin/app.ts" --profile ``` **SAM Deploy:-** ```json 1) cd sam 2) sam deploy --stack-name LegacyAppStack --capabilities CAPABILITY_NAMED_IAM --guided --profile ``` **Populate Static Data in DynamoDB:-** ```json 1) cd dynamodb 2) ./dynamodb.sh ``` You will see the below records in the DynamoDB table. ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1679176653843/347be37f-1597-451d-8e5a-72188fc16659.png align="center") **Understand State Machine:-** AWS step functions are integrated with more than 200+ AWS services and you can call 9K+ API from step functions. There are 2 ways you can integrate step functions with other services, either using [AWS SDK Integration](https://docs.aws.amazon.com/step-functions/latest/dg/supported-services-awssdk.html) or you can use [Optimized integration](https://docs.aws.amazon.com/step-functions/latest/dg/connect-supported-services.html). In this example, I am using [Default Response](https://docs.aws.amazon.com/step-functions/latest/dg/connect-to-resource.html#connect-default) (Request/Response) optimized integration pattern with Express workflow. ```json "GetTenantList": { "Type": "Task", "Resource": "arn:aws:states:::dynamodb:getItem", "Parameters": { "TableName": "LegacyApp", "Key": { "PK": { "S": "METADATA" }, "SK": { "S": "METADATA" } } }, "ResultPath": "$.context", "OutputPath": "$.context.Item.TenantList.L", "Next": "IterateTenantList" } ``` I am utilizing "arn:aws:states:::dynamodb:getItem" API to retrieve data from DynamoDB by passing the primary key (PK) and sort key (SK). Step functions offer access to all [CRUD](https://docs.aws.amazon.com/step-functions/latest/dg/connect-ddb.html) API operations available with DynamoDB. After filtering output with the ResultPath and OutputPath, the output of the aforementioned operation would be as follows. ```json [ { "S": "TENANT#123456" }, { "S": "TENANT#456789" } ] ``` Now I am iterating TenantList using Map. The Map states concurrently iterate over a collection of items in a dataset, such as a list of S3 Objects, CSV file or JSON object. it repeats a set of steps for each item in the collection. ```json "Type": "Map", "ItemProcessor": { "ProcessorConfig": { "Mode": "INLINE" } ``` The Map states have an "**Inline**" mode where they can only accept input in the form of a JSON array. When operating in this mode, the map states can handle up to 40 concurrent iterations. However, the Map states also offer a "**Distributed**" mode that can support up to 10,000 parallel child workflows. I am planning to write a blog about these features soon. Next, I am getting messages from DynamoDB and transforming them before sending them to SNS. ```json "StartAt": "GetTenant", "States": { "GetTenant": { "Type": "Task", "Resource": "arn:aws:states:::dynamodb:getItem", "Parameters": { "TableName": "LegacyApp", "Key": { "PK": { "S.$": "$" }, "SK": { "S.$": "$" } } }, "InputPath": "$.S", "Next": "TransformMessage", "ResultSelector": { "message.$": "States.StringToJson($.Item.Message.S)" } }, "TransformMessage": { "Type": "Pass", "Parameters": { "version.$": "$.message.version", "source.$": "$.message.source", "eventType.$": "$.message.eventType", "details": { "tenantId.$": "$.message.details.tenantId" }, "correlationId.$": "States.UUID()" }, "Next": "SendMessageToLegacyApp" } ``` Step functions provide several [**intrinsic**](https://docs.aws.amazon.com/step-functions/latest/dg/amazon-states-language-intrinsic-functions.html) functions. You can see here I am using "States.StringToJson" and "States.UUID". Intrinsic functions will help you to perform basic data processing operations without using a Task state. Here is the output of the above 2 tasks. ```json { "details": { "tenantId": 123456 }, "correlationId": "f43e0b5b-c187-483f-800e-44fb71486494", "source": "SampleApp", "eventType": "LegacyApp", "version": "1.0" } ``` In the last step, I am sending messages to the SNS topic using the following code. ```json "SendMessageToLegacyApp": { "Type": "Task", "Resource": "arn:aws:states:::sns:publish", "Parameters": { "Message.$": "$", "TopicArn": "${LegacyAppSNSPath}" }, "End": true } ``` **Cleanup:-** ```json sam delete --stack-name LegacyAppStack --profile OR cdk destroy --profile ``` **Wrap-Up:-** We have not utilized any Lambda code in our implementation, relying entirely on AWS API integration. I believe that each line of code in any service is a liability, it carries a certain amount of risk, and it requires ongoing maintenance, monitoring, and the creation of unit/integration test cases. Let me know if you have any better way to solve this use case. > Code is more art to me. I don’t want computer art - Ben Pyle