Pass custom variables as an input to AWS step function - amazon-web-services

Question

Is thegre anyway for me to pass custom variables as an input to AWS step function ?
processData:
name: ingest-data
StartAt: Execute
States:
Execute:
Type: Task
Resource: "arn:aws:lambda:#{AWS::Region}:#{AWS::AccountId}:function:#{AWS::StackName}-ingestIntnlData"
Next: Check
Check:
Type: Choice
Choices:
- Variable: "$.results['finished']"
BooleanEquals: false
Next: Wait
- Variable: "$.results['finished']"
BooleanEquals: true
Next: Notify
Wait:
Type: Wait
SecondsPath: "$.waitInSeconds"
Next: Execute
Notify:
Type: Task
Resource: "arn:aws:lambda:#{AWS::Region}:#{AWS::AccountId}:function:#{AWS::StackName}-sendEMail"
End: true
I have two different stepfunctions which call the same lambda. I'm looking to pass a custom variable to the lambda to differentiate the calls made from the two step functions.
Something like a flag variable or if even there is a way to find out the name of the function which is invoking the lambda, that should also suffice.
Please help me out

Answer 1

We can build an object in Pass state and pass as input to lambda
"Payload.$":"$" simply passes through all the input
{
"StartAt":"Dummy Step 1 Output",
"States":{
"Dummy Step 1 Output":{
"Type":"Pass",
"Result":{
"name":"xyz",
"testNumber":1
},
"ResultPath":"$.inputForMap",
"Next":"invoke-lambda"
},
"invoke-lambda":{
"End":true,
"Retry":[
{
"ErrorEquals":[
"Lambda.ServiceException",
"Lambda.AWSLambdaException",
"Lambda.SdkClientException"
],
"IntervalSeconds":2,
"MaxAttempts":6,
"BackoffRate":2
}
],
"Type":"Task",
"Resource":"arn:aws:states:::lambda:invoke",
"Parameters":{
"FunctionName":"arn:aws:lambda:us-east-1:111122223333:function:my-lambda",
"Payload.$":"$"
}
}
}
}

Answer 2

You can use the context object and pass the ExecutionId like
{
"Comment": "A Catch example of the Amazon States Language using an AWS Lambda Function",
"StartAt": "nextstep",
"States": {
"nextstep": {
"Type": "Task",
"Resource": "arn:aws:lambda:eu-central-1:1234567890:function:catcherror",
"Parameters": {
"executionId.$": "$$.Execution.Id"
},
"End": true
}
}
}
This give you
arn:aws:states:us-east-1:123456789012:execution:stateMachineName:executionName
As you can see it contains your state machine name.
You can take decisions on them

Answer 3

You can create Lambda functions to use as steps within an workflow created by using AWS Step Functions. For your first step (the Lambda function you use as the first step), you can pass values to it to meet your needs:
https://www.c-sharpcorner.com/article/passing-data-to-aws-lambda-function-and-invoking-it-using-aws-cli/
Then you can pass data between steps using Lambda functions as discussed here:
https://medium.com/#tturnbull/passing-data-between-lambdas-with-aws-step-functions-6f8d45f717c3
You can create Lambda functions in other supported programming languages as well such as Java, as discussed here:
https://github.com/awsdocs/aws-doc-sdk-examples/tree/master/javav2/usecases/creating_workflows_stepfunctions
AS you can see, there is a lot of development options when using Lambda and AWS Step Functions.