Cross Lambda Invocation between AWS Lambda

!cross-lambda-invocation.md

How to perfrom Cross Invocations between Lambda Functions

• Create a Lambda function, which will receive the lambda invocation, choose python 3.7 or upper as your runtime, you can use the AWS default role or choose your predefined role and lastly copy the sample function (child_lambda.py) below.
• Copy the function's ARN then head over to AWS IAM service and navigate to policies
• Click on Create policy
• Click the JSON icon, copy and paste the policy.json below
• Replace the "Resource" value in the policy.json with the ARN of the Lambda function
• Click on Review policy and give a name and description to your policy and then create policy
• Head over to IAM and click on Roles, create a new role, click on Lambda as the AWS service then click on Permissions and tick the AWSLambdaBasicExecutionRole and also tick the new policy role you just created and lastly click on Tags
• Give the new role you created a name and description.
• Head over to AWS Lambda and create a new lambda which will send the invocations to the function you've created previously. Select your prefered runtime and choose the role you created in the step above.
• You can copy the code in the parent_lambda.py and add your enviromental variable(AWS account id, function name and region) in the lambda function.
• And if you run the function you'll see the child function will be invoked and also the response of the function you just invoked in the parent's function.

**Note: This can only happen across regions**

child_lambda.py

import json

def lambda_handler(event, context):
    #Collect data sent by the parent lambda
    amount = event['Amount']
    quantity  = event['Quantity']
 
    #Implement Logic Here
    result = int(amount) * int(quantity)
 
    #return the result
    return result

parent_lambda.py

import json
import boto3
 
# Define the client to interact with AWS Lambda
client = boto3.client('lambda')

#Get the credentials from environmental variables
adw_accout_id = os.environ['AccountId']
adw_function_name = os.environ['FunctionName']
region_name = os.environ['Region']


def lambda_handler(event,context):
 
    #Define the payload that will be passed to the child function
    payload = {"Amount": "1000",
               "Quantity": "2"}
    
    #Invoke Child's Function with payload
    response = client.invoke(
            FunctionName = f'arn:aws:lambda:{region_name}:{adw_accout_id}:function:{adw_function_name}', #Child's ARN
            InvocationType = 'RequestResponse',
            Payload = json.dumps(payload)
                )
    
    #After child's execution has been executed you can get the child's response of the lambda
    responseFromChild = json.load(response['Payload'])
    
    return responseFromChild

policy.json

{
    "Version":"2012-10-17",
    "Statement":[
       {
          "Sid":"VisualEditor0",
          "Effect":"Allow",
          "Action":[
             "lambda:InvokeFunction",
             "lambda:InvokeAsync"
          ],
          "Resource":"ARN-of-lambda-you-want-to-invoke"
       }
    ]
 }