AWS Step Function
If your project or product follows a sequence of workflows, such as creating a order, payment of an order, and notifying a user about the order, then Step Function works great for you. Here is an example: When order is placed, there will be sequence - Customer login validation -> Order validation -> payment validation -> Order placed -> Notify user. Each workflow (Oorder validation, payment validation, etc) can be written in Lambda/EC2 and using Step Functions we shall direct a flow and integrate all AWS services to follow a process. Step functions also provides buit-in retry mechanism. If any workflow failes, you don't have to start the workflow from the beginning; instead configure retry mechanism to retry in a specific workflow.
Demo: Lets create a Step Function with a Lambda function. Lets make is very simple: an order is placed; this order needs to be validated. If order is available, then we shall success else we will return a failure message. This is just for demo purpose and I keep it super simple. In real-world project, we will be using multiple AWS services and workflows are usually complex.
a. Firstly, lets create two Lamda functions: ProcessSuccess and ProcessFailure. For creating the Lambda functions, navigate to Lambda services in AWS console.
c. Enter the function code as below:
import json
import boto3
print('Loading Sucess Lambda')
def lambda_handler(event, context):
# TODO implement
print('Message Received:')
print(event)
return {
'statusCode': 200,
'body': json.dumps('Hello from Success Lambda!')
}
d. Click on 'Deploy'. Similarly, create one more Lambda function - ProcessFailure. Note down the URL of bother the Lambda function: arn:aws:lambda:us-east-1:266290373221:function:FailureLambda and arn:aws:lambda:us-east-1:266290373221:function:ProcessSuccess
e. Lambda functions are created. Let us create a Step Function. Navigate to Step Function from the AWS console. The first time, you would see the below screen.
f. Navigate to 'State machines'. Click on 'Create State machine'.
g. Enter the below code. The code is in ASL format. Click 'Next'.
{
"Comment": "A simple AWS Step Functions state machine that automates a call center support session.",
"StartAt": "ProcessTransaction",
"States": {
"ProcessTransaction": {
"Type": "Choice",
"Choices": [
{
"Variable": "$.TransactionType",
"StringEquals": "Success",
"Next": "ProcessSuccess"
},
{
"Variable": "$.TransactionType",
"StringEquals": "Failure",
"Next": "ProcessFailure"
}
]
},
"ProcessSuccess": {
"Type": "Task",
"Resource": "arn:aws:lambda:us-east-1:266290373221:function:SuccessLambda",
"End": true
},
"ProcessFailure": {
"Type": "Task",
"Resource": "arn:aws:lambda:us-east-1:266290373221:function:FailureLambda",
"End": true
}
}
}
h. We need to create a new IAM role. To create a role, navigate to IAM console.
i. Click on 'Role' and 'Create Role'. Select 'Step Functions'. Click 'Next: Permissions'.
k. Click 'Next: Tags' and 'Next: Create Role'. Provide a name to the Step function role. Click 'Create Role'.
l. Role is created. Now, go back to the Step Function console. Provide the role that you just created. Click 'Create State Machine'.
m. Step function is ready! Now click on 'Start execution'.
o. Enter the below input value. Click 'Start Execution'.
{
"TransactionType": "Success"
}
The diagram shows the flow:
p. Again, Enter the below input value. Click 'Start Execution'.
{
"TransactionType": "Failure"
}
