How to run EC2 instance with Step Function

Question

How can I run an instance using Step function? The best if it can by run sync way with outputting instance ID :)

Accepted Answer

You can use Step Functions [AWS SDK Service Integrations](https://docs.aws.amazon.com/step-functions/latest/dg/supported-services-awssdk.html) to call the EC2 API directly. Below is Amazon States Language for a simple example (you would need to update the specified security group and you need to ensure the Execution Role for your state machine has the necessary privs to make the call to the EC2 API).

An easy way to build this stuff up is to first go to the EC2 Console where you can build up the instance type you want, then use the Review Commands link to show the API parameters:
![Enter image description here](/media/postImages/original/IM1C5GsaWsRyyeMwujMVOHDw)

Then you can just paste those into the API Parameters for your Task State in Step Functions:
![Enter image description here](/media/postImages/original/IMYi9WFOZSRKKRK9-KcshEmA)

And if you want to do multiple steps, such as create a new security group or look up such info, you can do that in previous workflow steps and pass into your RunInstances call.

```
{
  "StartAt": "RunInstances",
  "States": {
    "RunInstances": {
      "Type": "Task",
      "End": true,
      "Parameters": {
        "MaxCount": 1,
        "MinCount": 1,
        "ImageId": "ami-0663b059c6536cac8",
        "InstanceType": "t2.micro",
        "EbsOptimized": false,
        "NetworkInterfaces": [
          {
            "AssociatePublicIpAddress": true,
            "DeviceIndex": 0,
            "Groups": [
              "sg-f8717ed8"
            ]
          }
        ],
        "MetadataOptions": {
          "HttpEndpoint": "enabled",
          "HttpPutResponseHopLimit": 2,
          "HttpTokens": "required"
        },
        "PrivateDnsNameOptions": {
          "HostnameType": "ip-name",
          "EnableResourceNameDnsARecord": true,
          "EnableResourceNameDnsAAAARecord": false
        }
      },
      "Resource": "arn:aws:states:::aws-sdk:ec2:runInstances"
    }
  }
}
```

Answer

Hi , 
There is multiple ways to we can run EC2 with step function.
1) invoke lambda from step function 
     in lambda, need to implement run the EC2 instance
2) invoke SSM from step function

Both ways we can run EC2 instance from step function

Try below code snippet to create instance in boto3

import json
import boto3
import os
import time

ec2_client = boto3.client("ec2", region_name=os.environ['AWS_REGION'])
 
def create_instance():
    instances = ec2_client.run_instances(
        ImageId=os.environ['ami'],
        MinCount=1,
        MaxCount=1,
        SecurityGroupIds=[os.environ['security_group']],
        InstanceType=os.environ['instance_type'],
        SubnetId=os.environ['subnet_id'],
        IamInstanceProfile={'Name': 'ec2-instance-role'}
        )
    instance_id = instances["Instances"][0]["InstanceId"]
   
    max_time = 800 # 10min
    start_time = 0
    health_check = False
   
    while start_time <= max_time:
        response = ec2_client.describe_instance_status(InstanceIds=[instance_id])
        for instance in response['InstanceStatuses']:
            print("EC2 System status:%s" %instance['SystemStatus']['Status'])
            if instance['SystemStatus']['Status'] == 'initializing':
                continue
            elif instance['SystemStatus']['Status'] == 'ok':
                health_check = True
 
                break
        print("Health Check:%s" %health_check)
        if health_check:
            break
        else:
            # wait for a min for next iteration
            time.sleep(60)
            start_time += 60 
            continue
   
    if not health_check:
        return {
            'statusCode': 400,
            'body': "The Instance %s health check failed" %instances["Instances"][0]["InstanceId"]
        }
   
    return instances["Instances"][0]["InstanceId"]

def lambda_handler(event, context):
   try:
        instanceId = create_instance()   
        return {
            'statusCode': 200,
            'body': json.dumps({'instance_id': instanceId})
        }
   except Exception as e:
        return {
            'statusCode': 400,
            'body': 'Creation of EC2 instance failed:%s' %e
        }
   
 By invoking above function before, need to add subnet, security role etc. which are defined in OS.

Answer

Hi,

You have a full example in this article: https://www.pulumi.com/ai/answers/c9F7weofui2LaFB1if821v/orchestrating-aws-ec2-instances-with-sfn

Choose your favorite language at bottom of article.

Didier

How to run EC2 instance with Step Function

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