Schedule to start an EC2 instance and run a python script within it

For future developers, who come to this question, a newer approach to this is:

1. Create your EC2 with a role containing AmazonEC2RoleforSSM policy
2. Create a lambda to do the wake-up, run command, shutdown
3. Use a Cloudwatch Event to trigger the lambda

So:

1. Follow the steps here: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-roles-for-amazon-ec2.html

2. Use the following lambda skeleton:

import time
import boto3

REGION_NAME = 'us-east-1'

WORKING_DIRECTORY = '<YOUR WORKING DIRECTORY, IF ANY>'

COMMAND = """
    echo "Hello, world!"
    """

INSTANCE_ID = '<YOUR INSTANCE ID>'


def start_ec2():
    ec2 = boto3.client('ec2', region_name=REGION_NAME)
    ec2.start_instances(InstanceIds=[INSTANCE_ID])

    while True:
        response = ec2.describe_instance_status(InstanceIds=[INSTANCE_ID], IncludeAllInstances=True)
        state = response['InstanceStatuses'][0]['InstanceState']

        print(f"Status: {state['Code']} - {state['Name']}")

        # If status is 16 ('running'), then proceed, else, wait 5 seconds and try again
        if state['Code'] == 16:
            break
        else:
            time.sleep(5)

    print('EC2 started')


def stop_ec2():
    ec2 = boto3.client('ec2', region_name=REGION_NAME)
    ec2.stop_instances(InstanceIds=[INSTANCE_ID])

    while True:
        response = ec2.describe_instance_status(InstanceIds=[INSTANCE_ID], IncludeAllInstances=True)
        state = response['InstanceStatuses'][0]['InstanceState']

        print(f"Status: {state['Code']} - {state['Name']}")

        # If status is 80 ('stopped'), then proceed, else wait 5 seconds and try again
        if state['Code'] == 80:
            break
        else:
            time.sleep(5)

    print('Instance stopped')


def run_command():
    client = boto3.client('ssm', region_name=REGION_NAME)

    time.sleep(10)  # I had to wait 10 seconds to "send_command" find my instance 

    cmd_response = client.send_command(
        InstanceIds=[INSTANCE_ID],
        DocumentName='AWS-RunShellScript',
        DocumentVersion="1",
        TimeoutSeconds=300,
        MaxConcurrency="1",
        CloudWatchOutputConfig={'CloudWatchOutputEnabled': True},
        Parameters={
            'commands': [COMMAND],
            'executionTimeout': ["300"],
            'workingDirectory': [WORKING_DIRECTORY],
        },
    )

    command_id = cmd_response['Command']['CommandId']
    time.sleep(1)  # Again, I had to wait 1s to get_command_invocation recognises my command_id

    retcode = -1
    while True:
        output = client.get_command_invocation(
            CommandId=command_id,
            InstanceId=INSTANCE_ID,
        )

        # If the ResponseCode is -1, the command is still running, so wait 5 seconds and try again
        retcode = output['ResponseCode']
        if retcode != -1:
            print('Status: ', output['Status'])
            print('StdOut: ', output['StandardOutputContent'])
            print('StdErr: ', output['StandardErrorContent'])
            break

        print('Status: ', retcode)
        time.sleep(5)

    print('Command finished successfully') # Actually, 0 means success, anything else means a fail, but it didn't matter to me
    return retcode


def lambda_handler(event, context):
    retcode = -1
    try:
        start_ec2()
        retcode = run_command()
    finally:  # Independently of what happens, try to shutdown the EC2
        stop_ec2()

    return retcode

3. Follow the steps here: https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/RunLambdaSchedule.html

I was having problems starting and stopping the instance using the solutions in this post. Then I followed the instructions on https://aws.amazon.com/premiumsupport/knowledge-center/start-stop-lambda-cloudwatch/ and it was really easy. Basically:

1. Go to https://console.aws.amazon.com/iam/home#/home and on the left side, click Policies and click Create Policy. Then click on the JSON tab. Then copy paste this to create a new policy:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "logs:CreateLogGroup",
        "logs:CreateLogStream",
        "logs:PutLogEvents"
      ],
      "Resource": "arn:aws:logs:*:*:*"
    },
    {
      "Effect": "Allow",
      "Action": [
        "ec2:Start*",
        "ec2:Stop*"
      ],
      "Resource": "*"
    }
  ]
}

2. Go to https://console.aws.amazon.com/iam/home#/home and on the left choose Roles. Make sure you choose Lambda as your AWS Service, and attach the policy you created in Step 1.

3. Then go to the Lambda console, click Create Function. Choose Python 3.7 and then click the dropdown next to Permissions and Use An Existing Role and attach the IAM role you created in Step 2.

4. Use this as your code:

import boto3
region = 'us-west-1' # Dont use the specific, like instead of us-east-1d just write us-east-1
instances = ['i-xxxxxxxxxxxx']
ec2 = boto3.client('ec2', region_name=region)

def lambda_handler(event, context):
    ec2.start_instances(InstanceIds=instances)
    print('started your instances: ' + str(instances))

5. Start your EC2 instance, and type which python to find your path to python and write this down. Then, type in crontab -e to edit your CRON jobs. Don't use sudo...because sometimes sudo messes things up when you haven't been using it to run the Python files. In my instance, I had a pgpass file storing my password that sudo couldn't see , but removing sudo worked!
6. Within the crontab editor after the commented lines, type in @reboot /path/to/python /path/to/file.py For example, for me this was @reboot /home/init/python /home/init/Notebooks/mypredictor.py
7. At the end of your Python file, you need to stop your instance. You can do it like this:

import boto3
region = 'us-west-1' # Dont use the specific, like instead of us-east-1d just write us-east-1
instances = ['i-xxxxxxxxxxxx']
ec2 = boto3.client('ec2', region_name=region)

ec2.stop_instances(InstanceIds=instances)