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Federico Navarrete
Federico Navarrete

Posted on • Updated on • Originally published at supernovaic.blogspot.com

How to schedule EC2 instances easily (start/stop)

Everyone would like to schedule EC2 instances and save a couple of bucks. Today, I'm bringing you a small Python that can help you. The steps are the following ones:

Step 1. Create a lambda function called: ec2_scheduler

Step 2. Copy and paste the following code:

import boto3
import os
import json

region = os.environ['REGION']
ec2 = boto3.client('ec2', region_name=region)

instances = []

def lambda_handler(event, context):
    action = event['Action']
    response = ec2.describe_instances(Filters=[{'Name' : 'instance-state-name','Values' : [action]}, {'Name': 'tag-key', 'Values': ['auto-scheduled']}])
    reservations = response['Reservations']
    for reservation in reservations:
        for instance in reservation['Instances']:
            instanceId = instance['InstanceId']
            for tag in instance['Tags']:
                if tag['Key'] == 'auto-scheduled' and tag['Value'] == 'true':
                    instances.append(instanceId)

    if (action == 'stopped'):
        if (len(instances) > 0):
            ec2.start_instances(InstanceIds=instances)
    else
        if (len(instances) > 0):
            ec2.stop_instances(InstanceIds=instances)
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Step 3. Set a tag to your EC2 instance called: auto-scheduled that has a value assigned as true.

Step 4. Add a new Policy in the configuration and permission section of your Lambda that contains:

{
    "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*",
                "ec2:Describe*"
            ],
            "Resource": "*"
        }
    ]
}
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Step 5. Schedule your Lambda as triggers with cron expressions like these ones:

  • For starting: cron(0 6 ? * MON-FRI *)
  • For stopping: cron(0 16 ? * MON-FRI *)

Step 6. Set a JSON that contains the following expression to know if it's starting or stopping:

  • For starting:
{
    "Action": "stopped"
}
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  • For stopping:
{
    "Action": "running"
}
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And that's all!

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Banner credits:

https://tridentsys.net/howto-schedule-ec2/

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