Optimize EC2 cost with Lambda > Create Lambda Function > Function start instance

Function start instance

Create Lambda Function to start instances

In the Lambda Function interface

Select Create function

Lambda Function start instance

In the Create function interface

Select Author from scratch
Function name, enter dc-common-lambda-auto-start
Runtime, select Python 3.14
Select x86_64

Lambda Function start instance

In the Create function interface

Select Change default execution role
Select Use an existing role
Select dc-common-lambda-role
Select Create function

Lambda Function start instance

Before importing the code, create the following Environment variables:

Select Configuration
Select Environment variables
Select Edit

Lambda Function start instance

In the Edit environment variables interface

Key, enter environment_auto
Value, enter true
Select Save

Lambda Function start instance

After creating the environment

Select Code
Import source code: You need to change the webhook_url to receive notifications to Slack.

import boto3
import os
import json
import logging
import urllib3

logger = logging.getLogger()
logger.setLevel(logging.INFO)

ec2_resource = boto3.resource('ec2')
http = urllib3.PoolManager()
webhook_url = "https://hooks.slack.com/services/XXXXX/XXXXX/XXXXX"  # Replace with your Webhook URL

def lambda_handler(event, context):
    environment_auto = os.environ.get('environment_auto')
    if not environment_auto:
        logger.info('Target is empty')
        return {
            "statusCode": 400,
            "body": "Environment variable 'environment_auto' is not set"
        }

    instances = ec2_resource.instances.filter(
        Filters=[{'Name': 'tag:environment_auto', 'Values': [environment_auto]}]
    )

    instance_list = list(instances)
    if not instance_list:
        return {
            "statusCode": 500,
            "body": "Target Instance is None"
        }

    action_start = instances.start()
    send_slack(action_start)
    return {
        "statusCode": 200,
        "body": "EC2 Starting"
    }


def send_slack(action_start):
    list_instance_id = []
    if (
        len(action_start) > 0
        and "StartingInstances" in action_start[0]
        and len(action_start[0]["StartingInstances"]) > 0
    ):
        for instance in action_start[0]["StartingInstances"]:
            list_instance_id.append(instance["InstanceId"])

        msg = f"Starting Instances ID:\n {list_instance_id}"
        data = {"text": msg}
        http.request(
            "POST",
            webhook_url,
            body=json.dumps(data).encode("utf-8"),
            headers={"Content-Type": "application/json"}
        )
    else:
        logger.info('Not found Instances Start')

Save and select Deploy

Lambda Function start instance

Next, create a schedule on EventBridge Scheduler

Access Amazon EventBridge
In the left menu, select Schedules (or Scheduler > Schedules)
Select Create schedule

In Step 1: Specify schedule detail

Schedule name: enter dc-common-lambda-auto-start
Description: enter dc-common-lambda-auto-start
In the Schedule pattern section:
- Select Recurring schedule
- Schedule type: select Rate-based schedule
- Rate expression: enter 8 and select hours for the unit
- For Flexible time window: select Off
Select Next

Lambda Function start instance

In Step 2: Select target

From the list of targets, select AWS Lambda (or search for Lambda Invoke)
Lambda function: select the dc-common-lambda-auto-start function
Select Next

In Step 3: Settings

Keep the default settings (Execution role, Retry policy…)
Select Next

Lambda Function start instance

In Step 4: Review and create schedule

Review all information
Select Create schedule to complete scheduling the Lambda Function to start EC2 instances automatically.