lamda-function.md

1. Give permission to user

   1. AWS Managed Policy: AWSLambda_FullAccess
   2. AWS Managed Policy: AmazonEventBridgeFullAccess
   3. AWS Managed Policy: CloudWatchLogsFullAccess
   

2. Create a Lambda Execution Role => Name => lambda-ec2-start-stop-role

   AmazonEC2FullAccess
   AWSLambdaBasicExecutionRole
   and share the Role ARN with me.
   

3. Cron Job Command

   Your Schedule

   Action	Pakistan Time	UTC Time
   Start	8:30 AM Mon-Fri	3:30 AM UTC
   Stop	7:30 PM Mon-Fri	2:30 PM UTC

4. Cron Expressions

   Start Instances — 8:30 AM PKT (Mon-Fri)

   cron(30 3 ? * MON-FRI *)
   

   Stop Instances — 7:30 PM PKT (Mon-Fri)

   cron(30 14 ? * MON-FRI *)
   

   How to Read This Cron

   cron(Minutes  Hours  Day-of-Month  Month  Day-of-Week  Year)
         30       3         ?           *      MON-FRI      *
         
         
   30 → 30 minutes
   3 → 3 AM UTC (= 8:30 AM PKT)
   ? → any day of month (we're using day-of-week instead)
   * → every month
   MON-FRI → Monday to Friday only (Saturday & Sunday automatically skipped)
   * → every year
   

5. Start Code

   import boto3
   from botocore.config import Config
   
   ec2_config = Config(region_name='us-east-1')
   ec2 = boto3.client('ec2', config=ec2_config)
   
   def get_instances():
       return [
           item["Instances"][0]["InstanceId"]
           for item in ec2.describe_instances(
               Filters=[
                   {'Name': 'instance-state-name', 'Values': ['stopped']},
                   {'Name': 'tag:AutoSchedule', 'Values': ['true']} 
               ]
           ).get("Reservations")
       ]
   
   def start_instances(instance_ids):
       ec2.start_instances(InstanceIds=instance_ids)
   
   def lambda_handler(event, context):
       instances = get_instances()
       print(f"Starting the instances {instances}")
       start_instances(instances)
   

6. Stop

   import boto3
   from botocore.config import Config
   
   ec2_config = Config(region_name='us-east-1')
   ec2 = boto3.client('ec2', config=ec2_config)
   
   def get_instances():
       return [
           item["Instances"][0]["InstanceId"]
           for item in ec2.describe_instances(
               Filters=[
                   {'Name': 'instance-state-name', 'Values': ['running']},
                   {'Name': 'tag:AutoSchedule', 'Values': ['true']} 
                   ]
           ).get("Reservations")
       ]
   
   def stop_instances(instance_ids):
       ec2.stop_instances(InstanceIds=instance_ids, Force=True)
   
   def lambda_handler(event, context):
       instances = get_instances()
       print(f"Stopping the instances {instances}")
       stop_instances(instances)
   

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