What you're tring to do (schedule Lambda from Lambda) it's not possible with the current AWS services.
So, in order to avoid an always-on ec2 instance, there are other options:
1) Use AWS default or custom metrics. You can use, for example, ApproximateNumberOfMessagesVisible or CPUUtilization (if your app fires a big CPU utilization when process a request). You can also create a custom metric and fire it when your instance is idle (depending on the app that's running in your instance).
The problem with this option is that you'll waste already paid minutes (AWS always charge a full-hour, no matter if you used your instance for 15 minutes).
2) A better option, in my opinion, would be to run a Lambda function once per minute to check if your instances are idle and shut them down only if they are close to the full hour.
import boto3
from datetime import datetime
def lambda_handler(event, context):
print('ManageInstances function executed.')
environments = [['instance-id-1', 'SQS-queue-url-1'], ['instance-id-2', 'SQS-queue-url-2'], ...]
ec2_client = boto3.client('ec2')
for environment in environments:
instance_id = environment[0]
queue_url = environment[1]
print 'Instance:', instance_id
print 'Queue:', queue_url
rsp = ec2_client.describe_instances(InstanceIds=[instance_id])
if rsp:
status = rsp['Reservations'][0]['Instances'][0]
if status['State']['Name'] == 'running':
current_time = datetime.now()
diff = current_time - status['LaunchTime'].replace(tzinfo=None)
total_minutes = divmod(diff.total_seconds(), 60)[0]
minutes_to_complete_hour = 60 - divmod(total_minutes, 60)[1]
print 'Started time:', status['LaunchTime']
print 'Current time:', str(current_time)
print 'Minutes passed:', total_minutes
print 'Minutes to reach a full hour:', minutes_to_complete_hour
if(minutes_to_complete_hour <= 2):
sqs_client = boto3.client('sqs')
response = sqs_client.get_queue_attributes(QueueUrl=queue_url, AttributeNames=['All'])
messages_in_flight = int(response['Attributes']['ApproximateNumberOfMessagesNotVisible'])
messages_available = int(response['Attributes']['ApproximateNumberOfMessages'])
print 'Messages in flight:', messages_in_flight
print 'Messages available:', messages_available
if(messages_in_flight + messages_available == 0):
ec2_resource = boto3.resource('ec2')
instance = ec2_resource.Instance(instance_id)
instance.stop()
print('Stopping instance.')
else:
print('Status was not running. Nothing is done.')
else:
print('Problem while describing instance.')
