Scheduling EC2 Start and Stop using EventBridge Scheduler

Takahiro Iwasa

Jun 15, 2024

3 min read

EventBridge Scheduler

Many AWS users should use EC2 instances in their daily work. Once the EC2 instances have been started, you will incur costs until stopping them.

Using EventBridge Scheduler, you can automate the starting and stopping process with no application code.

docs.aws.amazon.com

What is Amazon EventBridge Scheduler? - EventBridge Scheduler

Describes key concepts of Amazon EventBridge Scheduler and provides an overview of the topics covered in the EventBridge Scheduler User Guide.

In addition, you can use EventBridge Scheduler with no additional costs up to 14,000,000 invocations per month.

aws.amazon.com

Amazon EventBridge Pricing | Event Bus | Amazon Web Services

With Amazon EventBridge you only pay for events published to your event bus and events ingested for Schema Discovery - no minimum feeds or upfront commitments.

This post describes how to use it with an example.

Replace <SECURITY_GROUP_IDS> and <SUBNET_ID> with the actual value and start an EC2 instance for testing with the following command.

aws ec2 run-instances \
--image-id ami-0f9fe1d9214628296 \
--count 1 \
--instance-type t2.micro \
--security-group-ids <SECURITY_GROUP_IDS> \
--subnet-id <SUBNET_ID>

Create a CloudFormation template with the following content.

AWSTemplateFormatVersion: '2010-09-09'
Description: EC2 scheduler

Parameters:
  Prefix:
    Type: String
    Default: ec2-scheduler
  InstanceIds:
    Type: String
    Description: '"i-1234567890abcdefg", "..."'
  ScheduleStartExpression:
    Type: String
    Default: 'cron(0 7 * * ? *)'
  ScheduleStopExpression:
    Type: String
    Default: 'cron(0 22 * * ? *)'
  ScheduleTimezone:
    Type: String
    Description: IANA timezone identifier. For the full list, refer to https://en.wikipedia.org/wiki/List_of_tz_database_time_zones
    Default: UTC
    AllowedValues:
      - UTC
      - Japan

Resources:
  ScheduleStart:
    Type: AWS::Scheduler::Schedule
    Properties:
      Name: !Sub ${Prefix}-schedule-start
      ScheduleExpression: !Ref ScheduleStartExpression
      ScheduleExpressionTimezone: !Ref ScheduleTimezone
      FlexibleTimeWindow:
        Mode: 'OFF'
      State: ENABLED
      Target:
        Arn: arn:aws:scheduler:::aws-sdk:ec2:startInstances
        Input: !Sub |-
          {
            "InstanceIds": [${InstanceIds}]
          }
        RoleArn: !GetAtt Role.Arn

  ScheduleStop:
    Type: AWS::Scheduler::Schedule
    Properties:
      Name: !Sub ${Prefix}-schedule-stop
      ScheduleExpression: !Ref ScheduleStopExpression
      ScheduleExpressionTimezone: !Ref ScheduleTimezone
      FlexibleTimeWindow:
        Mode: 'OFF'
      State: ENABLED
      Target:
        Arn: arn:aws:scheduler:::aws-sdk:ec2:stopInstances
        Input: !Sub |-
          {
            "InstanceIds": [${InstanceIds}]
          }
        RoleArn: !GetAtt Role.Arn

  Role:
    Type: AWS::IAM::Role
    Properties:
      RoleName: !Sub ${Prefix}-role
      AssumeRolePolicyDocument:
        Version: 2012-10-17
        Statement:
          - Effect: Allow
            Principal:
              Service:
                - scheduler.amazonaws.com
            Action:
              - sts:AssumeRole
      Policies:
        - PolicyName: ec2
          PolicyDocument:
            Version: 2012-10-17
            Statement:
              - Effect: Allow
                Action:
                  - ec2:StartInstances
                  - ec2:StopInstances
                Resource: !Sub arn:aws:ec2:${AWS::Region}:${AWS::AccountId}:instance/i-*

Replace <INSTANCE_ID> with the actual value and deploy the CloudFormation stack with the following command.

aws cloudformation deploy \
--template-file ./template.yaml \
--stack-name ec2-scheduler \
--parameter-overrides InstanceIds='"<INSTANCE_ID1>", "<INSTANCE_ID2>"' \
--capabilities CAPABILITY_NAMED_IAM

The provisioned EventBridge scheduler will start the EC2 instances at 7 a.m. and stop at 10 p.m. If you want to change the scheduling time, specify ScheduleStartExpression and ScheduleStopExpression at the CloudFormation stack deployment.

Please confirm the EC2 instances are started and stopped as expected.

Clean up the provisioned AWS resources with the following command.

aws ec2 terminate-instances --instance-ids <INSTANCE_IDS>
aws cloudformation delete-stack --stack-name ec2-scheduler

If you are using EC2 instances for development purposes, EventBridge Scheduler offers a cost-saving solution.

Since EventBridge Scheduler can run actions of other services than EC2, you can utilize it to automate scheduled maintenance.

I hope you will find this post useful.