ecs-scheduled-lambda.md

Cost-Efficient ECS services with Scheduled Lambda

Background

Get ECS scheduled task running or starting can easily be enabled from ECS Task Scheduler or CloudWatch Events. Learn more.

But for STOPPING Tasks, I cannot find any. However, I can manually set DesiredCount in ECS service to 0. Learn more.

The goal is to schedule ECS Container service to run on 9am - 6pm only, thus, cost-efficient for development environment.

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Solution

This solution will create the following resources:

• A lambda function, to start or stop by update the ECS service DesiredCount.
• A scheduled CloudWatch Events, to start the ECS tasks.
• A scheduled CloudWatch Events, to stop the ECS tasks.

Lambda Function that will start or stop the ECS service based on the input from CloudWatch Events:

    if(event.status == 'stop'){
        var params = {
            cluster: process.env.ECS_CLUSTER,
            service: process.env.ECS_SERVICE_NAME,
            desiredCount: 0
        };
    }
    else{
        var params = {
            cluster: process.env.ECS_CLUSTER,
            service: process.env.ECS_SERVICE_NAME,
            desiredCount: 1
        };
    }
    
    var ecs = new AWS.ECS();
    ecs.updateService(params, function (err, data) {
        if (err) console.log(err, err.stack); // an error occurred
        else console.log(data);           // successful response
    });

In Cloudformation template, create resources that will invoke the Lambda Function on a schedule:

  StartEcsLambdaSchedule:
    Type: AWS::Events::Rule
    Properties:
      Description: >
        A schedule for the Lambda function to start ECS service during office hours.
      ScheduleExpression: !Ref StartEcsLambdaScheduleExpression
      State: ENABLED
      Targets:
        - Arn: !Sub ${EcsTaskScheduleLambdaFunction.Arn}
          Id: StartEcsLambdaScheduleV1
          Input: '{"status": "start"}'
  
  StopEcsLambdaSchedule:
    Type: AWS::Events::Rule
    Properties:
      Description: >
        A schedule for the Lambda function to stop ECS service after office hours.
      ScheduleExpression: !Ref StopEcsLambdaScheduleExpression
      State: ENABLED
      Targets:
        - Arn: !Sub ${EcsTaskScheduleLambdaFunction.Arn}
          Id: StopEcsLambdaScheduleV1
          Input: '{"status": "stop"}'