AWS Lambda function to set an Auto Scaling instance to be Unhealthy in response to a SNS message

myFunction.js

console.log('Loading event');
var aws = require('aws-sdk');
var s3 = new aws.S3({apiVersion: '2006-03-01'});
var autoscaling = new aws.AutoScaling({apiVersion: '2011-01-01'});

exports.handler = function(event, context) {
   console.log('Received event:');
   console.log(event);
   //console.log(typeof event.Subject);
   if (event.hasOwnProperty('Message')) {
       var msg = event.Message.replace(/!!/g,'"');
       var instance_id = JSON.parse(msg).Trigger.Dimensions[0].value;
       console.log('Changing instance health for: ' + instance_id);
       var params = {
           HealthStatus: 'Unhealthy', /* required */
           InstanceId: instance_id, /* required */
           ShouldRespectGracePeriod: false
       };
    
        autoscaling.setInstanceHealth(params, function(err, data) {
            if (err) {
                console.log(err, err.stack); // an error occurred
                context.done('error','error: '+err);
            }
            else {
                console.log(data);           // successful response
                context.done(null,'');
            }
        });
   }
   else {
       console.log('No message');
       context.done(null,'');
   }
};