How to start and stop EC2 instance using Lambda

Question

I am trying to start and stop an EC2 windows instance using lambda, i am using Node.js 8.10 to write the start and stop script.When i am testing the script the script is executed successfully but the EC2 instance is not effected.I am giving the instance details and script below

const AWS = require('aws-sdk');

exports.handler = async (event) => {

const ec2 = new AWS.EC2({ region: event.instanceRegion });
 ec2.stopInstances({ InstanceIds: [event.instanceId] }).promise()
    .then(() => callback(null, `Successfully stopped ${event.instanceId}`))
    .catch(err => callback(err));
};

The script executed successfully

Below is the instance details

This is stop script but this is not able to stop the instance , please help me i am new to aws . Thanks in advance

Answer 1

When using Lambda, your handler function receives three parameters: event, context and callback. You make use of callback when using synchronous functions. When using async you should return a promise.

const AWS = require('aws-sdk');

exports.handler = async (event, context, callback) => {

const ec2 = new AWS.EC2({ region: event.instanceRegion });
 return ec2.stopInstances({ InstanceIds: [event.instanceId] }).promise()
    .then(() => `Successfully stopped ${event.instanceId}`)
    .catch(err => console.log(err));
};

In fact, when you use async keyword you are actually returning a promise, but by returning nothing, you are resolving it with null as response, so your code will just terminate and your stopInstances will not finish their work.