[AWS] Lab: Lambda

Solution Outline

To run our function we use a service called CloudWatch, which periodically generates events. Those events are sent to the Lambda function, and on each event, the Lambda function gets a list of instances from the environment and will randomly terminate one of them. (see below the summary diagram)

You can find the code for this demo in the course repo: https://github.com/udacity/cloud-developer/tree/master/course-04/exercises/c4-demos-master/04-chaos-monkey

In the 04-chaos-monkey directory install the dependencies:

npm install

and then zip the folder so that it can be uploaded.

zip -r chaos-monkey.zip .

Create a Lambda function

1. Create a empty Node.js v10.x lambda function

2. Upload  

chaos-monkey.zip

Get some running EC2 instances

Following the post: Host a Static Webpage, running two EC2 instance with public HTTP access.

Create a CloudWatch Event

So every 1 min, it will trigger Lambda `chaos-monkey` function.

After 1 min, we can see that Function has been triggered but with error result:

We can fix this by add EC2's List and TerminateInstance policy to the Role.

Fix IAM policy

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": "logs:CreateLogGroup",
            "Resource": "arn:aws:logs:us-east-1:645307551852:*"
        },
        {
            "Effect": "Allow",
            "Action": [
                "ec2:TerminateInstances",
                "ec2:DescribeInstances"
            ],
            "Resource": "*"
        }
    ]
}

After that, it should work as expected. Every 1 min, cloudwatch will trigger a lambda function to turn off EC2 instances that are running.  You can configure EC2 that it will automatcilly bring up again.