Problem Statement:- As soon as a row gets added to the Dynamodb
Table, launch an EC2 machine and use the Key column value of the table as the
tag name for the instance.
Solution:-
Things we will
need to do:-
1. Create the Dynamodb Table.
2. Create a role (EC2 access and dynamodb access)
for the lambda function that you will be creating.
3. Create lambda function with Dynamodb Trigger.
4. Test.
Before we start,
just some names that you should know that I have used in the example -
Lambda Function
Name: Dynamo_Trigger_Ec2_Function_v2
Dynamodb Table
Name: Dynamo_Trigger
Dynamodb Table
Attributes:
Key - Item_Id
Step 1:-
Before we dive
into how to use lambda functions and it’s details, we need to have a Dynamodb
Table in place for the current problem statement.
Creating a table
is pretty straight forward. You can refer the links below :-
Dynamodb :-
Step 2:-
Before you start
creating a lambda function, you need to assign it an Execution Role so that
lambda has the permission to access Dynamodb and EC2.
We will be giving
EC2 Access and Dynamodb Access.
We are also going
to give it some policies to be able to write logs in CloudWatch.
The policy is -
{
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Step 3:-
Select DynamoDB
from the drop-down list.
Make sure you
select the right table for the trigger.
You can enable the trigger from now itself or you
can enable it later too after creating the function.
Below the code
entry type - you will have to insert your code.
'use strict';
console.log('Loading function');
exports.handler = (event, context, callback)
=> {
//console.log('Received event:', JSON.stringify(event, null, 2));
//var
docClient = new AWS.DynamoDB.DocumentClient();
var
tag_name;
var
event_name;
var
AWS = require('aws-sdk');
AWS.config.region = 'us-east-1';
var
ec2 = new AWS.EC2();
var
params = {
ImageId: 'ami-a4827dc9', /* Use this AMI ID for now */
MaxCount: 1,
MinCount: 1,
DryRun: false,
EbsOptimized: false,
InstanceType: 't2.micro',
KeyName: 'US-EAST-CLOUDAPI-LB-key',
Monitoring: {
Enabled: false
},
Placement: {
Tenancy: 'default'
},
SecurityGroupIds: [
'sg-436abe3b',
],
SubnetId: 'subnet-5877fa2e',
};
event.Records.forEach((record) => {
console.log(record.eventID);
event_name = record.eventName;
switch(event_name){
case "INSERT":
console.log('DynamoDB Record: %j', record.dynamodb);
tag_name = record.dynamodb.Keys.Item_Id.S; // adding instance tag as
the same key column value from the db.
console.log(tag_name);
// Create the instance
ec2.runInstances(params, function(err, data) {
if (err) {
console.log("Could not create instance", err); return; }
var instanceId =
data.Instances[0].InstanceId;
console.log("Created
instance", instanceId);
// Add tags to the
instance
params = {Resources:
[instanceId], Tags: [
{Key: 'Name', Value:
tag_name}
]};
ec2.createTags(params,
function(err) {
console.log("Tagging instance", err ? "failure" :
"success");
});
});
break;
case "REMOVE":
console.log('DynamoDB Record:
%j', record.dynamodb);
//console.log('key value: %j', record.dynamodb.Keys.Item_Id.S);
console.log("Since it's a REMOVE so not doing anything.");
}
});
callback(null, `Successfully processed ${event.Records.length}
records.`);
};
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After the code,
AWS will pre-populate the Handler field for you. It is the
filename.handler-function.
Step 4:-
You should see an EC2 machine getting launched
with the tag same as the Key Column value in your database.
Like in the example here, I added Item_Id =
dummy, so in my EC2 console I can see an instance getting launched with the tag
“dummy”.
Also go to your CloudWatch Logs - you should see
a new Log Group created with the same name as your Lambda Function. Inside the
group you can see all your logs getting accumulated.
Good explanation,thanks for writing,it is useful for so many developers
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Thank you!
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