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September 5, 2022 11:12
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Fetch IPv6 address of EC2 instance for creating AAAA DNS record
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# large parts taken from https://aws.amazon.com/blogs/mt/four-ways-to-retrieve-any-aws-service-property-using-aws-cloudformation-part-1/ | |
AWSTemplateFormatVersion: '2010-09-09' | |
Parameters: | |
ExampleServiceInstanceName: | |
Default: Example | |
Description: Instance and Host Name | |
Type: String | |
Resources: | |
ExampleService: | |
Properties: | |
ImageId: ami-09e0d6fdf60750e33 # Ubuntu Server 20.04 LTS (HVM), SSD Volume Type, (64-bit Arm) | |
InstanceType: t4g.small | |
KeyName: example.key | |
SubnetId: subnet-123456789 # <- insert your subnet here | |
Type: AWS::EC2::Instance | |
ExampleDnsRecordAAAA: | |
Properties: | |
Comment: A record for the Example server. | |
HostedZoneId: Z1234567890 # <- insert your hosted zone id here | |
Name: | |
Fn::Join: | |
- . | |
- - !Ref ExampleServiceInstanceName | |
- Z1234567890 # <- insert your hosted zone id here | |
ResourceRecords: | |
- Fn::GetAtt: CustomIpv6Resource.Ipv6Address | |
TTL: 900 | |
Type: AAAA | |
Type: AWS::Route53::RecordSet | |
# | |
# CustomResource for fetching IPv6 address | |
# | |
LambdaBasicExecutionRole: | |
Type: AWS::IAM::Role | |
Properties: | |
AssumeRolePolicyDocument: | |
Statement: | |
- Effect: Allow | |
Principal: | |
Service: lambda.amazonaws.com | |
Action: sts:AssumeRole | |
Path: / | |
Policies: | |
- PolicyName: CustomLambdaEC2DescribePolicy | |
PolicyDocument: | |
Version: '2012-10-17' | |
Statement: | |
- Effect: Allow | |
Action: | |
- logs:CreateLogGroup | |
- logs:CreateLogStream | |
- logs:PutLogEvents | |
Resource: arn:aws:logs:*:*:* | |
- Effect: Allow | |
Action: | |
- ec2:DescribeNetworkInterfaces | |
Resource: '*' | |
CustomIpv6Resource: | |
Type: AWS::CloudFormation::CustomResource | |
Properties: | |
ServiceToken: !GetAtt 'CustomFunction.Arn' | |
ResourceRef: !Ref ExampleService | |
CustomFunction: | |
Type: AWS::Lambda::Function | |
Properties: | |
Handler: index.lambda_handler | |
Description: "Retrieves IPv6 address of EC2 instance" | |
Timeout: 30 | |
Role: !GetAtt 'LambdaBasicExecutionRole.Arn' | |
Runtime: python3.7 | |
Code: | |
ZipFile: | | |
import json | |
import logging | |
import cfnresponse | |
import boto3 | |
logger = logging.getLogger() | |
logger.setLevel(logging.INFO) | |
def lambda_handler(event, context): | |
logger.info('got event {}'.format(event)) | |
try: | |
responseData = {} | |
if event['RequestType'] == 'Delete': | |
logger.info('Incoming RequestType: Delete operation') | |
cfnresponse.send(event, context, cfnresponse.SUCCESS, {}) | |
if event['RequestType'] in ["Create", "Update"]: | |
# 1. retrieve resource reference ID or Name | |
ResourceRef=event['ResourceProperties']['ResourceRef'] | |
# 2. retrieve boto3 client | |
client = boto3.client('ec2') | |
# 3. Invoke describe/retrieve function using ResourceRef | |
response = response=client.describe_network_interfaces(Filters=[{'Name':'attachment.instance-id', 'Values':[ResourceRef] }]) | |
# 4. Parse and return required attributes | |
responseData = {} | |
responseData['Ipv6Address'] = response.get('NetworkInterfaces')[0]['Ipv6Addresses'][0]['Ipv6Address'] | |
logger.info('Retrieved IPv6 address!') | |
cfnresponse.send(event, context, cfnresponse.SUCCESS, responseData) | |
else: | |
logger.info('Unexpected RequestType!') | |
cfnresponse.send(event, context, cfnresponse.SUCCESS, responseData) | |
except Exception as err: | |
logger.error(err) | |
responseData = {"Data": str(err)} | |
cfnresponse.send(event,context,cfnresponse.FAILED,responseData) |
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