When using lambda to generate elbv2 attributes (name specifically), receiving error from Lambda that name is longer than 32 characters - amazon-web-services

Question

I am building a CloudFormation template that uses a Lambda function to generate the name of the load balancer built by the template.
When the function runs, it fails with the following error:
Failed to validate attributes of ELB arn:aws-us-gov:elasticloadbalancing:us-gov-west-1:273838691273:loadbalancer/app/dev-fu-WALB-18VHO2DJ4MHK/c69c48fd3464de01. An error occurred (ValidationError) when calling the DescribeLoadBalancers operation: The load balancer name 'arn:aws-us-gov:elasticloadbalancing:us-gov-west-1:273838691273:loadbalancer/app/dev-fu-WALB-18VHO2DJ4MHK/c69c48fd3464de01' cannot be longer than '32' characters.
It is obviously pulling the arn rather than the name of the elbv2.
I opened a ticket with AWS to no avail, and also with the company that wrote the script... same results.
I have attached the script and any help is greatly appreciated.
import cfn_resource
import boto3
import boto3.session
import logging
logger = logging.getLogger()
handler = cfn_resource.Resource()
# Retrieves DNSName and source security group name for the specified ELB
#handler.create
def get_elb_attribtes(event, context):
properties = event['ResourceProperties']
elb_name = properties['PORALBName']
elb_template = properties['PORALBTemplate']
elb_subnets = properties['PORALBSubnets']
try:
client = boto3.client('elbv2')
elb = client.describe_load_balancers(
Names=[
elb_name
]
)['LoadBalancers'][0]
for az in elb['AvailabilityZones']:
if not az['SubnetId'] in elb_subnets:
raise Exception("ELB does not include VPC subnet '" + az['SubnetId'] + "'.")
target_groups = client.describe_target_groups(
LoadBalancerArn=elb['LoadBalancerArn']
)['TargetGroups']
target_group_arns = []
for target_group in target_groups:
target_group_arns.append(target_group['TargetGroupArn'])
if elb_template == 'geoevent':
if elb['Type'] != 'network':
raise Exception("GeoEvent Server requires network ElasticLoadBalancer V2.")
response_data = {}
response_data['DNSName'] = elb['DNSName']
response_data['TargetGroupARNs'] = target_group_arns
msg = 'ELB {} found.'.format(elb_name)
logger.info(msg)
return {
'Status': 'SUCCESS',
'Reason': msg,
'PhysicalResourceId': context.log_stream_name,
'StackId': event['StackId'],
'RequestId': event['RequestId'],
'LogicalResourceId': event['LogicalResourceId'],
'Data': response_data
}
except Exception, e:
error_msg = 'Failed to validate attributes of ELB {}. {}'.format(elb_name, e)
logger.error(error_msg)
return {
'Status': 'FAILED',
'Reason': error_msg,
'PhysicalResourceId': context.log_stream_name,
'StackId': event['StackId'],
'RequestId': event['RequestId'],
'LogicalResourceId': event['LogicalResourceId']
}

Answer 1

The error says:
An error occurred (ValidationError) when calling the DescribeLoadBalancers operation
So, looking at where it calls DescribeLoadBalancers:
elb = client.describe_load_balancers(
Names=[
elb_name
]
)['LoadBalancers'][0]
The error also said:
The load balancer name ... cannot be longer than '32' characters.
The name comes from:
properties = event['ResourceProperties']
elb_name = properties['PORALBName']
So, the information is being passed into the Lambda function via event. This is coming from whatever is triggering the Lambda function. So, you'll need to find out what is triggering the function and discover what information it actually sending. Your problem is outside of the code listed.
Other options
In your code, you can send event to the debug logs (eg print (event)) and see whether they are passing the ELB name in a different field.
Alternatively, you could call describe_load_balancers without a Name filter to retrieve a list of all load balancers, then use the ARN (that you have) to find the load balancer of interest. Simply loop through all the results until you find the one that matches the ARN you have. Then, continue as normal.