AWS Cloudformation failing to acknowledge AutoScalingGroup - amazon-web-services

Question

While using CloudFormation to create EC2 instance along with an autoscaling group, I face the error:
The following resource(s) failed to create: [WebsInstanceServerGroup].
image of CloudFormation Group output
The failure is seen while creating auto scaling group, but when I check the auto scaling group console, it says that the creation was 'successful.' (The 'in-progress' deletion happens after a 15 minute time out value from CloudFormation).
image of AutoScaling output
What could be the reason CloudFormation is not acknowledging that the AutoScale group is created successfully?
The error also says something about WebInstanceServerGroup, so I checked my template for that, but saw nothing suspicious.
"WebsInstanceServerGroup": {
"Type": "AWS::AutoScaling::AutoScalingGroup",
"Properties": {
"AvailabilityZones": {
"Fn::GetAZs": "AWS::Region"
},
"VPCZoneIdentifier": {
"Ref": "WebsELBSubnetId"
},
"LoadBalancerNames": [
{
"Ref": "WebsELB"
}
],
"LaunchConfigurationName": {
"Ref": "WebsEC2Instance"
},
"Cooldown": 300,
"HealthCheckGracePeriod": 600,
"HealthCheckType": "EC2",
"Tags": [
{
"Key": "Name",
"Value": {
"Ref": "WebsInstanceName"
},
"PropagateAtLaunch": "true"
},
{
"Key": "Service",
"Value": {
"Ref": "ServiceTag"
},
"PropagateAtLaunch": "true"
}
],
"MinSize": {
"Ref": "ASGMin"
},
"DesiredCapacity": {
"Ref": "ASGDesired"
},
"MaxSize": {
"Ref": "ASGMax"
}
},
"CreationPolicy": {
"ResourceSignal": {
"Count": {
"Ref": "ASGMin"
},
"Timeout": "PT15M"
}
}
}
Please let me know if more information is required, thanks in advance.

Answer 1

Looks like your EC2 instances in your autoscaling group are not sending the required success signals.
CloudFormation will wait for you to send ASGMin signals before considering your WebsInstanceServerGroup to be successfully created. So if ASGMin is set to 3, each of your 3 EC2 instances should send a signal.
To send the signal you can either use the cfn-signal helper, or with the AWS CLI:
aws cloudformation signal-resource \
--stack-name {your stack name here} \
--status SUCCESS \
--logical-resource-id WebsInstanceServerGroup \
--unique-id {the instance ID for the EC2 instance that is sending the signal}
Use this command at the end of your User Data script, when you consider your EC2 instance to be fully provisioned and ready to go.