AWS Cloudformation Random Build Fail - amazon-web-services

Question

I'm using Cloudformation to automate instance creation. I'm using an auto scaling group to build a variable number dependent on what i need. However there is a reoccurring issue where at least 1 instance fails to run when i build 2+ instances from this script.
For Example: I state 7 instances for cloudformation to build, 6 will work perfectly but there is always 1 that will not work. There is no error, it just seems to ignore commands. In the userdata section of this script i launch dockers to run in the instance.
I get this error: rpc error code = 13 desc = transport is closing
Can someone take a look to see if doing something wrong or I'm missing a step?
{
"AWSTemplateFormatVersion": "2010-09-09",
"Description": "Test",
"Parameters": {
"InstanceType": {
"Type": "String",
"Default": "t2.large"
},
"NoOfInstances": {
"Type": "String",
"ConstraintDescription": ""
},
"RoleName": {
"Type": "String",
"Default": "**",
"ConstraintDescription": ""
},
"VPCParameter": {
"Type": "AWS::EC2::VPC::Id",
"Default": "**"
},
"SubnetsParameter": {
"Type": "List<AWS::EC2::Subnet::Id>",
"Default": "**"
},
"KeyName": {
"Type": "AWS::EC2::KeyPair::KeyName",
"Default": "**",
"ConstraintDescription": ""
}
},
"Mappings": {
"AWSInstanceType2Arch": {
"t2.large": {
"Arch": "HVM64"
}
},
"AWSRegionArch2AMI": {
"**": {
"HVM64": "**"
}
}
},
"Resources": {
"LaunchConfig": {
"Type": "AWS::AutoScaling::LaunchConfiguration",
"Properties": {
"KeyName": {
"Ref": "KeyName"
},
"IamInstanceProfile": {
"Ref": "RoleName"
},
"SecurityGroups": [{
"Ref": "WebServerSecurityGroup"
}],
"ImageId": {
"Fn::FindInMap": ["AWSRegionArch2AMI",
{
"Ref": "AWS::Region"
}, {
"Fn::FindInMap": ["AWSInstanceType2Arch", {
"Ref": "InstanceType"
}, "Arch"]
}
]
},
"InstanceType": {
"Ref": "InstanceType"
},
"UserData": {
"Fn::Base64": {
"Fn::Join": ["", [ ** ]]
}
}
}
},
"AutoScalingServerGroup": {
"Type": "AWS::AutoScaling::AutoScalingGroup",
"Properties": {
"LaunchConfigurationName": {
"Ref": "LaunchConfig"
},
"MinSize": "1",
"MaxSize": "30",
"Cooldown": "300",
"VPCZoneIdentifier": {
"Ref": "SubnetsParameter"
},
"DesiredCapacity": {
"Ref": "NoOfInstances"
},
"Tags": [ ** ]
}
},
"WebServerSecurityGroup": {
"Type": "AWS::EC2::SecurityGroup",
"Properties": {
"GroupDescription": "**",
"VpcId": {
"Ref": "VPCParameter"
},
"SecurityGroupIngress": [{
"IpProtocol": "tcp",
"CidrIp": "**",
"FromPort": "**",
"ToPort": "**"
}, ]
}
},
"WebServerScaleUpPolicy": {
"Type": "AWS::AutoScaling::ScalingPolicy",
"Properties": {
"AdjustmentType": "ChangeInCapacity",
"AutoScalingGroupName": {
"Ref": "AutoScalingServerGroup"
},
"Cooldown": "60",
"ScalingAdjustment": "1"
}
},
"WebServerScaleDownPolicy": {
"Type": "AWS::AutoScaling::ScalingPolicy",
"Properties": {
"AdjustmentType": "ChangeInCapacity",
"AutoScalingGroupName": {
"Ref": "AutoScalingServerGroup"
},
"Cooldown": "60",
"ScalingAdjustment": "-1"
}
}
}
}

Answer 1

You could be hitting EC2 instance limits - https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-resource-limits.html
You could also look at the Activity History tab for the Auto Scaling Group. See if it has any useful information.