Hi Folks, I’m writing this post to share – on how we used CloudFormation to manage AWS resources and exploited AWS CloudFormation application bootstrap helper scripts to register EC2 machines with Chef server for automation.
AWS CloudFormation’s templates describe the AWS resources, and any associated dependencies or runtime parameters, required to run your application.
To better use CloudFormation templates – Instead of using single CloudFormation template for whole setup we created different templates for launching different AWS resources and further launched each template in a different CloudFormation stack, for example – a template for launching RDS instances, a template for launching tomcat instances, a template for launching nginx instances.
Please find below the example template we created for launching tomcat instances using AWS Auto Scaling to automatically scale tomcat instances capacity up or down according to conditions defined. We also used AWS CloudFormation application bootstrap helper scripts to register EC2 machines with Chef server for automation as shown below:
{
"AWSTemplateFormatVersion" : "2010-09-09",
"Description" : "AWS CloudFormation Sample Template for launching Tomcat instance(s) in Autoscaling group",
"Parameters" : {
"ChefEnvironment" : {
"Description" : "Name of Chef environment in which you launch this tomcat instance(s)",
"Type" : "String"
},
"KeyName" : {
"Description" : "Name of and existing EC2 KeyPair to enable SSH access to the instance",
"Type" : "String"
},
"TomcatAmi" : {
"Description" : "Name of an existing Tomcat AMI to use",
"Type" : "String"
},
"InstanceType" : {
"Description" : "WebServer EC2 instance type",
"Type" : "String",
"Default" : "m1.small",
"AllowedValues" : [ "t1.micro","m1.small","m1.medium","m1.large","m1.xlarge","m2.xlarge","m2.2xlarge","m2.4xlarge","c1.medium","c1.xlarge","cc1.4xlarge","cc2.8xlarge","cg1.4xlarge"],
"ConstraintDescription" : "must be a valid EC2 instance type."
},
"Subnets" : {
"Type" : "CommaDelimitedList",
"Description" : "The list of SubnetIds in your Virtual Private Cloud (VPC)"
},
"AZs" : {
"Type" : "CommaDelimitedList",
"Description" : "The list of AvailabilityZones for your Virtual Private Cloud (VPC)"
},
"AccessKey" : {
"Description" : "Access Key to use for cloud init",
"Type" : "String",
"NoEcho": "true"
},
"SecretKey" : {
"Description" : "Secret Key",
"Type" : "String",
"NoEcho": "true"
},
"ChefRole" : {
"Description" : "Name of the chef role to add to this tomcat instance(s)",
"Type" : "String"
},
"SecurityGroup" : {
"Type" : "String",
"Description" : "Security Group ID in your VPC in which this particular instance shall launch "
},
"InstanceCount" : {
"Description" : "Number of EC2 instances to launch",
"Type" : "Number",
"Default" : "3"
}
},
"Resources" : {
"WebServerGroup" : {
"Type" : "AWS::AutoScaling::AutoScalingGroup",
"Properties" : {
"AvailabilityZones" : { "Ref" : "AZs" },
"VPCZoneIdentifier" : { "Ref" : "Subnets" },
"LaunchConfigurationName" : { "Ref" : "LaunchConfig" },
"MinSize" : "2",
"MaxSize" : "10",
"DesiredCapacity" : { "Ref" : "InstanceCount" }
}
},
"LaunchConfig" : {
"Type" : "AWS::AutoScaling::LaunchConfiguration",
"Metadata" : {
"AWS::CloudFormation::Init" : {
"config" : {
"packages" : {
},
"sources" : {
},
"commands" : {
},
"files" : {
"/etc/chef/validation.pem" : {
"source" : "https://s3-us-west-2.amazonaws.com/nclouds/chef/validation.pem",
"mode" : "000644",
"owner" : "root",
"group" : "root",
"authentication" : "S3AccessCreds"
},
"/etc/chef/client.rb" : {
"content" : { "Fn::Join" : ["", [
"log_level :infon",
"log_location STDOUTn",
"ssl_verify_mode :verify_nonen",
"chef_server_url 'https://chef-server.nclouds.net'n",
"environment '", { "Ref" : "ChefEnvironment" }, "'n",
"validation_client_name 'chef-validator'n"
]]},
"mode" : "000644",
"owner" : "root",
"group" : "root"
},
"/etc/chef/roles.json" : {
"content" : { "Fn::Join" : ["", [
"{"run_list": [ "role[base]","role[",{ "Ref" : "ChefRole" },"]" ]}"
]]},
"mode" : "000644",
"owner" : "root",
"group" : "root"
}
},
"services" : {
},
"users" : {
},
"groups" : {
}
}
},
"AWS::CloudFormation::Authentication" : {
"S3AccessCreds" : {
"type" : "S3",
"accessKeyId" : { "Ref" : "AccessKey" },
"secretKey" : { "Ref" : "SecretKey"}
}
}
},
"Properties" : {
"InstanceType" : { "Ref" : "InstanceType" },
"KeyName" : {"Ref" : "KeyName"},
"UserData" : {
"Fn::Base64" : {
"Fn::Join" : [ "", [
"#!/bin/bash -vn",
"curl -L https://www.opscode.com/chef/install.sh | bashn",
"echo '54.214.7.132 chef-server.nclouds.net' >> /etc/hostsn",
"yum update -y aws-cfn-bootstrapn",
"/opt/aws/bin/cfn-init -s ", { "Ref" : "AWS::StackName" }, " -r LaunchConfig",
" --access-key ", { "Ref" : "AccessKey" },
" --secret-key ", { "Ref" : "SecretKey" },
" --region ", { "Ref" : "AWS::Region" }, "|| error_exit 'Failed to run cfn-init'n",
"LOCAL_IP=`curl -s https://169.254.169.254/latest/meta-data/local-ipv4 | sed 's/./-/g'`n",
"echo "node_name "",{ "Ref" : "AWS::StackName" },"-$LOCAL_IP"" >> /etc/chef/client.rbn",
"chef-client -S https://chef-server.nclouds.net -j /etc/chef/roles.json -N ", { "Ref" : "AWS::StackName" }, "-`echo -n $LOCAL_IP` -E ", { "Ref" : "ChefEnvironment" }, ""
]
]
}
},
"ImageId" : {"Ref" : "TomcatAmi"},
"SecurityGroups" : [{ "Ref" : "SecurityGroup" }]
}
}
}
}
