AWS Cloudformation Diagramming Shortcut

A quick little shortcut if you want a visualization of your Cloudformation stack…

  1. Log into the AWS console and go to Cloudformation.
  2. Click DESIGN TEMPLATE
  3. At the bottom of the screen look for the TEMPLATE tab.
  4. Copy your CF template you are working on and paste it in here. Make sure you are overwriting the prefilled JSON thats already there.
  5. In the upper right hand corner look for the Refresh button. It looks like 2 arrows going in a circle.
  6. Now you should see your CF stack visualized. Now you can click the Export button that is near the refresh button you just used.

 

Setting up an Apache server using AWS CloudFormation

This a is a brief and simple guide to spinning up an instance, installing Apache, and writing output to a webpage.

Note that by following this guide you can incur charges. Im not responsible for them and will not be picking up your bill.

Setup

1. Have an AWS account. You can signup for one here: http://aws.amazon.com/
2. Have a computer you can work from. This guide assumes you are running Linux. What other OS is there anyways? For me I have an instance on AWS that I startup whenever I want to work on stuff. On this computer you need to install the AWS CLI tool. You can install and setup the CLI tool by going here: http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-set-up.html
3. Basic understanding of JSON…not a requirement but it helps to understand what you are reading in the template.

The Template

First here is a link that will guide you further than im going to here on the ins and outs of templates and requirements for CloudFormation: http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-guide.html

So lets break down the template…

{
 "AWSTemplateFormatVersion" : "2010-09-09",

This is an optional but lets AWS know what version of the template you are using. This is NOT today’s date or something.

"Description" : "Create an Apache webserver with a webpage.",

Gives a description of what your template is for.

"Parameters" : {
    "InstanceType" : {
      "Description" : "Type of EC2 instance to launch",
      "Type" : "String",
      "Default" : "t1.micro"
    },
    "WebServerPort" : {
      "Description" : "TCP/IP port of the web server",
      "Type" : "String",
      "Default" : "80"
    },
    "KeyName" : {
      "Description" : "Name of an existing EC2 KeyPair to enable SSH access to the instances",
      "Type" : "AWS::EC2::KeyPair::KeyName",
      "ConstraintDescription" : "must be the name of an existing EC2 KeyPair."
    },
    "SSHLocation": {
            "Description": " The IP address range that can be used to SSH to the EC2 instances",
            "Type": "String",
            "MinLength": "9",
            "MaxLength": "18",
            "Default": "0.0.0.0/0",
            "AllowedPattern": "(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})/(\\d{1,2})",
            "ConstraintDescription": "must be a valid IP CIDR range of the form x.x.x.x/x."
        }
  },

Breaking down the parameters directive…
*If you dont give your parameter a “Default” you will need to pass in the option via the command line. This will be explained further but keep that in mind in this section.
InstanceType – Tells what kind you want to launch. The default here is t1.micro.
WebServerPort – You are telling what port your webserver will accept connections on.
KeyName – This is the name of your AWS key that you use to authenticate with. Use a key that has permissions to setup new instances and connect to them.
SSHLocation – The IP address range that can be used to SSH to the EC2 instances

"Mappings" : {
    "AWSInstanceType2Arch" : {
      "t1.micro"    : { "Arch" : "64" }
    },
    "AWSRegionArch2AMI" : {
      "us-east-1"          : { "64" : "ami-246ed34c" }
    }
  },

Mappings…tells what region and what AMI you want to use. For brevity I already knew what I wanted to use and that I wanted it to fail if not available so my listing of types and regions is VERY short. You can see further info here on mappings: http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/mappings-section-structure.html

Now we will talk about the Resources section. Its where all the real magic happens. Ill break it down some and then provide the full section at the bottom of this page.

"Resources" : {     
      
    "WebServerInstance": {  
      "Type": "AWS::EC2::Instance",
      "Metadata" : {
        "AWS::CloudFormation::Init" : {
          "configSets" : {
            "InstallAndRun" : [ "Install" ]
          },

          "Install" : {
            "packages" : {
              "yum" : {
                "httpd"        : []              
              }
            },

Here, we are saying that we want to initialize and install something on our instance. Notice that we are using “yum”. The AMI I use is an Amazon AMI which is RHEL based. It comes with some tools already setup and installed specific to AWS so its easier to use this AMI base. Here all we are installing is Apache, or “httpd”.

"files" : {
              "/var/www/html/index.html" : {
              "source" : "https://s3.amazonaws.com/BUCKET_NAME/index.html",  
              "mode"  : "000600",
              "owner" : "apache",
              "group" : "apache"
              },

              "/etc/cfn/cfn-hup.conf" : {
                "content" : { "Fn::Join" : ["", [
                  "[main]\n",
                  "stack=", { "Ref" : "AWS::StackId" }, "\n",
                  "region=", { "Ref" : "AWS::Region" }, "\n"
                ]]},
                "mode"    : "000400",
                "owner"   : "root",
                "group"   : "root"
              },

Here we are pulling down our simple html file from our S3 bucket. I could have easily added code here that would have written to the file the HTML code. Its just cleaner looking code wise to simply pull down the file from your bucket. We are also setting the conf file for cfn-hup. That’s a helper daemon that detects changes and reacts when you are making updates to your stack.

"/etc/cfn/hooks.d/cfn-auto-reloader.conf" : {
                "content": { "Fn::Join" : ["", [
                  "[cfn-auto-reloader-hook]\n",
                  "triggers=post.update\n",
                  "path=Resources.WebServerInstance.Metadata.AWS::CloudFormation::Init\n",
                  "action=/opt/aws/bin/cfn-init -v ",
                  "         --stack ", { "Ref" : "AWS::StackName" },
                  "         --resource WebServerInstance ",
                  "         --configsets InstallAndRun ",
                  "         --region ", { "Ref" : "AWS::Region" }, "\n",
                  "runas=root\n"
                ]]}
              }
            },
            "services" : {
              "sysvinit" : {  
                "httpd"   : { "enabled" : "true", "ensureRunning" : "true" },
                "cfn-hup" : { "enabled" : "true", "ensureRunning" : "true",
                              "files" : ["/etc/cfn/cfn-hup.conf", "/etc/cfn/hooks.d/cfn-auto-reloader.conf"]}}}}}
},

More cfn helper to manage changes. Also see that we are enabling and making sure that httpd and cfn-hup are running on startup. This could also be done through scripting placed into the template.

"Properties": {
        "ImageId" : { "Fn::FindInMap" : [ "AWSRegionArch2AMI", { "Ref" : "AWS::Region" },
                          { "Fn::FindInMap" : [ "AWSInstanceType2Arch", { "Ref" : "InstanceType" }, "Arch" ] } ] },
        "InstanceType"   : { "Ref" : "InstanceType" },
        "SecurityGroups" : [ {"Ref" : "WebServerSecurityGroup"} ],
        "KeyName"        : { "Ref" : "KeyName" },
        "UserData"       : { "Fn::Base64" : { "Fn::Join" : ["", [
             "#!/bin/bash -xe\n",
             "yum update -y aws-cfn-bootstrap\n",

             "# Install the files and packages from the metadata\n",
             "/opt/aws/bin/cfn-init -v ",
             "         --stack ", { "Ref" : "AWS::StackName" },
             "         --resource WebServerInstance ",
             "         --configsets InstallAndRun ",
             "         --region ", { "Ref" : "AWS::Region" }, "\n",

             "# Signal the status from cfn-init\n",
             "/opt/aws/bin/cfn-signal -e $? ",
             "         --stack ", { "Ref" : "AWS::StackName" },
             "         --resource WebServerInstance ",
             "         --region ", { "Ref" : "AWS::Region" }, "\n"]]}}}
},

Properties for the instance…Calling on the Mappings info and the yet to be mentioned SecurityGroup. This is also where the packages are installed and configured as you can see the scripting here. Also note that this has all been part of “WebServerInstance”. We are just ending that section.

"WebServerSecurityGroup" : {
      "Type" : "AWS::EC2::SecurityGroup",
      "Properties" : {
        "GroupDescription" : "Enable HTTP access via port 80",
        "SecurityGroupIngress" : [
          {"IpProtocol" : "tcp", "FromPort" : "80", "ToPort" : "80", "CidrIp" : "0.0.0.0/0"},
          {"IpProtocol" : "tcp", "FromPort" : "22", "ToPort" : "22", "CidrIp" : { "Ref" : "SSHLocation"}}
        ]
      }
    }
  },

This sets up the security group and allows access to ports 22 and 80 for http and ssh traffic.

"Outputs" : {
    "WebsiteURL" : {
      "Description" : "URL for newly created Apache server",
      "Value" : { "Fn::Join" : ["", ["http://", { "Fn::GetAtt" : [ "WebServerInstance", "PublicDnsName" ]}]] }
    }
  }
}

This section will output the info you need to know the URL of your new instance. You will look in the Output section of your CloudFormation stack to see the info which will be a link you can click to see your webpage.

AWS Command

So now you have your AWS CLI tool installed and you have your template written…now its time to fire up your stack and see the fruits of your labor.

The command you will want to run is:

aws cloudformation create-stack --stack-name STACK_NAME --template-url https://s3.amazonaws.com/BUCKET_NAME/template.json --parameters  ParameterKey=KeyName,ParameterValue=YOUR_KEY_NAME

This declares that you are using cloudformation to create a new stack, you are giving the stack name, location of where you will download and read the template from, and finally filling in the parameter of your AWS key.
*Remember earlier when I said that if you do not have a “default” for a parameter that you will need to provide it? This is where I was talking about. For the KeyName param we did not provide a default keyname to use. You can pass a number of parameters on the command line as we have here up to a maximum of 60. Really at that point you should be looking at a scripted option to provide those right?

So once you have executed the above command you can look in your CloudFormation and see your stack being created. If it fails it will stop and rollback the creation. Once it completes go to your Output tab and you should see the URL of your webpage. Click it and you should see whatever you put in your index.html file that is in your S3 bucket.

That’s about it. The best way to learn this is to play around with it and read through the CloudFormation documentation. Let me know if you have comments or questions.

 

Full template for you to copy and paste:

Make sure you use a json validator to be sure that the copy and paste didn’t mangle anything.
{
  "AWSTemplateFormatVersion" : "2010-09-09",

  "Description" : "Create an Apache webserver with a webpage.",

  "Parameters" : {
    "InstanceType" : {
      "Description" : "Type of EC2 instance to launch",
      "Type" : "String",
      "Default" : "t1.micro"
    },
    "WebServerPort" : {
      "Description" : "TCP/IP port of the web server",
      "Type" : "String",
      "Default" : "80"
    },
    "KeyName" : {
      "Description" : "Name of an existing EC2 KeyPair to enable SSH access to the instances",
      "Type" : "AWS::EC2::KeyPair::KeyName",
      "ConstraintDescription" : "must be the name of an existing EC2 KeyPair."
    },
    "SSHLocation": {
            "Description": " The IP address range that can be used to SSH to the EC2 instances",
            "Type": "String",
            "MinLength": "9",
            "MaxLength": "18",
            "Default": "0.0.0.0/0",
            "AllowedPattern": "(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})/(\\d{1,2})",
            "ConstraintDescription": "must be a valid IP CIDR range of the form x.x.x.x/x."
        }
  },

  "Mappings" : {
    "AWSInstanceType2Arch" : {
      "t1.micro"    : { "Arch" : "64" }
    },
    "AWSRegionArch2AMI" : {
      "us-east-1"          : { "64" : "ami-246ed34c" }
    }
  },

"Resources" : {     
      
    "WebServerInstance": {  
      "Type": "AWS::EC2::Instance",
      "Metadata" : {
        "AWS::CloudFormation::Init" : {
          "configSets" : {
            "InstallAndRun" : [ "Install" ]
          },

          "Install" : {
            "packages" : {
              "yum" : {
                "httpd"        : []              
              }
            },

            "files" : {
              "/var/www/html/index.html" : {
              "source" : "https://s3.amazonaws.com/BUCKET_NAME/index.html",  
              "mode"  : "000600",
              "owner" : "apache",
              "group" : "apache"
              },

              "/etc/cfn/cfn-hup.conf" : {
                "content" : { "Fn::Join" : ["", [
                  "[main]\n",
                  "stack=", { "Ref" : "AWS::StackId" }, "\n",
                  "region=", { "Ref" : "AWS::Region" }, "\n"
                ]]},
                "mode"    : "000400",
                "owner"   : "root",
                "group"   : "root"
              },

              "/etc/cfn/hooks.d/cfn-auto-reloader.conf" : {
                "content": { "Fn::Join" : ["", [
                  "[cfn-auto-reloader-hook]\n",
                  "triggers=post.update\n",
                  "path=Resources.WebServerInstance.Metadata.AWS::CloudFormation::Init\n",
                  "action=/opt/aws/bin/cfn-init -v ",
                  "         --stack ", { "Ref" : "AWS::StackName" },
                  "         --resource WebServerInstance ",
                  "         --configsets InstallAndRun ",
                  "         --region ", { "Ref" : "AWS::Region" }, "\n",
                  "runas=root\n"
                ]]}
              }
            },

            "services" : {
              "sysvinit" : {  
                "httpd"   : { "enabled" : "true", "ensureRunning" : "true" },
                "cfn-hup" : { "enabled" : "true", "ensureRunning" : "true",
                              "files" : ["/etc/cfn/cfn-hup.conf", "/etc/cfn/hooks.d/cfn-auto-reloader.conf"]}
              }
            }
          }

        }
      },
      "Properties": {
        "ImageId" : { "Fn::FindInMap" : [ "AWSRegionArch2AMI", { "Ref" : "AWS::Region" },
                          { "Fn::FindInMap" : [ "AWSInstanceType2Arch", { "Ref" : "InstanceType" }, "Arch" ] } ] },
        "InstanceType"   : { "Ref" : "InstanceType" },
        "SecurityGroups" : [ {"Ref" : "WebServerSecurityGroup"} ],
        "KeyName"        : { "Ref" : "KeyName" },
        "UserData"       : { "Fn::Base64" : { "Fn::Join" : ["", [
             "#!/bin/bash -xe\n",
             "yum update -y aws-cfn-bootstrap\n",

             "# Install the files and packages from the metadata\n",
             "/opt/aws/bin/cfn-init -v ",
             "         --stack ", { "Ref" : "AWS::StackName" },
             "         --resource WebServerInstance ",
             "         --configsets InstallAndRun ",
             "         --region ", { "Ref" : "AWS::Region" }, "\n",

             "# Signal the status from cfn-init\n",
             "/opt/aws/bin/cfn-signal -e $? ",
             "         --stack ", { "Ref" : "AWS::StackName" },
             "         --resource WebServerInstance ",
             "         --region ", { "Ref" : "AWS::Region" }, "\n"
        ]]}}        
      }
    },
    
    "WebServerSecurityGroup" : {
      "Type" : "AWS::EC2::SecurityGroup",
      "Properties" : {
        "GroupDescription" : "Enable HTTP access via port 80",
        "SecurityGroupIngress" : [
          {"IpProtocol" : "tcp", "FromPort" : "80", "ToPort" : "80", "CidrIp" : "0.0.0.0/0"},
          {"IpProtocol" : "tcp", "FromPort" : "22", "ToPort" : "22", "CidrIp" : { "Ref" : "SSHLocation"}}
        ]
      }
    }
  },
  
  "Outputs" : {
    "WebsiteURL" : {
      "Description" : "URL for newly created Apache server",
      "Value" : { "Fn::Join" : ["", ["http://", { "Fn::GetAtt" : [ "WebServerInstance", "PublicDnsName" ]}]] }
    }
  }
}