Better way to tag Instances

[cfndsl]

Better way to tag Instances

[howech]

It turns out that for resource types that declare a Tags property, the Tag method gets defined automagically by the part that generates the various resource subclasses. Currently, only EC2::Instance, EC2::Volume and AutoScaling::AutoScalingGroup declare that they have a "Tags" property - cloudformation might now support some other resources that have tags.

To use the existing autogenerated functions you can do things like this:

Instance("Myinstance") {
  Tag {
    Key "Name"
    Value "MyInstance"
   }
  Tag {
    Key "Custom"
    Value "Blah blah bla"
   }
}

AutoScalingGroup("MyGroup") {
  Tag {
    Key "Name"
    Value "MyGroup"
    PropagateAtLaunch true
  }
  Tag {
    Key "Custom"
    Value "Blah blah bla"
    PropagateAtLaunch false
   }
}

This will generate an instance and an autoscaling group, each with two tags. One of the autoscaling group's tags will propagate to its instances, the other will not.

In cfndsl version 0.0.12, I added a function to the Resource class (ResourceDefintion) called addTag. It basically tries to call the Tag function if it is around, and only passes the PropagateAtLaunch if it is given.

Instance("Myinstance") {
  addTag( "Name", "MyInstance" )
  addTag( "Custom", "Blah blah blah")
}

AutoScalingGroup("MyGroup") {
  addTag( "Name", "MyGroup", true )
  addTag( "Custom", "Blah blah blah", false)
}

If you try to addTag to some resource that does not have a Tags property, cfndsl will fail trying to build the template.

[liguorien]

Thank you very much!

[josh-wrale]

This isn't working right now. If I add an addTag to an AWS::EC2::VPC resource, I get:

vagrant@vagrant-ubuntu-precise-64:/devops/assets/cfndsl/reference$ cfndsl reusable-vpc.rb
/var/lib/gems/1.9.1/gems/cfndsl-0.0.16/lib/cfndsl/Resources.rb:13: Undefined symbol: Tag()
/var/lib/gems/1.9.1/gems/cfndsl-0.0.16/lib/cfndsl/Resources.rb:13: Undefined symbol: Tag()
/var/lib/gems/1.9.1/gems/cfndsl-0.0.16/lib/cfndsl/Resources.rb:13: Undefined symbol: Tag()
vagrant@vagrant-ubuntu-precise-64:/devops/assets/cfndsl/reference$

Perhaps, I'm doing something wrong?

[josh-wrale]

Alright, so the issue is that the addTag approach doesn't work when structuring a VPC resource as follows:

This doesn't work:

  Resource("VPC" ) {
    Type "AWS::EC2::VPC"
    Property( "CidrBlock", Ref("VpcCidrBlock" )  ) 
    Property( "InstanceTenancy", Ref("VpcInstanceTenancy" ) )
    addTag( "Name", "Test")
  }

You must do this, whose syntax I incidentally like better:

  VPC("VPC") {
    CidrBlock Ref( "VpcCidrBlock" )
    InstanceTenancy Ref( "VpcInstanceTenancy" )
    addTag("Name", "Test")
  }

Awesome... I think the readme file led me into this trap. Please advise.

Thanks for this amazing tool!

-Joshua