SQS::Worker::CloudFormationResource - A helper to develop your own custom CloudFormation resources

This is a SQS::Worker role that helps you develop SNS-based CloudFormation Custom Resources that deliver to an SQS queue.

More information on SNS based Custom Resources here: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-custom-resources-sns.html

This module takes care of lots of repetitive work when building an SNS-based CloudFormation Custom Resource.

package MyCustomResource {
  use Moose;
  with 'SQS::Worker', 'SQS::Worker::SNS', 'SQS::Worker::CloudFormationResource';

  sub create_resource {
    my ($self, $request, $result) = @_;
    # $request is a SQS::Worker::CloudFormationResource::Request
    # $result  is a SQS::Worker::CloudFormationResource::Response
  }

  sub update_resource {
    my ($self, $request, $result) = @_;
  }

  sub delete_resource {
    my ($self, $request, $result) = @_;
  }
}

The worker will poll the SQS queue for you, invoking create_resource, update_resource or delete_resource in function of what is happening in CloudFormation, passing them a request object with all the information coming from CloudFormation. Look at SQS::Worker::CloudFormationResource::Request for more information on what information a request has. result is an object that has SQS::Worker::CloudFormationResource::Response. Set the appropiate properties of the response object. The response object will be returned to CloudFormation.

$result->set_success('Created resource'); # the success message will show in the cloudformation log
$result->PhysicalResourceId('resource-123456');
$result->Data({
  Color => 'Blue',
});

When calling update_resource: PhysicalResourceId will already be initialized to the PhisicalResourceId that was set in create_resource, meaning that if it isn't updated, CloudFormation considers the update as a in-place replacement. If a new PhysicalResourceId is assigned, CloudFormation considers the operation as a replacement. Later on, CloudFormation will send a Delete for the old PhysicalResourceId, which shouldn't be handled as any special case: the delete_resource will be invoked.

Unhandled exceptions in any resource_* methods will be handled, returning a generic "Internal Error" text to CloudFormation, considering the resource FAILED.

Unhandled exceptions in resource_create will treat the resource creation as a special case. Since CloudFormation requires a Physical ID to be sent, even if we're signalling a FAILURE, SQS::Worker::CloudFormationResource will use an internal Physical ID, that will never be delivered to the delete_resource method (it will be intercepted and dropped before getting processed).

To use the resource in CloudFormation, you have to provision an SNS topic that delivers it's messages to an SQS queue. You can setup an SNS topic with the bundled examples/sns-topic-for-cloudformation.json file (which will output all the data you need to run the worker

spawn_worker --worker CustomResourceExample1 --queue_url=http://..../QueueURL --region=eu-west-1 --log_conf log.conf

{ "resources": [
  "Custom1": {
    "Type": "Custom::MyCustomResource",
    "Version": "1.0",
    "Properties": {
      "ServiceToken": "arn:of the SNS topic for the custom resource",
      ... Resource Properties ...
    }
  }
] }

The data you have set in the Data property of the response object will be accessible in CloudFormation templates via the GetAtt function.

{ "Fn::GetAtt": [ "Custom1", "Color" ] }

Implement this method in your Custom Resource worker class. All properties sent by CloudFormation will be in $request of type SQS::Worker::CloudFormationResource::Request. This method should modify $response to control what will be sent to CloudFormation. The following can be done:

Either call set_success or set_failed

Set attribute PhysicalResourceId ($response->('resource-123456');)

Set attribute Data to a Hashref with the keys and values that CloudFormation will treat as this objects attributes

Implement this method in your Custom Resource worker class.

Implement this method in your Custom Resource worker class.

Either call set_success or set_failed to indicate that the resource was deleted or not

SQS::Worker

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-custom-resources-sns.html

Paws::SQS

Copyright (c) 2018 by CAPSiDE

This code is distributed under the Apache 2 License. The full text of the license can be found in the LICENSE file included with this module.

Jose Luis Martinez
JLMARTIN
[email protected]