@mapbox/magic-cfn-resources

magic-cfn-resources

Builds Lambda-backed custom Cloudformation resources. When you use magic-cfn-resources's build method, a Lambda function is created in your stack and used to build a custom resource. Resources that can be built with magic-cfn-resources are: SnsSubscription, DynamoDBStreamLabel, StackOutputs, and SpotFleet.

Provided resources in detail:

SNS Subscriptions

This allows you to manage SNS subscriptions as though they are first-class CloudFormation resources.

DynamoDB Stream Labels

This does not actually create any backend resource, but looks up the label for the stream associated with a DynamoDB table.

This resource will use the stream's label as its PhysicalResourceId, so you can then access the label itself in your template via:

{ "Ref": "LogicalNameOfYourCustomResource" }

CloudFormation StackOutputs

Looks up the Outputs for an existing CloudFormation stack.

You can access the values of the stack's outputs with Fn::GetAtt

{ "Fn::GetAtt": ["LogicalNameOfYourCustomResource", "LogicalNameOfStackOutput"] }

SpotFleet

Makes SpotFleet requests.

DefaultVpc

Looks up the default VPC in the region you've launched your stack in, and provides information about the VPC via Fn::GetAtt.

{ "Fn::GetAtt": ["LogicalNameOfYourCustomResource", "VpcId"] }

You can use Fn::GetAtt to obtain the following data:

• VpcId: the default VPC's ID
• AvailabilityZones: an array of strings representing the VPC's availability zones
• AvailabilityZoneCount: the number of availability zones
• PublicSubnets: an array of strings representing the VPC's public subnets
• RouteTable: the ID for the first route table in the VPC

To create a magical resource in your own CloudFormation template:

In an existing script or in a new script (i.e. sns-subscription.js):

// Purpose: create a handler for your Lambda function to reference

const magicCfnResources = require('@mapbox/magic-cfn-resources');
// export the custom function needed for your stack.
module.exports.SnsSubscription = magicCfnResources.SnsSubscription;

Another example: module.exports.SpotFleet = magicCfnResources.SpotFleet;

In the CloudFormation template of your stack:

const magicCfnResources = require('@mapbox/magic-cfn-resources');

Then, pass in the necessary parameters to magicCfnResources.build. These are the parameters needed for each resource:

SnsSubscription

const SnsSubscription = magicCfnResources.build({
  CustomResourceName: 'SnsSubscription',
  LogicalName: 'Logical Name', // a name to refer to the custom resource being built
  S3Bucket: 'Bucket Name', // the S3 bucket the code for the handler lives in
  S3Key: 'Key', // the S3 key for where the handler lives
  Handler: 'sns-subscription.SnsSubscription', // references the handler created in the repository
  Properties: {
    SnsTopicArn: 'Topic Arn', // the ARN of the SNS Topic you are subscribing to
    Protocol: 'Protocol', // the SNS protocol, i.e. 'sqs', 'email'
    Endpoint: 'Endpoint' // the endpoint you are subscribing
  }
});

DynamoDBStreamLabel

const DynamoDBStreamLabel = magicCfnResources.build({
  CustomResourcenName: 'DynamoDBStreamLabel',
  LogicalName: 'Logical Name', // a name to refer to the custom resource being built
  S3Bucket: 'Bucket Name', // the S3 bucket the code for the handler lives in
  S3Key: 'Key', // the S3 key for where the handler lives
  Handler: 'dynamodb-stream-label.DynamoDBStreamLabel', // references the handler created in the repository
  Properties: {
    TableName: 'Name of Table', // the name of the DynamoDB table
    TableRegion: 'Region' // the region of the DynamoDB table i.e.: 'us-east-1'
  }
});

StackOutputs

const StackOutputs = magicCfnResources.build({
  CustomResourceName: 'StackOutputs',
  LogicalName: 'Logical Name', // a name to refer to the custom resource being built
  S3Bucket: 'Bucket Name', // the S3 bucket the code for the handler lives in
  S3Key: 'Key', // the S3 key for where the handler lives
  Handler: 'stack-outputs.StackOutputs', // references the handler created in the repository
  Properties: {
    StackName: 'Name', // name of the CloudFormation stack
    StackRegion: 'region' // region of the CloudFormation stack i.e.: 'us-east-1'
  }
});

SpotFleet

const SpotFleet = magicCfnResources.build({
  CustomResourceName: 'SpotFleet',
  LogicalName: 'Logical Name', // a name to refer to the custom resource being built
  S3Bucket: 'Bucket Name', // the S3 bucket the code for the handler lives in
  S3Key: 'Key', // the S3 key for where the handler lives
  Handler: 'spot-fleet.SpotFleet', // references the handler created in the repository
  Properties: {
    SpotFleetRequestConfigData: { }, // object with SpotFleet configuration specifics
    Region: 'region', // region of the SpotFleet i.e.: 'us-east-1'
  }
});

DefaultVpc

const DefaultVpd = magicCfnResources.build({
  CustomResourceName: 'DefaultVpc',
  LogicalName: 'Logical Name', // a name to refer to the custom resource being built
  S3Bucket: 'Bucket Name', // the S3 bucket the code for the handler lives in
  S3Key: 'Key', // the S3 key for where the handler lives
  Handler: 'index.DefaultVpc', // references the handler created in the repository
  Properties: {}
});

Optional Condition

A Condition from your template can also be passed into build. i.e.:

const SpotFleet = magicCfnResources.build({
  CustomResourceName: 'SpotFleet',
  LogicalName: 'Logical Name', // a name to refer to the custom resource being built
  S3Bucket: 'Bucket Name', // the S3 bucket the code for the handler lives in
  S3Key: 'Key', // the S3 key for where the handler lives
  Handler: 'spot-fleet.SpotFleet', // references the handler created in the repository
  Properties: {
    SpotFleetRequestConfigData: { }, // object with SpotFleet configuration specifics
    Region: 'region', // region of the SpotFleet i.e.: 'us-east-1'
  },
  Condition: 'Condition' // the Logical ID of a condition
});

Merge the resources created with build with the resources already in the stack's template:. i.e.:

const cloudfriend = require('@mapbox/cloudfriend');
const magicCfnResources = require('@mapbox/magic-cfn-resources');

module.exports = cloudfriend.merge(SnsSubscription, <Stack Resources>);

To build new functions

Check out contributing.md for a discussion of the framework this library provides for writing other functions.