Split Up / Include / Reference external configuration in Serverless Framework file

Using Serverless Framework ${file()} variable to load external files into serverless.yml.

service: serverless-framework-include-files
frameworkVersion: "3"

provider: ${file(config/provider.yml):provider}

functions:
  function1:
    handler: index.handler

resources:
  - ${file(resources/s3-bucket.yml)}
  - ${file(resources/dynamodb-table.yml)}

How does `provider: ${file(config/provider.yml):provider}` works?

The variable ${file(...):<key-name>} use the key-name as the property key in the external file to be included in the serverless.yml file. Make sure the key name exists in the external file with a colon <key-name>:. In this example we are looking for the provider key in the config/provider.yml file:

provider: # <--- key name, it will load the properties of the key name as configuration
  name: aws
  runtime: nodejs14.x

You can include the whole file by removing the key name: ${file(...)}. Make sure the external file contains the correct configuration for target property in the serverless.yml file.

# no key name, it will load the whole file as configuration values in the serverless.yml file
name: aws
runtime: nodejs14.x

How does `resources:` works?

The serverless.yml file supports multiple ways to declare AWS resources. These resources use the CloudFormation Resources syntax.

resources:
  Resources:
    # <--- Declare any AWS resources here

You can declare AWS resources inline, include external files with the resources configuration or use the array syntax to mix inline and external files.

1) AWS resources inline

resources:
  Resources:
    MyBucket:
      Type: AWS::S3::Bucket
      Properties:
        BucketName: my-bucket
    MyTable:
      Type: AWS::DynamoDB::Table
      Properties:
        TableName: my-table
        AttributeDefinitions:
          - AttributeName: id
            AttributeType: S
        KeySchema:
          - AttributeName: id
            KeyType: HASH
        ProvisionedThroughput:
          ReadCapacityUnits: 1
          WriteCapacityUnits: 1

2) AWS resources configuration in external files

Make sure the contents of your external file match the configuration of the AWS resource.

resources:
  Resources:
    MyBucket: ${file(resources/s3-bucket2.yml)}
    MyTable: ${file(resources/dynamodb-table2.yml)}

The resources/s3-bucket2.yml file:

Type: AWS::S3::Bucket
Properties:
  BucketName: my-bucket
  AccessControl: PublicRead
  WebsiteConfiguration:
    IndexDocument: index.html
    ErrorDocument: error.html

3) Load AWS resources in external files

Make sure your external files are declaring/start with the Resources: key.

resources:
  - ${file(resources/s3-bucket.yml)}
  - ${file(resources/dynamodb-table.yml)}

The resources/s3-bucket2.yml file:

Resources: # <--- required CloudFormation syntax
  MyBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: my-bucket
      AccessControl: PublicRead
      WebsiteConfiguration:
        IndexDocument: index.html
        ErrorDocument: error.html

4) Inline and external files with AWS resources

The secret sauce is the Resources: key. It allows you to mix inline and external files.

resources:
  - ${file(resources/s3-bucket.yml)}
  - Resources:
      MyBucket: ${file(resources/s3-bucket2.yml)}
  - Resources:
      MyTable:
        Type: AWS::DynamoDB::Table
        Properties:
          TableName: ${self:service}
          AttributeDefinitions:
            - AttributeName: id
              AttributeType: S
          KeySchema:
            - AttributeName: id
              KeyType: HASH
          ProvisionedThroughput:
            ReadCapacityUnits: 1
            WriteCapacityUnits: 1

oieduardorabelo/serverless-framework-include-files