Reuse an Existing API Gateway Stage

Generic setup

provider:
  name: aws
  runtime: nodejs12.x
  stage: ${opt:stage, "dev"}
  region: ${opt:region, "us-east-1"}
  apiGateway:
    restApiId: ${self:custom.restApiId}
    restApiRootResourceId: ${self:custom.restApiRootResourceId}
custom:
  restApiId: xyz # <-- Add your existing API Gateway REST API ID
  restApiRootResourceId: xyz # <-- Add your existing API Gateway REST API Root Resource ID (e.g. path of / id)
  restApiStageName: existing  # <-- change to your existing deployment stage name
functions:
  hello:
    handler: handler.hello
    events:
      - http:
          path: /hello
          method: GET
resources:
  Resources:
    StageDeployment:
      DependsOn: ApiGatewayMethodHelloGet  # <-- replace based on your function method name which is created by serverless framework (found by searching for "ApiGatewayMethod" in .serverless/ folder)
      Type: AWS::ApiGateway::Deployment
      Properties:
        RestApiId: ${self:custom.restApiId}
        Description: Reuse ${self:custom.restApiStageName} deployment
        StageName: ${self:custom.restApiStageName}

Key changes to note

• The stage name is defined in the custom block - self:custom.restApiStageName
• The Stage deployment is defined as a new CloudFormation resource.
  • DependsOn refers to both the function and the http method. Is based on your function method name which is created by serverless framework, and can be found by searching for "ApiGatewayMethod" in .serverless/ folder.
  • The RestApiID is the same that is defined in the custom block.
  • StageName is defined in the custom block as well, but takes a string.

Deploying with this in place will add the applicable function methods to the stage you define.