TWagnerMediumBlogSampleCFTemplatePart8

MediumCFArticle8.yaml

  # The top-level websocket itself
  NATPunchWebSocket:
    Type: AWS::ApiGatewayV2::Api
    Properties:
      Name: NATPunchWebSocket
      ProtocolType: WEBSOCKET
      RouteSelectionExpression: "$request.body.action"

  # The builtin $connect path. This involves both a route
  # definition and its integration definition, which follows, as well as a 
  # synchronous response from the Lambda proxy that returns success/failure info to the caller.
  NATPunchConnectRoute:
    Type: AWS::ApiGatewayV2::Route
    Properties:
      ApiId: !Ref NATPunchWebSocket
      RouteKey: $connect
      AuthorizationType: NONE
      OperationName: NATPunchConnectRoute
      # A Lambda proxy response is used for $connect messages to return
      # success/failure info to the caller.
      # See the matching response section following the integration definition.
      RouteResponseSelectionExpression: $default
      Target: !Join ['/', [integrations, !Ref NATPunchConnectInteg]] # See below

  # The Lambda proxy for $connect.
  NATPunchConnectInteg:
    Type: AWS::ApiGatewayV2::Integration
    Properties:
      ApiId: !Ref NATPunchWebSocket
      Description: Integration for builtin $connect route
      IntegrationType: AWS_PROXY
      # All routes lead to the same Lambda function; it uses the route
      # provided by API Gateway to determine the right behavior.
      IntegrationUri:
        !Sub arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${NATPunchFunction.Arn}/invocations

  # The Lambda proxy response to $connect, which returns success/failure info to the caller.
  NATPunchConnectRouteResponse:
    Type: 'AWS::ApiGatewayV2::RouteResponse'
    Properties:
      RouteId: !Ref NATPunchConnectRoute
      ApiId: !Ref NATPunchWebSocket
      RouteResponseKey: $default

  # The builtin $disconnect path. This involves both a route
  # definition and its integration definition, which follows, as well as a 
  # synchronous response from the Lambda proxy.
  NATPunchDisconnectRoute:
    Type: AWS::ApiGatewayV2::Route
    Properties:
      ApiId: !Ref NATPunchWebSocket
      RouteKey: $disconnect
      AuthorizationType: NONE
      OperationName: NATPunchDisconnectRoute
      # A Lambda proxy response is used for $disconnect messages to return
      # success/failure info to the caller.
      # See the matching response section following the integration definition.
      RouteResponseSelectionExpression: $default
      Target: !Join ['/', [integrations, !Ref NATPunchDisconnectInteg]]
 
  # The Lambda proxy for $disconnect.
  NATPunchDisconnectInteg:
    Type: AWS::ApiGatewayV2::Integration
    Properties:
      ApiId: !Ref NATPunchWebSocket
      Description: Integration for builtin $disconnect route
      IntegrationType: AWS_PROXY
      # All routes lead to the same Lambda function; it uses the route
      # provided by API Gateway to determine the right behavior.
      IntegrationUri:
        !Sub arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${NATPunchFunction.Arn}/invocations

  # The Lambda proxy response to $disconnect, which returns success/failure info to the caller.
  NATPunchDisconnectRouteResponse:
    Type: 'AWS::ApiGatewayV2::RouteResponse'
    Properties:
      RouteId: !Ref NATPunchDisconnectRoute
      ApiId: !Ref NATPunchWebSocket
      RouteResponseKey: $default

  # The builtin $default path. This involves both a route
  # definition and its integration definition, which follows, as well as a 
  # synchronous response from the Lambda proxy.
  # The NATPunch websocket does *not* rely on the $default route for anything constructive;
  # any calls it are, by definition, errors and return a "malformed request" argument.
  # TODO: Consider adding a dummy model to $default, to force API Gateway to reject these
  #       requests and avoid paying for Lambda calls just to respond "malformed message".
  NATPunchDefaultRoute:
    Type: AWS::ApiGatewayV2::Route
    Properties:
      ApiId: !Ref NATPunchWebSocket
      RouteKey: $default
      AuthorizationType: NONE
      OperationName: NATPunchDefaultRoute
      # A Lambda proxy response is used for $default messages to immediately inform
      # the caller that the request was malformed.
      # See the matching response section following the integration definition.
      RouteResponseSelectionExpression: $default
      Target: !Join ['/', [integrations, !Ref NATPunchDefaultInteg]]

  # Lambda proxy integratino for $default route
  NATPunchDefaultInteg:
    Type: AWS::ApiGatewayV2::Integration
    Properties:
      ApiId: !Ref NATPunchWebSocket
      Description: Integration for builtin $default route
      IntegrationType: AWS_PROXY
      # All routes lead to the same Lambda function; it uses the route
      # provided by API Gateway to determine the right behavior.
      IntegrationUri:
        !Sub arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${NATPunchFunction.Arn}/invocations

  # The Lambda proxy response to $default, which returns an error message to the caller that
  # the message it sent was malformed.
  NATPunchDefaultRouteResponse:
    Type: 'AWS::ApiGatewayV2::RouteResponse'
    Properties:
      RouteId: !Ref NATPunchDefaultRoute
      ApiId: !Ref NATPunchWebSocket
      RouteResponseKey: $default

  # Custom 'pair'ing route. This involves both a route
  # definition and its integration definition, which follows.
  # Notes:
  #   * This path is async, so there is no response for it. The NATPunch Lambda function will
  #   make (asynchronous) HTTPS calls to the response URL for the websocket for each client
  #   if & when pairing information is complete.
  #   * This path uses model validation. This avoids the need to verify the syntax of the call
  #   in the Lambda function by having API Gateway check it.
  NATPunchPairRoute:
    Type: AWS::ApiGatewayV2::Route
    Properties:
      ApiId: !Ref NATPunchWebSocket
      RouteKey: pair
      AuthorizationType: NONE
      OperationName: NATPunchPairRoute
      # The next three lines can look a little confusing.
      # What they're saying is, "When you see 'pair' as the route, which
      # is value of the 'action' key at the top level of the request's body,
      # then apply 'NATPunchPairModel' to validate it."
      ModelSelectionExpression: "$request.body.action"
      RequestModels:
        pair: NATPunchWebSocketPairModel # This is a name, not a REF
      Target: !Join ['/', [integrations, !Ref NATPunchPairInteg]]

  NATPunchPairInteg:
    Type: AWS::ApiGatewayV2::Integration
    Properties:
      ApiId: !Ref NATPunchWebSocket
      Description: Pairing request integration
      IntegrationType: AWS_PROXY
      IntegrationUri:
        !Sub arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${NATPunchFunction.Arn}/invocations

  # The validation model for 'pair' route messages.
  NATPunchPairModel:
    Type: AWS::ApiGatewayV2::Model
    Properties:
      Name: NATPunchWebSocketPairModel # Must match NATPunchPairRoute.RequestModel value
      ApiId: !Ref NATPunchWebSocket
      ContentType: application/json
      Schema:
        $schema: 'http://json-schema.org/draft-04/schema#'
        title: NATPunchPairModelSchema
        type: object
        properties:
          action:       {type: string, pattern: "pair"}
          pairing_name: {type: string, pattern: "[_a-z0-9]{1,255}"}
          limit:
            type: number
        required: [action, pairing_name]

  # The custom 'status' path. This involves both a route
  # definition and its integration definition, which follows, as well as a 
  # synchronous response from the Lambda proxy.
  NATPunchStatusRoute:
    Type: AWS::ApiGatewayV2::Route
    Properties:
      ApiId: !Ref NATPunchWebSocket
      RouteKey: status
      AuthorizationType: NONE
      OperationName: NATPunchStatusRoute
      # The next three lines can look a little confusing.
      # What they're saying is, "When you see 'status' as the route, which
      # is value of the 'action' key at the top level of the request's body,
      # then apply 'NATPunchStatusModel' to validate it."
      ModelSelectionExpression: "$request.body.action"
      RequestModels:
        status: NATPunchWebSocketStatusModel # This is a name, not a REF
      # A Lambda proxy response is used for status requests to return
      # connection information to the caller.
      # See the matching response section following the integration definition.
      RouteResponseSelectionExpression: $default
      Target: !Join ['/', [integrations, !Ref NATPunchStatusInteg]]

  NATPunchStatusInteg:
    Type: AWS::ApiGatewayV2::Integration
    Properties:
      ApiId: !Ref NATPunchWebSocket
      Description: Integration for custom 'status' route
      IntegrationType: AWS_PROXY
      # All routes lead to the same Lambda function; it uses the route
      # provided by API Gateway to determine the right behavior.
      IntegrationUri: 
        !Sub arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${NATPunchFunction.Arn}/invocations

  # The Lambda proxy response to 'status', which returns connection info to the caller.
  StatusRouteResponse:
    Type: 'AWS::ApiGatewayV2::RouteResponse'
    Properties:
      RouteId: !Ref NATPunchStatusRoute
      ApiId: !Ref NATPunchWebSocket
      RouteResponseKey: $default

  # The validation model for 'status' route messages.
  NATPunchStatusModel:
   Type: AWS::ApiGatewayV2::Model
   Properties:
     Name: NATPunchWebSocketStatusModel
     ApiId: !Ref NATPunchWebSocket
     ContentType: application/json
     Schema:
       $schema: 'http://json-schema.org/draft-04/schema#'
       title: NATPunchStatusModelSchema
       type: object
       properties:
         action: {type: string, pattern: "status"}
       required: [action]