template.yml

AWSTemplateFormatVersion : '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: Pipeline example serverless application

Outputs:
  APIRoot:
    Description: Url of the API
    Export:
      # Every export needs an account wide unique name
      Name:
        'Fn::Sub': '${AWS::StackName}-apiroot'
    Value:
      'Fn::Sub': 'https://${RestAPI}.execute-api.${AWS::Region}.amazonaws.com/prod'

Resources:
  HelloWorldLambda:
    Type: AWS::Serverless::Function
    Properties:
      Handler: index.handler
      CodeUri: .
      Runtime: nodejs6.10
      Timeout: 3
      Role: !GetAtt HelloWorldLambdaRole.Arn
      Events:
        RootGet:
          Type: Api
          Properties:
            RestApiId: !Ref RestAPI
            Path: /
            Method: GET
      # for gradual deployment, we need an alias. We just call it live
      AutoPublishAlias: live
      DeploymentPreference:
        # Shift 10 percent of the traffic every minute
        Type: Linear10PercentEvery1Minute
        Alarms:
            # larm that aborts the deployment
            # alarm is created below!
            - !Ref HelloWorldLambdaAlarm
  RestAPI:
    Type: 'AWS::Serverless::Api'
    Properties:
      StageName: prod
      DefinitionBody:
        swagger: '2.0'
        info:
          title: !Sub '${AWS::StackName}-API'
        basePath: /prod
        schemes:
          - https
        paths:
          /:
            get:
              responses: {}
              x-amazon-apigateway-integration:
                # Append alias live to the ARN of the lambda
                uri: !Sub >-
                  arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${HelloWorldLambda.Arn}:live/invocations
                passthroughBehavior: when_no_match
                httpMethod: POST
                type: aws_proxy
  HelloWorldLambdaRole:
    Properties:
      AssumeRolePolicyDocument:
        Statement:
          - Action:
              - 'sts:AssumeRole'
            Effect: Allow
            Principal:
              Service:
                - lambda.amazonaws.com
        Version: 2012-10-17
      Path: /
      ManagedPolicyArns:
          - arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole
    Type: 'AWS::IAM::Role'
  # This alarm monitors the errors of the HelloWorld lambda function
  HelloWorldLambdaAlarm:
    Type: 'AWS::CloudWatch::Alarm'
    Properties:
      AlarmDescription: Errors of Hello World function (${AWS::StackName})
      AlarmName: !Sub 'Hello World Errors ${AWS::StackName}'
      # if more than zero (threshold below) errors occur, change state
      # to alarm
      ComparisonOperator: GreaterThanThreshold
      EvaluationPeriods: 1
      MetricName: Errors
      Namespace: AWS/Lambda
      # monitor last five minutes
      Period: 300
      Statistic: Sum
      Threshold: 0
      # if there was no invocation, the alarm state is OK
      TreatMissingData: notBreaching