CloudFormation Sample Template

cloudformation-sample.template

AWSTemplateFormatVersion: "2010-09-09"
Description: "CloudFormation sample template with Lambda function for OpenWeatherMap API"
Parameters:
  # Parameters let users input custom values into template when creating a stack
  OpenWeatherMapApiKey:
    Type: "String"
    Description: "The API key for your OpenWeatherMap account, i.e. 8b2b9..."
  TriggerRateMinutes:
    Type: "Number"
    Description: "How often the Lambda functions are invoked to keep them warm"
    Default: 30
Resources:
  # IAM role to for a Lambda to execute itself
  executeOwnLambdaIAMRole:
    Type: "AWS::IAM::Role"
    Properties:
      AssumeRolePolicyDocument:
        Version: "2012-10-17"
        Statement:
          Effect: "Allow"
          Principal:
            Service:
              - "lambda.amazonaws.com"
          Action:
            - "sts:AssumeRole"
      ManagedPolicyArns:
        - "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole"
  # Node.js Lambda function that converts a city name to an OpenWeatherMap API city id
  getOpenWeatherMapCityIdLambdaFunction:
    Type: "AWS::Lambda::Function"
    Properties:
      Description: "Gets the OpenWeatherMap API city id for a city"
      Code:
        ZipFile: !Sub |
          exports.handler = (event, context, callback) => {
            const cityName = event.cityName;
            console.log(
              "Looking up city id for " + cityName
            );
            //hardcoded for sample purposes;
            var cityId = 4887398; //Chicago
            callback(null, { cityName: cityName, cityId: cityId});
          }
      Handler: "index.handler"
      Role: !GetAtt 
        - "executeOwnLambdaIAMRole"
        - "Arn"
      Runtime: "nodejs6.10"
      Timeout: 8
      MemorySize: 128
    DependsOn:
      - "executeOwnLambdaIAMRole"
  # IAM role to for a Lambda to execute itself and also execute the getOpenWeatherMapCityId
  executeOwnAndGetCityIdLambdaIAMRole:
    Type: "AWS::IAM::Role"
    Properties:
      AssumeRolePolicyDocument:
        Version: "2012-10-17"
        Statement:
          Effect: "Allow"
          Principal:
            Service:
              - "lambda.amazonaws.com"
          Action:
            - "sts:AssumeRole"
      ManagedPolicyArns:
        - "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole"
      Policies: 
        - 
          PolicyName: "invokeCityIdLambda"
          PolicyDocument: 
            Version: "2012-10-17"
            Statement: 
              - 
                Effect: "Allow"
                Action: "lambda:InvokeFunction"
                Resource:
                  - !GetAtt 
                    - "getOpenWeatherMapCityIdLambdaFunction"
                    - "Arn"
  # Node.js Lambda function that gets current weather information from OpenWeatherMap API based on city
  getCurrentWeatherForCityLambdaFunction:
    Type: "AWS::Lambda::Function"
    Properties:
      Description: "Looks up current weather conditions in a city from OpenWeatherMap API"
      Code:
        ZipFile: !Sub |
          const https = require("https");
          const aws = require("aws-sdk");
          const openWeatherMapApiKey = process.env["OpenWeatherMapApiKey"];
          
          exports.handler = (event, context, callback) => {
            const cityName = event.Details.ContactData.Attributes.CityName;
            var lambda = new aws.Lambda({
              region: "${AWS::Region}"
            });
            var payloadObject = { cityName: event.Details.ContactData.Attributes.CityName };
            lambda.invoke(
              {
                FunctionName: "${getOpenWeatherMapCityIdLambdaFunction}",
                Payload: JSON.stringify(payloadObject)
              },
              function(error, data) {
                if (error) {
                  console.error("Failed to invoke Lambda to get city id", error);
                  callback("Failed to invoke Lambda to get city id: " + error);
                }
                if (data) {
                  var cityId = JSON.parse(data.Payload).cityId;
                  console.log("Got city id " + cityId + " for city " + cityName);
                  //make open weather api call
                  const queryString = "/data/2.5/weather?id=" + cityId + "&appid=" + openWeatherMapApiKey;
                  console.log("Querying API for weather with query string of " + queryString);
                  //hardcoded for sample purposes
                  callback(null, { name: "Chicago", weather: "Mist" });
                }
              }
            );
          }
      Handler: "index.handler"
      Role: !GetAtt 
        - "executeOwnAndGetCityIdLambdaIAMRole"
        - "Arn"
      Runtime: "nodejs6.10"
      Timeout: 8
      MemorySize: 128
      Environment:
        Variables:
          OpenWeatherMapApiKey: !Sub ${OpenWeatherMapApiKey}
    DependsOn:
      - "executeOwnAndGetCityIdLambdaIAMRole"
  # permission so that connect can invoke it
  getCurrentWeatherForCityLambdaFunctionInvokePermission:
    Type: AWS::Lambda::Permission
    DependsOn: getCurrentWeatherForCityLambdaFunction
    Properties:
      FunctionName:
        Ref: getCurrentWeatherForCityLambdaFunction
      Action: lambda:InvokeFunction
      Principal: connect.amazonaws.com
      SourceAccount:
        Ref: AWS::AccountId
  # CloudWatch Event to periodically trigger the sample Lambda functions
  sampleLambdaFunctionsTrigger:
    Type: 'AWS::Events::Rule'
    Properties:
      ScheduleExpression: !Sub rate(${TriggerRateMinutes} minutes)
      State: 'ENABLED'
      Targets:
        - 
          Arn:
            Fn::GetAtt:
              - "getOpenWeatherMapCityIdLambdaFunction"
              - "Arn"
          Input: '{ "Name": "CloudWatchEvent", "Type": "KeepWarm"}'
          Id: "getOpenWeatherMapCityIdLambdaFunctionTarget1"
        - 
          Arn:
            Fn::GetAtt:
              - "getCurrentWeatherForCityLambdaFunction"
              - "Arn"
          Input: '{ "Name": "CloudWatchEvent", "Type": "KeepWarm"}'
          Id: "getCurrentWeatherForCityLambdaFunctionTarget1"
  # Permissions for the CloudWatch Event to periodically trigger the getOpenWeatherMapCityId Lambda function
  getOpenWeatherMapCityIdLambdaFunctionTriggerInvokePermission:
    Type: "AWS::Lambda::Permission"
    Properties:
      FunctionName:
        Ref: "getOpenWeatherMapCityIdLambdaFunction"
      Action: "lambda:InvokeFunction"
      Principal: "events.amazonaws.com"
      SourceArn: 
       Fn::GetAtt:
        - "sampleLambdaFunctionsTrigger"
        - "Arn"
  # Permissions for the CloudWatch Event to periodically trigger the getCurrentWeatherForCity Lambda function
  getCurrentWeatherForCityLambdaFunctionTriggerInvokePermission:
    Type: "AWS::Lambda::Permission"
    Properties:
      FunctionName:
        Ref: "getCurrentWeatherForCityLambdaFunction"
      Action: "lambda:InvokeFunction"
      Principal: "events.amazonaws.com"
      SourceArn: 
       Fn::GetAtt:
        - "sampleLambdaFunctionsTrigger"
        - "Arn"
Outputs:
  getOpenWeatherMapCityIdLambdaARN:
    Description: "ARN of the getOpenWeatherMapCityId Lambda function"
    Value:
      Fn::GetAtt:
        - "getOpenWeatherMapCityIdLambdaFunction"
        - "Arn"
  getCurrentWeatherForCityLambdaARN:
    Description: "ARN of the getCurrentWeatherForCity Lambda function"
    Value:
      Fn::GetAtt:
        - "getCurrentWeatherForCityLambdaFunction"
        - "Arn"