A simple RESTful API which provides a service for storing, updating, retrieving and deleting Person entities in Dynamodb using AWS Lambda, API Gateway and ServerlessFramework.

Prerequisite

1. Install serverless globally (The Serverless Framework is a free and open-source web framework written using Node.js. Serverless is the first framework that was originally developed for building applications exclusively on AWS Lambda, a serverless computing platform provided by Amazon as a part of the Amazon Web Services.) More information related Serverless Framework can be found on serverless.com

   npm install serverless -g

2. Configure AWS credentials - through which we are going to deploy the architecture in AWS.

   Note - A aws user you are using for deployment should have proper roles assign to it to deploy AWS services such as Lambda, API Gateway, Dynamodb, IAM and S3 using CLoudFormation stack. A CloudFormation role to create/setup the AWS resources/services using cloudformation stack.

   sls config credentials --provider aws --key {Access key ID} --secret {Secret access key}

3. The rolearn you are using in serverless.yml should have right permission/role assigned to (post/create, get, update, delete) entry in Dynamodb table. This role is going to be get assigned to Lambda function we are going to deploy using CloudFormation.

   Note - While using current serverless.yml file make sure you will put the valid rolearn into it. Currently it is having an dummy and commented role and rolearn statement present in it. If you do not edit it and use this serverless file as it the serverless will create a default role for your lambda; but that role will not have a policy attached to it for adding/posting data in dynamodb. You have to manually assign policy to that role to perform post, get and to delete data in dynamodb.

Deploy

1. Deploy your code using serverless framework using below command also make sure you will run command where you have your serverless.yml file.

   sls deploy

Somethings about Serverless

1. Stack Name

   service: TTdevelopement
   

2. Lambda Function Example

    postuser:                                          #name of Lambda function
      handler: src/function/postuser/handler.handler   #source code file
      events:                                          #API Gateway event
        - http:                                        
            path: person                               #Resource path and method
            method: post
   
   
   

3. Dynamodb table creation using resource AWS infrastructure resources which the AWS Lambda functions in your Service depend on, like AWS DynamoDB or AWS S3. Using the Serverless Framework, you can define the infrastructure resources you need in serverless.yml, and easily deploy them.

    Resources:
      usertable:
        Type: AWS::DynamoDB::Table
        Properties:
          TableName: userinformation
          AttributeDefinitions:
            - AttributeName: id
              AttributeType: S
          KeySchema:
            - AttributeName: id
              KeyType: HASH
          ProvisionedThroughput:
            ReadCapacityUnits: 1
            WriteCapacityUnits: 1
          StreamSpecification:
            StreamViewType: NEW_AND_OLD_IMAGES
             
   

Input

1. POST USER While posting user information make sure you use unique id while posting new user entry to dynamodb. first_name, last_name, age and favourite_colour are mandatory fields while posting user information.

   curl -X POST https://{apigatewayendpoint}/dev/person -d '{
   "id":"1",
   "first_name": "John",
   "last_name": "Keynes",
   "age": "29",
   "favourite_colour": "red"
   }'
   
   

2. GET USER

   curl -X GET https://{apigatewayendpoint}/dev/person/ids/1
   
   

3. UPDATE User Information

   curl -X PUT https://{apigatewayendpoint}/dev/person/ids/1 -d '{
   "fields": {
   "last_name":"Taylor"
   }
   }'
   
   

4. DELETE USER info/entry from table

   curl -X DELETE https://{apigatewayendpoint}/dev/person/ids/1
   
   
   

ERROR HANDLING

Above code has been tested for various user-inputs and it is handling almost all user errors.
For eample
         1. Wrong field while posting user information.
         2. Missing field check while posting user information.
         3. Unique id check while posting user information.
         4. Wrong user id while retriving user information.
         5. Wrong id check while updating user information.
         6. Wrong field while updating/modifying user information.
         7. Wrong id while deleting user information for dynamodb table.
         8. Wrong user id while retriving user information.
         9. Wrong **method** or **pathParameters** while usig above code.