Yi Ai

@yia333

Building a Fully Serverless Realtime CMS using AWS Appsync and Aurora Serverless

AWS made a serverless option of AWS RDS Aurora generally available, It would mean a breakthrough in building fully serverless architectures with relational database. No more managing connection pools with SQL, No more worrying about RDS instances, Cost is based on the compute time services are consumed, and there is no charge when code is not running.

In this post , my goal was to build a fully-functional AWS AppSync-driven backend and React frontend of a post management app. The app will deliver end users a set of features that allow public users view posts, admin users add/delete post, Let’s start!

Application Architecture

The application architecture uses:

  • Serverless framework
  • AWS Appsync
  • AWS Cognito Userpool and Identity Pool
  • AWS Aurora Serverless
  • AWS Lambda

Prerequisites

The following must be done before following this guide:

  • Setup an AWS account
  • Install the AWS CLI
  • Configure the AWS CLI with user credentials
  • Install the Serverless framework from NPM
$ npm install -g serverless

Backend

Create a new service

Create a new service using the AWS Python template, specifying a unique name and an optional path.

$ sls create --template aws-nodejs --path simpleCMS

In the app folder, there is a serverless.yml file. This file is needed to configure how our application will behave.

Configuring Appsync

Install serverless-appsync-plugin

npm install serverless-appsync-plugin

Add serverless-appsync-plugin to the plugins section of serverless.yml

plugins:
   - serverless-appsync-plugin

Add the following config to the custom section of serverless.yml

custom:
  appSync:
    region: ${self:provider.region}
    name: ${self:service.name}-${self:provider.stage}
    authenticationType: AWS_IAM
    serviceRole: "${self:service.name}-AppSyncServiceRole"
    userPoolConfig:
      awsRegion: "${self:provider.region}"
      userPoolId: ${self:custom.userPool.${self:provider.stage}}
      defaultAction: ALLOW
    mappingTemplates:
      - type: Query
        dataSource: LambdaSource
        field: getPosts
        request: "Query-getPosts-request.vtl"
        response: "Query-getPosts-response.vtl"
      - type: Post
        dataSource: LambdaSource
        field: author
        request: "Query-author-request.vtl"
        response: "Query-author-response.vtl"
      - type: Mutation
        field: addPost
        request: Mutation-addPost-request.vtl
        response: common-response.vtl
        kind: PIPELINE
        functions:
          - addPost
          - sendNotification
      - type: Mutation
        dataSource: LambdaSource
        field: deletePost
        request: Mutation-deletePost-request.vtl
        response: common-response.vtl
    functionConfigurations:
      - dataSource: LambdaSource
        name: "addPost"
        request: "Function-addPost-request.vtl"
        response: "common-response.vtl"
      - dataSource: LambdaSource
        name: "sendNotification"
        request: "Function-sendNotification-request.vtl"
        response: "Function-sendNotification-response.vtl"
    dataSources:
      - type: AWS_LAMBDA
        name: LambdaSource
        description: "Lambda DataSource"
        config:
          functionName: graphql
          lambdaFunctionArn: { Fn::GetAtt: [GraphqlLambdaFunction, Arn] }
          serviceRoleArn: { Fn::GetAtt: [AppSyncLambdaServiceRole, Arn] }

You can get all mapping templates from GitHub repo.

Next, create a IAM service role for Appsync:

Configuring Cognito

Add following config to resources section in serverless.yml

Note that above config would create a Cognito identity pool supports both authenticated and unauthenticated users, then a system admin user will be added to Cognito user pool and send out an email with temporary password to provided email address, eg.

InitialSystemAdminUser:
    Type: AWS::Cognito::UserPoolUser
    Properties:
      UserPoolId:
        Ref: CognitoUserPool
      Username: "test@neami.app"
      DesiredDeliveryMediums:
        - EMAIL
      ForceAliasCreation: true
      UserAttributes:
        - Name: email
          Value: "test@neami.app"
        - Name: name
          Value: Admin

Configuring RDS Aurora Serverless

To setup RDS Aurora Serverless, we also need to create a VPC and at least 2 subnets to database, config should like as below

To link Appsync lambda datasource to RDS, you will need to add Aurora RDS’ VPC config we just configured to providers section

provider:
  vpc:
    securityGroupIds:
      - Fn::GetAtt: [DatabaseVpcSecurityGroup, GroupId]
    subnetIds:
      - Ref: PrivateSubnet1
      - Ref: PrivateSubnet2

You can find full serverless.yml here.

Designing Graphql Schema

Schema files are text files, usually named schema.graphql. In this project schema would look like the following

Adding Lambda function

Now, let’s update our handler.js to configure our database connection and do some query, This is how the handler.py file looks like:

That is all about the backend, Let’s deploy the service.

Serverless framework makes deployments quick and painless. All you need to do is to run one command:

$ sls deploy --stage dev

It will automagically provision resources on AWS, package up and push all code to S3 from where it will be sent to the Lambdas. The terminal should show output similar to this

React Frontend

I assume you already have something loading just using react (create using create-react-app). To execute GraphQL queries from React with AWS AppSync, the following libraries are required:

I hope you have found this article useful, You can find complete project in my GitHub repo:

yai333/AppsyncServerlessCMS

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