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examples/lb4-express

This example shows how to use the serverless framework to run loopback4 (with express) in AWS Lambda.

Overview

A RDS (MySQL) database is created, along with all necessary virtual AWS infrastructure (VPC, subnets, DBSubnetGroup) to connect a lambda function running loopback4 to the MySQL database. The MySQL connection parameters are retrieved from lambda environment variables.

About Sample Provided

The sample loopback4 application provided was created by following the process below:

  1. Create an Express Application with LoopBack REST API by following this tutorial. We followed the shortcut by running the command lb4 example express-composition.

  2. Remove the file parameter from the memory datasource to avoid lambda errors.

  3. Create the following files required to deploying it all to AWS Lambda using the serverless framework:

  4. Update your tsconfig.json file to include "allowJs": true in your compilerOptions section to ensire the src/lambda-wrapper.js file is included in the loopback4 build.

  5. Install the serverless-http module and its dependencies with command npm install serverless-http.

  6. Install the serverless module and its dependencies with command npm install -D serverless.

  7. As we planed to troubleshoot locally, we installed the serverless-offline module and its dependencies with command npm install -D serverless-offline.

  8. In order to ensure your loopback4 application is built prior to deploying it to AWS Lambda or running it locally we included the following scripts in the package.json file:

    "presls-deploy": "npm run build",
    "sls-deploy": "serverless deploy --verbose",
    "sls-cleanup": "serverless remove --verbose",
    "presls-offline": "npm run build",
    "sls-offline": "serverless offline",

Please note that serverless-http also supports other web frameworks. The loopback support indicated is for @loopback-rest. Please feel free to contribute your examples of using loopback4 with other web frameworks under the examples folder.

Customizing & Deploying This Sample

The following steps can be used to customize this sample to your needs and then deploy:

  1. Create your own loopback models, datasources, repositories, and controllers.

  2. Deploy your project to AWS using the command npm run sls-deploy

  3. From the serverless Stack Outputs, retrieve LoopbackApiExplorer to access the loopback4 API explorer (it should look something like https://API_GATEWAY_ID.execute-api.AWS_REGION.amazonaws.com/SERVERLESS_STAGE/api/explorer/). You should end up with an URL similar to https://XXXXXXXXXX.execute-api.us-east-1.amazonaws.com/dev/api/explorer/.

  4. From the lopback4 API explorer download the openapi.json file and import it into Postman. After importing, make sure to edit the imported collection and change the baseUrl variable to the value of the serverless LoopbackPostman Stack Outputs. This will make sure Postman works with your serverless API Gateway rather than the loopback4 only path.

Cleaning Up The Sample

Once you are done with the sample environment, avoid unnecessary AWS charges by removing your serverless deployment with the command npm run sls-cleanup.

Known Issues

While the serverless deployment works fine, invoking the API through API explorer never reaches API Gateway as CloudFront responds with Code 403:

Response body

{
  "message": "Forbidden"
}

Response headers

 content-length: 24
 content-type: application/json
 date: Sun14 Jun 2020 14:14:09 GMT  via: 1.1 0dfe6f02dbba7c39906cae47653ae6b3.cloudfront.net (CloudFront)
 x-amz-apigw-id: OOYDwFjZiYcFSAA=
 x-amz-cf-id: 3SvwvE27qb1KIrS34rgRRwet-QOkfZyFeJOIMUbHMgi6dA5-BgBEeg==
 x-amz-cf-pop: DEN50-C2
 x-amzn-errortype: ForbiddenException
 x-amzn-requestid: 31a0c024-6ffe-4c3c-b9d9-adfca9add4b0
 x-cache: Error from cloudfront
 x-firefox-spdy: h2

License

MIT © BotBitsSM