aws-lambda-typescript

aws-lambda-typescript

build pipeline for easily building aws lambda functions with typescript.

creating your function

• create a new node project and npm init it.
• npm install --save-dev gulp aws-lambda-typescript
• create a gulpfile.js file
• add the following to your gulpfile.js:

const gulp = require('gulp');
const awsLambdaTypescript = require('aws-lambda-typescript');

awsLambdaTypescript.registerBuildGulpTasks(gulp, __dirname);

• run gulp lambda:init to set everything up

The following files will be created in the root of your project:

• index.ts - the entry point of your typescript lambda function
• .eslintrc.js - configures the linter
• tsconfig.json - configures the typescript compiler
• debug.js - debugging entrypoint allows simple debugging of your function in a local express instance
• lambda-config.js - contains the deployment details for your function

The following commands are then available:

• gulp lambda:init - sets up the above files
• gulp lambda:run - runs your function in a local express instance, defaults to port 9000
• gulp lambda:package - packages your function up ready for deployment by bundling everything together with webpack
• gulp lambda:deploy - packages and deploys your function
• gulp lambda:info - get info about the current state of your lambda function

running locally

after running gulp lambda:run you can test your function locally by posting to localhost:9000/

debugging

By setting your debuggers entry point to the debug.js file in the root of your project you can easily step through your function.

debugging in vscode

Go to the debug tab in visual studio at the top where it says "debug" and probably "no configurations" there should be a gear icon. Click it and you should be taken to your launch.json file that will look something like:

{
  "version": "0.2.0",
  "configurations": [
    {
      "type": "node",
      "request": "launch",
      "name": "Launch Program",
      "program": "${workspaceRoot}\\index.js",
      "outFiles": [
          "${workspaceRoot}/out/**/*.js"
      ]
    }
  ]
}

Then you should be able to debug as normal.

options

By altering lambda-config.js in the root of your project you can set the following options:

module.exports = {
  localPort: 9000, // set the port to run the local server on
  region: 'us-west-2' // set the aws region
};

There are lots of other options available but it's probably best to look at the lambda-config.js file in https://github.com/ThoughtWorksStudios/node-aws-lambda as we use that.

how it works

When running locally we spin up an express instance then use "ts-node" to allow the transparent usage of typescript and allow debugging to work. This is great but has some overhead, to keep spin-up times to a miminum we do something different when we package everything up for release. When we package the function up we run it through webpack and do a one-time transform to javascript, in this way we pay no runtime penalty for typescript compilation.

todo

• A simple way to run tests
• check interaction with other aws resources when running locally

Changelog

5.1.1

• Fix issue where packaging did not abort if compilation failed