Serverless Lerna + Yarn Workspaces Starter

A Serverless monorepo starter that uses Lerna and Yarn Workspaces.

• Designed to scale for larger projects
• Maintains internal dependencies as packages
• Uses Lerna to figure out which services have been updated
• Supports publishing dependencies as private NPM packages
• Uses serverless-bundle to generate optimized Lambda packages
• Uses Yarn Workspaces to hoist packages to the root node_modules/ directory

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Installation

To create a new Serverless project

$ git clone https://github.com/AnomalyInnovations/serverless-lerna-yarn-starter my-project

Enter the new directory

$ cd my-project

Install NPM packages for the entire project

$ yarn

How It Works

The directory structure roughly looks like:

package.json
/libs
/packages
  /sample-package
    index.js
    package.json
/services
  /service1
    handler.js
    package.json
    serverless.yml
  /service2
    handler.js
    package.json
    serverless.yml

This repo is split into 3 directories. Each with a different purpose:

• packages

  These are internal packages that are used in our services. Each contains a package.json and can be optionally published to NPM. Any changes to a package should only deploy the service that depends on it.

• services

  These are Serverless services that are deployed. Has a package.json and serverless.yml. There are two sample services.

  1. service1: Depends on the sample-package. This means that if it changes, we want to deploy service1.
  2. service2: Does not depend on any internal packages.

  More on deployments below.

• libs

  Any common code that you might not want to maintain as a package. Does NOT have a package.json. Any changes here should redeploy all our services.

The packages/ and services/ directories are Yarn Workspaces.

Services

The Serverless services are meant to be managed on their own. Each service is based on our Serverless Node.js Starter. It uses the serverless-bundle plugin (based on Webpack) to create optimized Lambda packages.

This is good for keeping your Lambda packages small. But it also ensures that you can have Yarn hoist all your NPM packages to the project root. Without Webpack, you'll need to disable hoisting since Serverless Framework does not package the dependencies of a service correctly on its own.

Install an NPM package inside a service.

$ yarn add some-npm-package

Run a function locally.

$ serverless invoke local -f get

Run tests in a service.

$ yarn test

Deploy the service.

$ serverless deploy

Deploy a single function.

$ serverless deploy function -f get

To add a new service.

$ cd services/
$ serverless install --url https://github.com/AnomalyInnovations/serverless-nodejs-starter --name new-service
$ cd new-service
$ yarn

Packages

Since each package has its own package.json, you can manage it just like you would any other NPM package.

To add a new package:

$ mkdir packages/new-package
$ yarn init

Packages can also be optionally published to NPM.

To use a package:

$ yarn add new-package@1.0.0

Note that packages should be added by specifying the version number declared in their package.json. Otherwise, yarn tries to find the dependency in the registry.

Libs

If you need to add any other common code in your repo that won't be maintained as a package, add it to the libs/ directory. It does not contain a package.json. This means that you'll need to install any NPM packages as dependencies in the root.

To install an NPM package at the root.

$ yarn add -W some-npm-package

Deployment

We want to ensure that only the services that have been updated get deployed. This means that, if a change is made to:

• services

  Only the service that has been changed should be deployed. For ex, if you change any code in service1, then service2 should not be deployed.

• packages

  If a package is changed, then only the service that depends on this package should be deployed. For ex, if sample-package is changed, then service1 should be deployed.

• libs

  If any of the libs are changed, then all services will get deployed.

Deployment Algorithm

To implement the above, use the following algorithm in your CI:

1. Run lerna ls --since ${prevCommitSHA} -all to list all packages that have changed since the last successful deployment. If this list includes one of the services, then deploy it.
2. Run git diff --name-only ${prevCommitSHA} ${currentCommitSHA} to get a list of all the updated files. If they don't belong to any of your Lerna packages (lerna ls -all), deploy all the services.
3. Otherwise skip the deployment.

Deploying Through Seed

Seed supports deploying Serverless monorepo projects that use Lerna and Yarn Workspaces. To enable it, add the following to the seed.yml in your repo root:

check_code_change: lerna

To test this:

Add the App

1. Fork this repo and add it to your Seed account.
2. Add both of the services.
3. Deploy your app once.

Update a Service

• Make a change in services/service2/handler.js and git push.
• Notice that service2 has been deployed while service1 was skipped.

Update a Package

• Make a change in packages/sample-package/index.js and git push.
• Notice that service1 should be deployed while service2 will have been skipped.

Update a Lib

• Finally, make a change in libs/index.js and git push.
• Both service1 and service2 should've been deployed.

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This repo is maintained by Serverless Stack.