Goldstack's Lambda Express module provides a basic Express.js server that is deployed as an AWS lambda function.

Features

Configure

The following key properties need to be configured for this module:

Getting Started

Infrastructure

The first thing we recommend to do with a new module is to stand up the infrastructure for the module. For this, find the directory for this module in the packages/ folder and navigate to this folder in the command line. Then identify the name of the deployment you have defined in the Goldstack configuration tool. This can be found in the packages/[moduleName]/goldstack.json file. Look for the "deployments" property and there for the "name" of the first deployment. The name should either be dev or prod.

In order to stand up the infrastructure, run the following command:

yarn infra up [deploymentName]

This will be either yarn infra up dev or yarn infra up prod depending on your choice of deployment. Note that running this command can take a while.

Note that your API will not work yet. It first needs to be deployed as per instructions below.

Deployment

Once the infrastructure is successfully set up in AWS using yarn infra up, we can deploy the module. For this, simply run the following command: 

yarn deploy [deploymentName]

This will either be yarn deploy dev or yarn deploy prod depending on your choice of deployment during project configuration.

You should now be able to access your API. The domain under which the API is deployed is configured in goldstack.json under "deployments[*].apiDomain". You can access this API domain with a browser since the default API provided in the template allows for GET requests to the root.

Development

The source code for the express server is defined in the src/ folder. The entry point for defining new routes is in src/server.ts. The easiest way to get started extending the API is to modify or add new routes to the server here.

Infrastructure

All infrastructure for this module is defined in Terraform. You can find the Terraform files for this module in the directory [moduleDir]/infra/aws. You can define multiple deployments for this module, for instance for development, staging and production environments.

If you configured AWS deployment before downloading your project, the deployments and their respective configurations are defined in [moduleDir]/goldstack.json.

The configuration tool will define one deployment. This will be either dev or prod depending on your choice during project configuration. In the example goldstack.json below, a deployment with the name dev is defined. 

{
  "$schema": "./schemas/package.schema.json",
  "name": "...",
  "template": "...",
  "templateVersion": "...",
  "configuration": {},
  "deployments": [
    {
      "name": "dev",
      "awsRegion": "us-west-2",
      "awsUser": "awsUser",
      "configuration": {
        ...
      }
    }
  ]
}

Infrastructure Commands

Infrastructure commands for this module can be run using yarn. There are four commands in total:

For each command, the deployment they should be applied to must be specified. 

yarn infra [command] [deploymentName]

For instance, to stand up the infrastructure for the dev deployment, the following command would need to be issued: 

yarn infra up dev

Generally you will only need to run yarn infra up. However, if you are familiar with Terraform and want more fine-grained control over the deployment of your infrastructure, you can also use the other commands as required.

Customizing Terraform

Goldstack modules make it very easy to customize infrastructure to your specific needs. The easiest way to do this is to simply edit the *.tf files in the infra/aws folder. You can make the changes you need and then run yarn infra up [deploymentName] to apply the changes.

The infra/aws folder contains a file variables.tf that contains the variables required for your deployment; for instance the domain name for a website. The values for these variables are defined in the module's goldstack.json file in the "configuration" property. There is one global configuration property that applies for all deployments and each deployment also has its own configuration property. In order to add a new variable, add the variable to variables.tf and then add it to the configuration for your module or to the configurations for the deployments.

Note that due to JavaScript and Terraform using different conventions for naming variables, Goldstack applies a basic transformation to variable names. Camel-case variables names are converted to valid variables names for Terraform by replacing every instance of a capital letter C with _c in the variable name. For instance:

myVariableName in the Goldstack configuration will translate to the Terraform variable my_variable_name as defined in variables.tf.

Terraform State

In order to manage your infrastructure, Terraform maintains a state for each deployment; to calculate required changes when the infrastructure is updated and also for destroying the infrastructure if it is no longer required. Goldstack by default will store the terraform state in the infra/aws folder as simple files.

This works well for deploying infrastructure from your local development environment but is not a good choice when building a CI/CD pipeline for the infrastructure definition. In that case, it is better to define Remote State. A popular choice many projects adopt here is to store the state in an S3 bucket. Please see the Terraform documentation for further details.

Deployment

This module can be packaged up and deployed to the deployments specified in goldstack.json. Note that deployment will only work after the infrastructure for the respective deployment has been stood up. To deploy your module, run the following script: 

yarn deploy [deploymentName]

Guides and How To

Adding environment variables

Environment variables are defined in the Terraform source code for this module. Specifically they are defined in the infra/aws/lambda.tf file in the resource resource "aws_lambda_function" "main". By default, there is one environment variable specified that identifies the Goldstack deployment used. 

 environment {
    variables = {
      GOLDSTACK_DEPLOYMENT = var.name
    }
  }

Add your environment variables into the variables map: 

 environment {
    variables = {
      GOLDSTACK_DEPLOYMENT = var.name
      YOUR_ENV_VAR = 'your env var value'
    }
  }

Usually environment variables should have different values depending on which environment the server is deployed to. This can be accomplished using Terraform variables. Change your variable declaration to the following: 

YOUR_ENV_VAR = var.my_env

Then go into the file infra/aws/variables.tf and add the following definition: 

variable "my_env" {
  description = "My environment variable"
  type = string
}

And finally add this variable to all deployment configurations in goldstack.json: 

      "configuration": {
        "lambdaName": "my-lambda",
        "apiDomain": "api.mysite.com",
        "hostedZoneDomain": "mysite.com",
        "cors": "https://mysite.com",
        "myEnv": "Value for deployment"
      }

Note that the Terraform variable my_env translates to myEnv in the JSON definition (Just remove all _ and make the first character after _ uppercase for your variable definitions).

Lastly, to support local development make sure to define the variable correctly in all scripts in package.json. Specifically, you may want to define them for "test", "test:ci" and "watch". 

    "test": "MY_ENV=localvalue jest --passWithNoTests --watch --config=jest.config.js",
    "test:ci": "MY_ENV=localvalue jest --passWithNoTests --config=jest.config.js --detectOpenHandles",
    "watch": "PORT=8731 MY_ENV=localvalue nodemon --config nodemon.json --exec 'yarn node dist/src/local.js'"

Note that for credentials and other values that should not be committed to source code, it may be better to store these in AWS Secrets Manager and retrieve them using the AWS SDK based on the process.env.GOLDSTACK_DEPLOYMENT value provided.

It is also possible to provide the value of Terraform variables through environment variables during build time. For instance, if you have defined the variable my_env, simply provide the environment variable MY_ENV when calling yarn infra. 

MY_ENV=value yarn infra up prod

This works very well in combination with secrets for GitHub actions.

- name: Deploy API
  run: |
    yarn workspace my-api infra up prod
  env:
    MY_ENV: ${{secrets.MY_ENV}}
    AWS_USER_NAME: goldstack-prod
    AWS_ACCESS_KEY_ID: ${{secrets.PROD_AWS_ACCESS_KEY_ID}}
    AWS_SECRET_ACCESS_KEY: ${{secrets.PROD_AWS_SECRET_ACCESS_KEY}}
    AWS_DEFAULT_REGION: us-west-2

Security Hardening

This module requires further security hardening when deployed in critical production applications. Specifically the lambda is given the role arn:aws:iam::aws:policy/AdministratorAccess" and this will grant the lambda access to all resources on the AWS account, including the ability to create and destroy infrastructure. It is therefore recommended to grant this lambda only rights to resources it needs access to, such as read and write permissions for an S3 bucket. This can be modified in infra/aws/lambda.tf in the resource resource "aws_iam_role_policy_attachment" "lambda_admin_role_attach".