Lambda Express

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

Features

  • Express.js server running on AWS Lambda
  • Very low cost, scalability out of the box
  • Server packaged up using eslint for small deployment size and quick on-demand start in Lambda
  • All infrastructure defined in Terraform, easy to change and extend
  • Infrastructure easily rolled out with dedicated npm script
  • Deployment automated using Node.js module
  • TypeScript, ESLint and Prettier configured

Configure

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

  • Lambda Name: The name to be used for this lambda. Lambda names need to be unique for the AWS Region. It is not possible to have two lambdas with the same name in the same region.
  • API Domain: The domain where the API should be deployed to. For instance, to be able to call the API endpoint https://api.mydomain.com/ the API domain api.mydomain.com needs to be configured.
  • Hosted Zone Domain: A Route 53 hosted zone that will allow adding the API Domain as a record. For instance, in order to configure the API domain api.mydomain.com, the hosted zones api.mydomain.com or mydomain.com would be valid. For more details, please check Hosted Zone Configuration in the Goldstack documentation.
  • CORS Header: An optional CORS header to enable a UI that is hosted on a different domain to access this API. For instance, for a UI that is deployed to the domain ui.mydomain.com the CORS header https://ui.mydomain.com should be supplied. To learn more about CORS, see the Cross-Origin Resource Sharing (CORS) in the MDN docs.

Getting Started

1. Project Setup

Before using this template, you need to configure the project. For this, please see the Getting Started Guide on the Goldstack documentation.

2. Setup Infrastructure

To stand up the infrastructure for this module, 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.

3. Deploy Application

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 template in the directory [moduleDir]/infra/aws. You can define multiple deployments for this template, 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 template can be run using yarn. There are four commands in total:

  • yarn infra up: For standing up infrastructure.
  • yarn infra init: For initialising Terraform.
  • yarn infra plan: For running Terraform plan.
  • yarn infra apply: For running Terraform apply.
  • yarn infra destroy: For destroying all infrastructure using Terraform destroy.
  • yarn infra upgrade: For upgrading the Terraform versions (supported by the template). To upgrade to an arbitrary version, use yarn infra terraform.
  • yarn infra terraform: For running arbitrary Terraform commands.

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.

Note that for running yarn infra terraform, you will need to specify which command line arguments you want to provide to Terraform. By default, no extra arguments are provided:

yarn infra terraform [deployment] plan

If extra arguments are needed, such as variables, you can use the --inject-variables option, such as for running terraform plan:

yarn infra terraform [deployment] --inject-variables plan

If you want to interact with the remote backend, you can also provide the --inject-backend-config option, such as for running terraform init:

yarn infra terraform [deployment] --inject-backend-config init

Customizing Terraform

Goldstack templates 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 template 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 template 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 package, 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 template. 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

Troubleshooting and Frequently Asked Questions

DNS Name for API Cannot be resolved

After applying yarn infra up [deployment] and yarn deploy [deployment] it is not possible to call the API at https://[configuration.apiDomain]. An error such as Address cannot be resolved or DNSProbe failed is reported.

This is caused by changes to the deployed DNS hosted zone needing some time to propagate through the DNS network. Wait for 10-30 min and the API should be able to be called without problems. To validate your DNS name has been configured correctly, go to the AWS Route 53 Console, choose the region you have deployed, and validate there is a correct entry for the hosted zone you have selected. There should be an A entry such as the following:

[apiDomain].[hostedZone] A [id].cloudfront.net.

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".

© 2022 Pureleap Pty. Ltd. and Contributors