Deploy to S3 via GitHub Webhook and AWS Lambda

The code here is deployed to AWS Lambda which my personal website's repo triggers via a GitHub webhook on updates.

The code fetches the latest version of the website repo from GitHub, sync's the public/ folder to S3 and optionally creates a CloudFront invalidation to clear the cache.

Setup

This project works by setting a GitHub webhook to trigger an API setup using AWS API Gateway which simply triggers an [AWS Lambda].

I created AWS API and Lambda instances manually but the serverless project has an example that may work to automatically configure API and Lambda for you. Once those are set up, you can copy the rest of the code from here and deploy that.

Additionally, the Amazon Linux image used in lambda currently doesn't have Git. So this layer should be added to the lambda function to have Git available.

Here are all the environment variables that need to be defined in the AWS Lambda configuration.

• AWS_S3_BUCKET: bucket to sync to
• GITHUB_REPO: The repo where the S3 assets are synced from
• GITHUB_TOKEN: A GitHub token for your account
• GITHUB_USER: GitHub username
• GITHUB_WEBHOOK_SECRET: https://developer.github.com/webhooks/securing/
• USER_AGENT: Can be anything, something identifying you our your repo is preferred
• AWS_CLOUDFRONT_DISTRIBUTION: Optional, distribution ID
• REGEN_PUBLIC_CMD: This should be defined only if this command should be run as part of the hook. If this command changes the repo, they will be committed back to the repo.

I bumped up the timeout to be one minute from the default of 3 seconds. On average my runs are taking about 9 seconds. I kept all other settings to their default values (including the 128 MB memory).

Deploy

export.sh from this repo can be used as an example for how to deploy to AWS lambda.

zip and aws cli tools are required. aws CLI can be installed by following https://docs.aws.amazon.com/cli/latest/userguide/cli-chap-install.html.

aws also need to be configured with a user that is permissioned with full lambda permissions on AWS. If you are managing multiple AWS credentials, you can use the named profiles features. Otherwise you can skip the --profile <name> argument from the command.

Note: You will have to npm install once locally since those dependencies need to be packaged and deployed to Lambda as well.

Caveats

• Each build looks at the commits in the webhook and only uploads files that are modified or added and deletes files that were removed in those commits.
• GitHub webhooks timeout after 10 seconds so its possible that GitHub will report a timeout but the build will still continue and succeed.