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Server-side website

The server-side-website construct deploys websites where the HTML is rendered "server-side", i.e. on AWS Lambda.

This is usually done with backend frameworks like Laravel/Symfony (PHP), Ruby on Rails, Django/Flask (Python), Express (Node), etc.

To build a SPA or static website, use the Static Website construct instead.

Quick start

service: my-app
provider:
    name: aws

functions:
    home:
        handler: home.handler
        events:
            -   httpApi: 'GET /'
    # ...

constructs:
    website:
        type: server-side-website
        assets:
            '/css/*': public/css
            '/js/*': public/js

plugins:
    - serverless-lift

On serverless deploy, the example above will set up a website that serves both:

  • https://<domain>/* -> the website through API Gateway + Lambda
  • https://<domain>/css/* and https://<domain>/js/* -> assets through S3

Note: the first deployment takes 5 minutes.

The website is served over HTTPS and cached all over the world via the CloudFront CDN.

How it works

On the first serverless deploy, Lift creates:

CloudFront serves the website over HTTPS with caching at the edge. It also provides an "HTTP to HTTPS" redirection which is not supported by API Gateway. For websites, this is problematic because it means someone typing website.com in a browser will get a blank page: API Gateway will not even redirect this to HTTPS.

Finally, CloudFront also acts as a router:

  • URLs that points to static assets are served by S3
  • all the other URLs are served by API Gateway

The construct uses the API Gateway configured in functions defined in serverless.yml.

Additionally, every time serverless deploy runs, Lift:

  • uploads the static assets to the S3 bucket
  • invalidates the CloudFront CDN cache

Note: the S3 bucket is public and entirely managed by Lift. Do not store or upload files to the bucket, they will be removed by Lift on the next deployment. Instead, create a separate bucket to store any extra file.

CloudFront configuration

CloudFront is configured to cache static assets by default, but not cache dynamic content by default. It will forward cookies, query strings and most headers to the backend running on Lambda.

Website routes

To define website routes, create Lambda functions in functions: with httpApi events:

# serverless.yml
# ...

functions:
    home:
        handler: home.handler
        events:
            -   httpApi: 'GET /'
    search:
        handler: search.handler
        events:
            -   httpApi: 'GET /search'
    # ...

constructs:
    website:
        type: server-side-website
        # ...

Check out the official documentation on how to set up HTTP events.

When using backend frameworks that provide a routing feature, another option is to define a single Lambda function that captures all the HTTP routes:

# serverless.yml
# ...

functions:
    backend:
        handler: index.handler
        events:
            -   httpApi: '*'

constructs:
    website:
        type: server-side-website
        # ...

Variables

The server-side-website construct exposes the following variables:

  • url: the URL of the deployed website (either the CloudFront URL or the first custom domain, if configured)

For example:

constructs:
    website:
        type: server-side-website
        # ...

functions:
    backend:
        # ...
        environment:
            WEBSITE_URL: ${construct:website.url}

How it works: the ${construct:website.url} variable will automatically be replaced with a CloudFormation reference.

  • cname: the CloudFront domain to point custom domains to, for example d1111abcdef8.cloudfront.net

This can be used to configure a custom domain with Route53, for example:

constructs:
    website:
        type: server-side-website
        # ...
resources:
    Resources:
        Route53Record:
            Type: AWS::Route53::RecordSet
            Properties:
                HostedZoneId: ZXXXXXXXXXXXXXXXXXXJ # Your HostedZoneId
                Name: app.mydomain
                Type: A
                AliasTarget:
                    HostedZoneId: Z2FDTNDATAQYW2 # Cloudfront Route53 HostedZoneId. This does not change.
                    DNSName: ${construct:website.cname}
  • assetsBucketName: the S3 assets bucketname

This can be used to configure a S3 bucket policy for example:

constructs:
    website:
        type: server-side-website
        # ...
resources:
    Resources:
        BucketPolicy:
            Type: AWS::S3::BucketPolicy
            Properties:
                Bucket: ${construct:website.assetsBucketName}
                # ...

Commands

serverless deploy deploys everything configured in serverless.yml and uploads assets.

When iterating, it is possible to skip the CloudFormation deployment and directly publish changes via:

  • serverless deploy function -f <function-name> to deploy a single Lambda function
  • serverless <construct-name>:assets:upload to upload assets to S3 (the CloudFront cache will be cleared as well)

Configuration reference

Assets

constructs:
    website:
        # ...
        assets:
            '/assets/*': dist/

The assets section lets users define routing for static assets (like JavaScript, CSS, images, etc.).

  • The key defines the URL pattern.
  • The value defines the local path to upload.

Assets can be either whole directories, or single files:

constructs:
    website:
        # ...
        assets:
            # Directories: routes must end with `/*`
            '/css/*': dist/css
            '/images/*': assets/animations
            # Files:
            '/favicon.ico': public/favicon.ico

With the example above:

  • https://<domain>/* -> Lambda
  • https://<domain>/css/* -> serves the files uploaded from the local dist/css directory
  • https://<domain>/images/* -> serves the files uploaded from the local assets/animations directory
  • https://<domain>/favicon.ico -> serves the file uploaded from public/favicon.ico

API Gateway

API Gateway provides 2 versions of APIs:

  • v1: REST API
  • v2: HTTP API, the fastest and cheapest

By default, the server-side-website construct supports v2 HTTP APIs.

If your Lambda functions uses http events (v1 REST API) instead of httpApi events (v2 HTTP API), use the apiGateway: "rest" option:

constructs:
    website:
        type: server-side-website
        apiGateway: 'rest' # either "rest" (v1) or "http" (v2, the default)

functions:
    v1:
        handler: foo.handler
        events:
            -   http: 'GET /' # REST API (v1)
    v2:
        handler: bar.handler
        events:
            -   httpApi: 'GET /' # HTTP API (v2)

Custom domain

constructs:
    website:
        # ...
        domain: mywebsite.com
        # ARN of an ACM certificate for the domain, registered in us-east-1
        certificate: arn:aws:acm:us-east-1:123456615250:certificate/0a28e63d-d3a9-4578-9f8b-14347bfe8123

The configuration above will activate the custom domain mywebsite.com on CloudFront, using the provided HTTPS certificate.

After running serverless deploy (or serverless info), you should see the following output in the terminal:

website:
  url: https://mywebsite.com
  cname: s13hocjp.cloudfront.net

Create a CNAME DNS entry that points your domain to the xxx.cloudfront.net domain. After a few minutes/hours, the domain should be available.

HTTPS certificate

To create the HTTPS certificate:

  • Open the ACM Console in the us-east-1 region (CDN certificates must be in us-east-1, regardless of where your application is hosted)
  • Click "Request a new certificate", add your domain name and click "Next"
  • Choose a domain validation method:
    • Domain validation will require you to add CNAME entries to your DNS configuration
    • Email validation will require you to click a link in an email sent to [email protected]

After the certificate is created and validated, you should see the ARN of the certificate.

Multiple domains

It is possible to set up multiple domains:

constructs:
    website:
        # ...
        domain:
            - mywebsite.com
            - app.mywebsite.com

Usually, we can retrieve which domain a user is visiting via the Host HTTP header. This doesn't work with API Gateway (Host contains the API Gateway domain).

The server-side-website construct offers a workaround: the X-Forwarded-Host header is automatically populated via CloudFront Functions. Code running on Lambda will be able to access the original Host header via this X-Forwarded-Host header.

Redirect all domains to a single one

It is sometimes necessary to redirect every request to a single domain. A common example is to redirect the root domain to the www version.

constructs:
    website:
        # ...
        domain:
            - www.mywebsite.com
            - mywebsite.com
        redirectToMainDomain: true

The first domain in the list will be considered the main domain. In this case, mywebsite.com will redirect to www.mywebsite.com.

Error pages

constructs:
    website:
        # ...
        errorPage: error500.html

In case a web page throws an error, API Gateway's default Internal Error blank page shows up. This can be overridden by providing an HTML error page.

Applications are of course free to catch errors and display custom error pages. However, sometimes even error pages and frameworks fail completely: this is where the API Gateway error page shows up.

Forwarded headers

Note:

In previous Lift versions, the headers forwarded to your Lambda backend were limited. You were able to add new headers via the forwardedHeaders option.

This is no longer the case: all headers are now always forwarded.

All headers are forwarded to your Lambda backend. If you used the forwardedHeaders option in the past, you can safely remove it.

Extensions

You can specify an extensions property on the server-side-website construct to extend the underlying CloudFormation resources. In the exemple below, the CloudFront Distribution CloudFormation resource generated by the website server-side-website construct will be extended with the new Comment: Landing distribution CloudFormation property.

constructs:
    website:
        type: server-side-website
        assets:
            '/css/*': public/css
            '/js/*': public/js
        extensions:
            distribution:
                Properties:
                    DistributionConfig:
                        Comment: Landing distribution

Available extensions

Extension key CloudFormation resource CloudFormation documentation
distribution AWS::CloudFront::Distribution Link
bucket AWS::S3::Bucket Link

More options

Feel like a common extension pattern should be implemented as part of the construct configuration? Open a GitHub issue.