heroku-buildpack-static

NOTE: This buildpack is in an experimental OSS project.

This is a buildpack for handling static sites and single page web apps.

For a guide, read the Getting Started with Single Page Apps on Heroku.

Features

• serving static assets
• gzip on by default
• error/access logs support in heroku logs
• custom configuration

Deploying

The static.json file is required to use this buildpack. This file handles all the configuration described below.

1. Set the app to this buildpack: $ heroku buildpacks:set https://github.com/heroku/heroku-buildpack-static.git.
2. Deploy: $ git push heroku master

Configuration

You can configure different options for your static application by writing a static.json in the root folder of your application.

Root

This allows you to specify a different asset root for the directory of your application. For instance, if you're using ember-cli, it naturally builds a dist/ directory, so you might want to use that intsead.

{
  "root": "dist/"
}

By default this is set to public_html/

Default Character Set

This allows you to specify a character set for your text assets (HTML, Javascript, CSS, and so on). For most apps, this should be the default value of "UTF-8", but you can override it by setting encoding:

{
    "encoding": "US-ASCII"
}

NGINX Configuration

Client Max Body Size

By default, nginx has a default max body size of 1 megabyte. Any request above this size (e.g. uploading a 2m file) will result in a 413 Request Entity too Large error. You can configure this value by setting max_body_size:

{
  "max_body_size": "10m"
}

The size setting follows nginx's convention of bytes, kilobytes and megabytes (1024, 8k, 1m).

Clean URLs

For SEO purposes, you can drop the .html extension from URLs for say a blog site. This means users could go to /foo instead of /foo.html.

{
  "clean_urls": true
}

By default this is set to false.

Logging

You can disable the access log and change the severity level for the error log.

{
  "logging": {
    "access": false,
    "error": "warn"
  }
}

By default access is set to true and error is set to error.

The environment variable STATIC_DEBUG can be set, to override the error log level to error.

Custom Routes

You can define custom routes that combine to a single file. This allows you to preserve routing for a single page web application. The following operators are supported:

• * supports a single path segment in the URL. In the configuration below, /baz.html would match but /bar/baz.html would not.
• ** supports any length in the URL. In the configuration below, both /route/foo would work and /route/foo/bar/baz.

{
  "routes": {
    "/*.html": "index.html",
    "/route/**": "bar/baz.html"
  }
}

Browser history and asset files

When serving a single page app, it's useful to support wildcard URLs that serves the index.html file, while also continuing to serve JS and CSS files correctly. Route ordering allows you to do both:

{
  "routes": {
    "/assets/*": "/assets/",
    "/**": "index.html"
  }
}

Custom Redirects

With custom redirects, you can move pages to new routes but still preserve the old routes for SEO purposes. By default, we return a 301 status code, but you can specify the status code you want.

{
  "redirects": {
    "/old/gone/": {
      "url": "/",
      "status": 302
    }
  }
}

Interpolating Env Var Values

It's common to want to be able to test the frontend against various backends. The url key supports environment variable substitution using ${ENV_VAR_NAME}. For instance, if there was a staging and production Heroku app for your API, you could setup the config above like the following:

{
  "redirects": {
    "/old/gone/": {
      "url": "${NEW_SITE_DOMAIN}/new/here/"
    }
  }
}

Then using the config vars, you can point the frontend app to the appropriate backend. To match the original proxy setup:

$ heroku config:set NEW_SITE_DOMAIN="https://example.herokapp.com"

Custom Error Pages

You can replace the default nginx 404 and 500 error pages by defining the path to one in your config.

{
  "error_page": "errors/error.html"
}

HTTPS Only

You can redirect all HTTP requests to HTTPS.

{
  "https_only": true
}

Proxy Backends

For single page web applications like Ember, it's common to back the application with another app that's hosted on Heroku. The down side of separating out these two applications is that now you have to deal with CORS. To get around this (but at the cost of some latency) you can have the static buildpack proxy apps to your backend at a mountpoint. For instance, we can have all the api requests live at /api/ which actually are just requests to our API server.

{
  "proxies": {
    "/api/": {
      "origin": "https://hone-ember-todo-rails.herokuapp.com/"
    }
  }
}

Interpolating Env Var Values

It's common to want to be able to test the frontend against various backends. The origin key supports environment variable substitution using ${ENV_VAR_NAME}. For instance, if there was a staging and production Heroku app for your API, you could setup the config above like the following:

{
  "proxies": {
    "/api/": {
      "origin": "https://${API_APP_NAME}.herokuapp.com/"
    }
  }
}

Then using the config vars, you can point the frontend app to the appropriate backend. To match the original proxy setup:

$ heroku config:set API_APP_NAME="hone-ember-todo-rails"

Custom Headers

Using the headers key, you can set custom response headers. It uses the same operators for pathing as Custom Routes.

{
  "headers": {
    "/": {
      "Cache-Control": "no-store, no-cache"
    },
    "/assets/**": {
      "Cache-Control": "public, max-age=512000"
    },
    "/assets/webfonts/*": {
      "Access-Control-Allow-Origin": "*"
    }
  }
}

For example, to enable CORS for all resources, you just need to enable it for all routes like this:

{
  "headers": {
    "/**": {
      "Access-Control-Allow-Origin": "*"
    }
  }
}

Precedence

When there are header conflicts, the last header definition always wins. The headers do not get appended. For example,

{
  "headers": {
    "/**": {
      "X-Foo": "bar",
      "X-Bar": "baz"
    },
    "/foo": {
      "X-Foo": "foo"
    }
  }
}

when accessing /foo, X-Foo will have the value "foo" and X-Bar will not be present.

Route Ordering

• HTTPS redirect
• Root Files
• Clean URLs
• Proxies
• Redirects
• Custom Routes
• 404

Testing

For testing we use Docker to replicate Heroku locally. You'll need to have it setup locally. We're also using rspec for testing with Ruby. You'll need to have those setup and install those deps:

$ bundle install

To run the test suite just execute:

$ bundle exec rspec

Structure

To add a new test, add another example inside spec/simple_spec.rb or create a new file based off of spec/simple_spec.rb. All the example apps live in spec/fixtures.

When writing a test, BuildpackBuilder creates the docker container we need that represents the heroku cedar-14 stack. AppRunner.new takes the name of a fixture and mounts it in the container built by BuildpackBuilder to run tests against. The AppRunner instance provides convenience methods like get that just wrap net/http for analyzing the response.

Boot2docker

If you are running docker with boot2docker, the buildpack will automatically send tests to the right ip address. You need to forward the docker's port 3000 to the virtual machine's port though.

VBoxManage modifyvm "boot2docker-vm" --natpf1 "tcp-port3000,tcp,,3000,,3000";