#AWS Deliver Custom Content With CloudFront

Amazon CloudFront connects with other members of the
AWS Family of services to deliver content to end users
at high speed and with low latency. In order to get started with CloudFront, you simply create
a Distribution, point it at a static or dynamic Origin
running on an service such as S3 or
EC2 or your custom origin, and make use
of the URLs provided to you as part of the Distribution.

Today we are enhancing CloudFront with a new feature that will allow you to
customize or personalize the dynamic content that you deliver to your users.

You can now use additional characteristics of the end user request,
such as their location or the device that they use, to decide what
content to return. These characteristics are passed from CloudFront to
your origin server in the form of HTTP headers. Any headers
added by CloudFront will be prefixed with CloudFront-.

Header Power!
Making additional headers available to your origin server means that your application
can now make choices that are more fully informed by the overall context of the
request. Here are some examples of what can be done:

  • Mobile Device Detection – You can use the User Agent header to
    identify and discriminate between desktop and mobile devices, and to provide content
    that is suitable for and appropriate to each one. CloudFront will also match the header
    against an internal device list and will send an CloudFront-Is-Mobile-Viewer,
    CloudFront-Is-Desktop-Viewer, or CloudFront-Is-Tablet-Viewer
    header to give you a generic indication of the device type.
  • Geo-Targeting – CloudFront will detect the user’s country of origin
    and pass along the county code to you in the CloudFront-Viewer-Country header.
    You can use this information to customize your responses without having to use URLs that are specific
    to each country.
  • Multi-Site Hosting
    CloudFront can now be configured to pass the Host header along to your
    origin server so that you can host multiple web sites and have CloudFront cache
    responses that are specific to each site.
  • Protocol Detection
    You can deliver distinct content to users based on the protocol (HTTP or HTTPS)
    that they use to access your site. This information is available to your
    origin server in the CloudFront-Forwarded-Proto header.
  • CORS (Cross Origin Resource Sharing)
    CloudFront can now be used to deliver web assets such as JavaScript and fonts to
    other websites. Because CloudFront can now be configured to pass the
    Origin header along to the origin server, you can now use
    to allow cross-origin access to your content.

How it Works
Each of your CloudFront distributions now contains a list of headers that are to be
forwarded to the origin server. You have three options:

  • None – This option requests the original behavior.
  • All – This option forwards all headers and effectively disables all
    caching at the edge.
  • Whitelist – This option give you full control of the headers that are
    to be forwarded. The list starts out empty, and grows as you add more headers. You can add
    common HTTP headers by choosing them from a list. You can also add “custom” headers by simply
    entering the name.

If you choose the Whitelist option, each header
that you add to the list becomes part of the cache key
for the URLs associated with the distribution. Adding a header
to the list simply tells CloudFront that the value of the
header can affect the content returned by the origin server.

Let’s say you add Accept-Language to the list of forwarded
headers. This has two important effects. First, your origin server
will have access to the language, and can return content in that
language. Second, the value of the header becomes part of the cache
key. In other words, each edge node will be able to cache the
content specific to the language or languages in the geographic
vicinity of the node.

You should exercise care when adding new headers to the list. Adding
too many headers has the potential to reduce the hit rate for the
cache in the edge node; this will result in additional traffic to
your origin server.

If you are using CloudFront in conjunction with S3, you can now choose to
forward the Origin header. If you do this, you can
use a CORS policy to share the same content between multiple websites.

Getting Started
You can manage your headers from the
CloudFront API or the
AWS Management Console.

Here is how you manage your headers from the console:


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