post past :: james murty

Amazon has added a new service to their arsenal. CloudFront is a content delivery service that works closely with S3 to make public objects in your account available through a distribution network with edge locations in the US, Europe and Asia.

CloudFront uses two techniques to deliver your data quickly. It caches S3 objects in the network’s edge locations (for a configurable amount of time), and automatically routes incoming requests to the edge location nearest to the requester. If you provide content to people who are distant from an S3 server location, this new service could significantly improve download speeds for your users.

The price for distribution is based on the amount of data transferred and the number of requests, with differential pricing depending on the edge location that serves the content. Bear in mind that you will also incur the standard S3 service costs whenever an object is provided to an edge location.

It is straight-forward to create a CloudFront “distribution” based on one of your S3 buckets. The AWS blog announcement mentions a number of tools and libraries that include support for the new service. My own JetS3t Java library has also been updated with basic API support for the new service, though for now you will need to download the latest code from CVS to access this feature. If you are keen to get your hands dirty, go get a CVS checkout and review the sample code in org.jets3t.samples.CloudFrontSamples.

Inevitably, there are some drawbacks to the service:

• Only publicly readable objects can be distributed through CloudFront, so you cannot use access control settings or temporary signed URLs to limit content delivery to specific people.
• You cannot manually (or programmatically) expire objects at an edge location once they have been cached. Be careful to use appropriate caching directives if you intend to update or remove distributed objects.
• You cannot set a cache expiry time less than 24 hours, so the service is not appropriate for data that is frequently updated.
• As with S3, there is no way to display a default index.html page when someone requests the root location of your CloudFront distribution. This makes it difficult to use the service as a complete replacement for a web server.
• There is currently no support for request logging, though account and usage reports are available.
• There is not yet an edge location close to my Australian home

Despite these drawbacks, CloudFront is a very promising new tool for anyone who needs to distribute a lot of content to a broad audience.