Middleman::S3Sync

This gem determines which files need to be added, updated and optionally deleted and only transfer these files up. This reduces the impact of an update on a web site hosted on S3.

Why not Middleman Sync?

Middleman Sync does a great job to push Middleman generated websites to S3. The only issue I have with it is that it pushes every files under build to S3 and doesn't seem to properly delete files that are no longer needed.

Installation

Add this line to your application's Gemfile:

gem 'middleman-s3_sync'

And then execute:

$ bundle

Or install it yourself as:

$ gem install middleman-s3_sync

Usage

You need to add the following code to your config.rb file:

activate :s3_sync do |s3_sync|
  s3_sync.bucket                = 'my.bucket.com' # The name of the S3 bucket you are targetting. This is globally unique.
  s3_sync.region                = 'us-west-1'     # The AWS region for your bucket.
  s3_sync.aws_access_key_id     = 'AWS KEY ID'
  s3_sync.aws_secret_access_key = 'AWS SECRET KEY'
  s3_sync.delete                = false # We delete stray files by default.
  s3_sync.after_build           = false # We chain after the build step by default. This may not be your desired behavior...
  s3_sync.prefer_gzip           = true
end

You can then start synchronizing files with S3 through middleman s3_sync.

Configuration Defaults

The following defaults apply to the configuration items:

Setting	Default
aws_access_key_id	ENV['AWS_ACCESS_KEY_ID
aws_secret_access_key	ENV['AWS_SECRET_ACCESS_KEY']
delete	true
after_build	false
prefer_gzip	true

You do not need to specify the settings that match the defaults. This simplify the configuration of the extension:

activate :s3_sync do |s3_sync|
  s3_sync.bucket = 'my.bucket.com'
end

Push All Content to S3

There are situations where you might need to push the files to S3. In such case, you can pass the --force option:

$ middleman s3_sync --force

Overriding the destination bucket

You can now override the destination bucket using the --bucket switch. The command is:

$ middleman s3_sync --bucket=my.new.bucket

HTTP Caching

By default, middleman-s3_sync does not set caching headers. In general, the default settings are sufficient. However, there are situations where you might want to set a different HTTP caching policy. This may be very helpful if you are using the asset_hash extension.

Setting a policy based on the mime-type of a file

You can set a caching policy for every files that match a certain mime-type. For example, setting max-age to 0 and kindly asking the browser to revalidate the content for HTML files would take the following form:

caching_policy 'text/html', max_age: 0, must_revalidate: true

As a result, the following Cache-Control header would be set to max-age:0, must-revalidate

Setting a Default Policy

You can set the default policy by passing an options hash to default_caching_policy in your config.rb file:

default_caching_policy max_age:(60 * 60 * 24 * 365)

This will apply the policy to any file that do not have a mime-type specific policy.

Caching Policies

The Caching Tutorial is a great introduction to HTTP caching. The caching policy code in this gem is based on it.

The following keys can be set:

Key	Value	Header	Description
max_age	seconds	max-age	Specifies the maximum amount of time that a representation will be considered fresh. This value is relative to the time of the request
s_maxage	seconds	s-maxage	Only applies to shared (proxies) caches
public	boolean	public	Marks authenticated responses as cacheable.
private	boolean	private	Allows caches that are specific to one user to store the response. Shared caches (proxies) may not.
no_cache	boolean	no-cache	Forces caches to submit the request to the origin server for validation before releasing a cached copy, every time.
no_store	boolean	no-store	Instructs caches not to keep a copy of the representation under any conditions.
must_revalidate	boolean	must-revalidate	Tells the caches that they must obey any freshness information you give them about a representation.
proxy_revalidate	boolean	proxy-revalidate	Similar as must-revalidate, but only for proxies.

Setting Expires Header

You can pass the expires key to the caching_policy and default_caching_policy methods if you insist on setting the expires header on a results. You will need to pass it a Time object indicating when the resourse is set to expire.

Note that the Cache-Control header will take precedence over the Expires header if both are present.

A Note About Browser Caching

Browser caching is well specified. It hasn't always been the case. Still, even modern browsers have different behaviors if it suits it's developers or their employers. Specs are meant to be ignored and so they are (I'm looking at you Chrome!). Setting the Cache-Control or Expires headers are not a guarrantie that the browsers and the proxies that stand between them and your content will behave the way you want them to. YMMV.

GZipped Content Encoding

You can set the prefer_gzip option to look for a gzipped version of a resource. The gzipped version of the resource will be pushed to S3 instead of the original and the Content-Encoding and Content-Type headers will be set correctly. This will cause Amazon to serve the compressed version of the resource.

A Debt of Gratitude

I used Middleman Sync as a template for building a Middleman extension. The code is well structured and easy to understand and it was easy to extend it to add my synchronization code. My gratitude goes to @karlfreeman and is work on Middleman sync.

Many thanks to Gnip and dojo4 for supporting and sponsoring work on middleman-s3_sync.

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request