Add `:use_accelerate_endpoint` option when using S3

[Amazon S3 Transfer
Acceleration](http://docs.aws.amazon.com/AmazonS3/latest/dev/transfer-acceleration.html)
enables fast, easy, and secure transfers of files over long distances
between your client and an S3 bucket. And
[aws-sdk](https://github.com/aws/aws-sdk-ruby) has allowed us to enable
this feature in version 2.3.0 (more detail is
[here](https://github.com/aws/aws-sdk-ruby/pull/1163)).

You can now pass a configuration option (:use_accelerate_endpoint) when
config Paperclip with S3. You can enable the [Amazon S3 Transfer
Acceleration](http://docs.aws.amazon.com/AmazonS3/latest/dev/transfer-acceleration.html)
by set this option:
```:use_accelerate_endpoint => true```

[fixes #2291]

NEWS

 master:
 
+* Improvement: Added `:use_accelerate_endpoint` option when using S3 to enable
+  [Amazon S3 Transfer Acceleration](http://docs.aws.amazon.com/AmazonS3/latest/dev/transfer-acceleration.html)
 * Improvement: make the fingerprint digest configurable per attachment. The
   default remains MD5 but this will change in a future version because it is
   not considered secure anymore against intentional file corruption. For more

lib/paperclip/storage/s3.rb

@@ -102,6 +102,8 @@ module Paperclip
     #   Redundancy Storage. RRS enables customers to reduce their
     #   costs by storing non-critical, reproducible data at lower
     #   levels of redundancy than Amazon S3's standard storage.
+    # * +use_accelerate_endpoint+: Use accelerate endpoint
+    #   http://docs.aws.amazon.com/AmazonS3/latest/dev/transfer-acceleration.html
     #
     #   You can set storage class on a per style bases by doing the following:
     #     :s3_storage_class => {
@@ -152,6 +154,13 @@ module Paperclip
           @options[:url] = @options[:url].inspect if @options[:url].is_a?(Symbol)
 
           @http_proxy = @options[:http_proxy] || nil
+
+          if @options.has_key?(:use_accelerate_endpoint) &&
+              Gem::Version.new(Aws::VERSION) < Gem::Version.new("2.3.0")
+            raise LoadError, ":use_accelerate_endpoint is only available from aws-sdk version 2.3.0. Please upgrade aws-sdk to a newer version."
+          end
+
+          @use_accelerate_endpoint = @options[:use_accelerate_endpoint]
         end
 
         Paperclip.interpolates(:s3_alias_url) do |attachment, style|
@@ -232,6 +241,8 @@ module Paperclip
             config[:proxy_uri] = URI::HTTP.build(proxy_opts)
           end
 
+          config[:use_accelerate_endpoint] = use_accelerate_endpoint?
+
           [:access_key_id, :secret_access_key, :credential_provider, :credentials].each do |opt|
             config[opt] = s3_credentials[opt] if s3_credentials[opt]
           end
@@ -257,6 +268,10 @@ module Paperclip
         s3_bucket.object style_name_as_path(style_name)
       end
 
+      def use_accelerate_endpoint?
+        !!@use_accelerate_endpoint
+      end
+
       def using_http_proxy?
         !!@http_proxy
       end

spec/paperclip/storage/s3_spec.rb

@@ -282,6 +282,59 @@ describe Paperclip::Storage::S3 do
     end
   end
 
+  context "use_accelerate_endpoint", if: aws_accelerate_available? do
+    context "defaults to false" do
+      before do
+        rebuild_model(
+          storage: :s3,
+          s3_credentials: {},
+          bucket: "bucket",
+          path: ":attachment/:basename:dotextension",
+          s3_host_name: "s3-ap-northeast-1.amazonaws.com",
+          s3_region: "ap-northeast-1",
+        )
+        @dummy = Dummy.new
+        @dummy.avatar = stringy_file
+        @dummy.stubs(:new_record?).returns(false)
+      end
+
+      it "returns a url based on an :s3_host_name path" do
+        assert_match %r{^//s3-ap-northeast-1.amazonaws.com/bucket/avatars/data[^\.]},
+          @dummy.avatar.url
+      end
+
+      it "uses the S3 client with the use_accelerate_endpoint config is false" do
+        expect(@dummy.avatar.s3_bucket.client.config.use_accelerate_endpoint).to be(false)
+      end
+    end
+
+    context "set to true", if: aws_accelerate_available? do
+      before do
+        rebuild_model(
+          storage: :s3,
+          s3_credentials: {},
+          bucket: "bucket",
+          path: ":attachment/:basename:dotextension",
+          s3_host_name: "s3-accelerate.amazonaws.com",
+          s3_region: "ap-northeast-1",
+          use_accelerate_endpoint: true,
+        )
+        @dummy = Dummy.new
+        @dummy.avatar = stringy_file
+        @dummy.stubs(:new_record?).returns(false)
+      end
+
+      it "returns a url based on an :s3_host_name path" do
+        assert_match %r{^//s3-accelerate.amazonaws.com/bucket/avatars/data[^\.]},
+          @dummy.avatar.url
+      end
+
+      it "uses the S3 client with the use_accelerate_endpoint config is true" do
+        expect(@dummy.avatar.s3_bucket.client.config.use_accelerate_endpoint).to be(true)
+      end
+    end
+  end
+
   context "An attachment that uses S3 for storage and has styles that return different file types" do
     before do
       rebuild_model (aws2_add_region).merge storage: :s3,

spec/spec_helper.rb

@@ -38,6 +38,7 @@ RSpec.configure do |config|
   config.include TestData
   config.include Reporting
   config.extend VersionHelper
+  config.extend ConditionalFilterHelper
   config.mock_framework = :mocha
   config.before(:all) do
     rebuild_model

spec/support/conditional_filter_helper.rb

+module ConditionalFilterHelper
+  def aws_accelerate_available?
+    (Gem::Version.new(Aws::VERSION) >= Gem::Version.new("2.3.0"))
+  end
+end