HTTP Compression in Rails

Caleb Woods

RoleModel Software

Reasons for compression

Mobile Device Client
Low Bandwidth Environment
Performance

Problem Environment

iOS app connecting to a Rails backed API
Large requests (response body ~ 230 kb)
Large downloads, hundreds of requests

Solution

Gzip compression

Widely supported
Easy to use in both Rails and iOS

Gzipped Responses

Rack Deflater

Built into Rack
Accept-Encoding: gzip header

# application.rb config.middleware.use Rack::Deflater

Gzipped Requests

Custom Mime Type
Use ActiveSupport::Gzip to decompress the request

# config/initializers/mime_types.rb Mime::Type.register "gizp/json", :gzipjson ActionDispatch::ParamsParser::DEFAULT_PARSERS[Mime::Type.lookup('gzip/json')]=lambda do |raw_body| body = ActiveSupport::Gzip.decompress(raw_body) JSON.parse(body).with_indifferent_access end

Testing

# rack_deflater_spec.rb require 'spec_helper' describe Rack::Deflater do include_context 'API' it "encodes response if requested" do api_get "posts" response.headers["Content-Encoding"].should be_nil content_length = response.headers["Content-Length"].to_i api_get_gzipped "posts" response.headers["Content-Length"].to_i.should <= content_length response.headers["Content-Encoding"].should == "gzip" end it "accepts gzip encoded data" do api_post_gziped "posts", post: { name: 'Compressed' } response.headers["Content-Encoding"].should == "gzip" response.status.should eq 201 decompressed_json_body.should include 'name' => 'Compressed' end end

Results

~90% response size decrease
40% speed increase iOS app large downloads

iOS Tools

AFNetworking
- Automatically decompresses Gzipped responses
Godzippa
- Must be properly configured to used Gzip