class Rack::Deflater

This middleware enables content encoding of http responses, usually for purposes of compression.

Currently supported encodings:

This middleware automatically detects when encoding is supported and allowed. For example no encoding is made when a cache directive of 'no-transform' is present, when the response status code is one that doesn't allow an entity body, or when the body is empty.

Note that despite the name, Deflater does not support the deflate encoding.

Public Class Methods

new(app, options = {}) click to toggle source

Creates Rack::Deflater middleware. Options:

:if

a lambda enabling / disabling deflation based on returned boolean value (e.g use Rack::Deflater, :if => lambda { |*, body| sum=0; body.each { |i| sum += i.length }; sum > 512 }). However, be aware that calling `body.each` inside the block will break cases where `body.each` is not idempotent, such as when it is an IO instance.

:include

a list of content types that should be compressed. By default, all content types are compressed.

:sync

determines if the stream is going to be flushed after every chunk. Flushing after every chunk reduces latency for time-sensitive streaming applications, but hurts compression and throughput. Defaults to true.

# File lib/rack/deflater.rb, line 35
def initialize(app, options = {})
  @app = app
  @condition = options[:if]
  @compressible_types = options[:include]
  @sync = options.fetch(:sync, true)
end

Public Instance Methods

call(env) click to toggle source 
# File lib/rack/deflater.rb, line 42
def call(env)
  status, headers, body = @app.call(env)
  headers = Utils::HeaderHash[headers]

  unless should_deflate?(env, status, headers, body)
    return [status, headers, body]
  end

  request = Request.new(env)

  encoding = Utils.select_best_encoding(%w(gzip identity),
                                        request.accept_encoding)

  # Set the Vary HTTP header.
  vary = headers["Vary"].to_s.split(",").map(&:strip)
  unless vary.include?("*") || vary.include?("Accept-Encoding")
    headers["Vary"] = vary.push("Accept-Encoding").join(",")
  end

  case encoding
  when "gzip"
    headers['Content-Encoding'] = "gzip"
    headers.delete(CONTENT_LENGTH)
    mtime = headers["Last-Modified"]
    mtime = Time.httpdate(mtime).to_i if mtime
    [status, headers, GzipStream.new(body, mtime, @sync)]
  when "identity"
    [status, headers, body]
  when nil
    message = "An acceptable encoding for the requested resource #{request.fullpath} could not be found."
    bp = Rack::BodyProxy.new([message]) { body.close if body.respond_to?(:close) }
    [406, { CONTENT_TYPE => "text/plain", CONTENT_LENGTH => message.length.to_s }, bp]
  end
end

Private Instance Methods

should_deflate?(env, status, headers, body) click to toggle source

Whether the body should be compressed.

# File lib/rack/deflater.rb, line 121
def should_deflate?(env, status, headers, body)
  # Skip compressing empty entity body responses and responses with
  # no-transform set.
  if Utils::STATUS_WITH_NO_ENTITY_BODY.key?(status.to_i) ||
      /\bno-transform\b/.match?(headers['Cache-Control'].to_s) ||
      headers['Content-Encoding']&.!~(/\bidentity\b/)
    return false
  end

  # Skip if @compressible_types are given and does not include request's content type
  return false if @compressible_types && !(headers.has_key?('Content-Type') && @compressible_types.include?(headers['Content-Type'][/[^;]*/]))

  # Skip if @condition lambda is given and evaluates to false
  return false if @condition && !@condition.call(env, status, headers, body)

  # No point in compressing empty body, also handles usage with
  # Rack::Sendfile.
  return false if headers[CONTENT_LENGTH] == '0'

  true
end