class Rack::Deflater
This middleware enables compression of http responses.
Currently supported compression algorithms:
* gzip * identity (no transformation)
The middleware automatically detects when compression is supported and allowed. For example no transformation is made when a cache directive of 'no-transform' is present, or when the response status code is one that doesn't allow an entity body.
Public Class Methods
new(app, options = {})
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Creates Rack::Deflater
middleware.
- app
-
rack app instance
- options
-
hash of deflater options, i.e. '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 }
'include' - a list of content types that should be 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 36 def initialize(app, options = {}) @app = app @condition = options[:if] @compressible_types = options[:include] @sync = options[:sync] == false ? false : true end
Public Instance Methods
call(env)
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# File lib/rack/deflater.rb, line 44 def call(env) status, headers, body = @app.call(env) headers = Utils::HeaderHash.new(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)
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# File lib/rack/deflater.rb, line 112 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'] && 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) true end