deflater: support "sync: false" option

Flushing after after very flush is great for real-time apps.
However, flushing is inefficient when apps use Rack::Response
to generate many small writes (e.g.  Rack::Lobster).

Allow users to disable the default "sync: true" behavior to
reduce bandwidth usage, otherwise using Rack::Deflater can lead
to using more bandwidth than without it.

1 files changed, 34 insertions, 0 deletions

diff --git a/test/spec_deflater.rb b/test/spec_deflater.rb
index 0f27c859..410a1438 100644
--- a/test/spec_deflater.rb
+++ b/test/spec_deflater.rb
@@ -372,4 +372,38 @@ describe Rack::Deflater do
 
     verify(200, response, 'gzip', options)
   end
+
+  it 'will honor sync: false to avoid unnecessary flushing' do
+    app_body = Object.new
+    class << app_body
+      def each
+        (0..20).each { |i| yield "hello\n".freeze }
+      end
+    end
+
+    options = {
+      'deflater_options' => { :sync => false },
+      'app_body' => app_body,
+      'skip_body_verify' => true,
+    }
+    verify(200, app_body, deflate_or_gzip, options) do |status, headers, body|
+      headers.must_equal({
+        'Content-Encoding' => 'gzip',
+        'Vary' => 'Accept-Encoding',
+        'Content-Type' => 'text/plain'
+      })
+
+      buf = ''
+      raw_bytes = 0
+      inflater = auto_inflater
+      body.each do |part|
+        raw_bytes += part.bytesize
+        buf << inflater.inflate(part)
+      end
+      buf << inflater.finish
+      expect = "hello\n" * 21
+      buf.must_equal expect
+      raw_bytes.must_be(:<, expect.bytesize)
+    end
+  end
 end