rev: avoid unnecessary seeking when using sendfile

There's no need to ever change the underlying offset of a file
descriptor when using sendfile(), so don't.  This allows us to
avoid contention in the kernel/filesystem and eventually reuse
the same filesystem file descriptor for serving multiple
requests.

2 files changed, 17 insertions, 1 deletions

diff --git a/lib/rainbows/rev/client.rb b/lib/rainbows/rev/client.rb
index 68b3847..e0572bb 100644
--- a/lib/rainbows/rev/client.rb
+++ b/lib/rainbows/rev/client.rb
@@ -86,6 +86,7 @@ module Rainbows
         elsif st.file?
           headers.delete('Transfer-Encoding')
           headers['Content-Length'] ||= st.size.to_s
+          io = to_sendfile(io)
         else # char/block device, directory, whatever... nobody cares
           return write_response(self, response, out)
         end
diff --git a/lib/rainbows/rev/sendfile.rb b/lib/rainbows/rev/sendfile.rb
index 9ab28bd..03ce41c 100644
--- a/lib/rainbows/rev/sendfile.rb
+++ b/lib/rainbows/rev/sendfile.rb
@@ -1,13 +1,28 @@
 # -*- encoding: binary -*-
 module Rainbows::Rev::Sendfile
   if IO.method_defined?(:sendfile_nonblock)
+    class F < Struct.new(:offset, :to_io)
+      def close
+        to_io.close
+        self.to_io = nil
+      end
+    end
+
+    def to_sendfile(io)
+      F[0, io]
+    end
+
     def rev_sendfile(body)
-      body.pos += @_io.sendfile_nonblock(body, body.pos, 0x10000)
+      body.offset += @_io.sendfile_nonblock(body, body.offset, 0x10000)
       rescue Errno::EAGAIN
       ensure
         enable_write_watcher
     end
   else
+    def to_sendfile(io)
+      io
+    end
+
     def rev_sendfile(body)
       write(body.sysread(0x4000))
     end