Use TCP_CORK to improve throughput for large file transfers

src/calibre/srv/http.py

@@ -553,8 +553,8 @@ class HTTPPair(object):
                 self.simple_response(httplib.PRECONDITION_FAILED)
             return
 
+        with self.conn.corked:
             self.send_headers()
-
             if self.method != 'HEAD':
                 output.commit(self.conn.socket_file)
             self.conn.socket_file.flush()

src/calibre/srv/loop.py

@@ -15,7 +15,7 @@ from io import DEFAULT_BUFFER_SIZE, BytesIO
 from calibre.srv.errors import NonHTTPConnRequest, MaxSizeExceeded
 from calibre.srv.http import http_communicate
 from calibre.srv.opts import Options
-from calibre.srv.utils import socket_errors_to_ignore, socket_error_eintr, socket_errors_nonblocking
+from calibre.srv.utils import socket_errors_to_ignore, socket_error_eintr, socket_errors_nonblocking, Corked
 from calibre.utils.socket_inheritance import set_socket_inherit
 from calibre.utils.logging import ThreadSafeLog
 
@@ -330,6 +330,7 @@ class Connection(object):  # {{{
     def __init__(self, server_loop, socket):
         self.server_loop = server_loop
         self.socket = socket
+        self.corked = Corked(socket)
         self.socket_file = SocketFile(socket)
 
     def nonhttp_communicate(self, data):

src/calibre/srv/utils.py

@@ -6,7 +6,7 @@ from __future__ import (unicode_literals, division, absolute_import,
 __license__ = 'GPL v3'
 __copyright__ = '2015, Kovid Goyal <kovid at kovidgoyal.net>'
 
-import errno
+import errno, socket
 from urlparse import parse_qs
 import repr as reprlib
 from email.utils import formatdate
@@ -107,4 +107,17 @@ socket_errors_to_ignore = error_codes(  # errors indicating a closed connection
 socket_errors_nonblocking = error_codes(
     'EAGAIN', 'EWOULDBLOCK', 'WSAEWOULDBLOCK')
 
+class Corked(object):
 
+    ' Context manager to turn on TCP corking. Ensures maximum throughput for large logical packets. '
+
+    def __init__(self, sock):
+        self.sock = sock if hasattr(socket, 'TCP_CORK') else None
+
+    def __enter__(self):
+        if self.sock is not None:
+            self.sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_CORK, 1)
+
+    def __exit__(self, *args):
+        if self.sock is not None:
+            self.sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_CORK, 0)