Send HTTP requests with a single send() call instead of many.

The implementation now stores all the lines of the request in a buffer
and makes a single send() call when the request is finished,
specifically when endheaders() is called.

This appears to improve performance.  The old code called send() for
each line.  The sends are all short, so they caused bad interactions
with the Nagle algorithm and delayed acknowledgements.  In simple
tests, the second packet was delayed by 100s of ms.  The second send was
delayed by the Nagle algorithm, waiting for the ack.  The delayed ack
strategy delays the ack in hopes of piggybacking it on a data packet,
but the server won't send any data until it receives the complete
request.

This change minimizes the problem that Nagle + delayed ack will cause
a problem, although a request large enough to be broken into two
packets will still suffer some delay.  Luckily the MSS is large enough
to accomodate most single packets.

XXX Bug fix candidate?

1 files changed, 26 insertions, 15 deletions

diff --git a/Lib/httplib.py b/Lib/httplib.py
index 34ed2da..d9fd6dd 100644
--- a/Lib/httplib.py
+++ b/Lib/httplib.py
@@ -479,6 +479,7 @@ class HTTPConnection:
 
     def __init__(self, host, port=None, strict=None):
         self.sock = None
+        self._buffer = []
         self.__response = None
         self.__state = _CS_IDLE
         
@@ -543,7 +544,7 @@ class HTTPConnection:
             else:
                 raise NotConnected()
 
-        # send the data to the server. if we get a broken pipe, then close
+        # send the data to the server. if we get a broken pipe, then closesdwu
         # the socket. we want to reconnect when somebody tries to send again.
         #
         # NOTE: we DO propagate the error, though, because we cannot simply
@@ -557,6 +558,23 @@ class HTTPConnection:
                 self.close()
             raise
 
+    def _output(self, s):
+        """Add a line of output to the current request buffer.
+        
+        Aassumes that the line does *not* end with \r\n.
+        """
+        self._buffer.append(s)
+
+    def _send_output(self):
+        """Send the currently buffered request and clear the buffer.
+
+        Appends an extra \r\n to the buffer.
+        """
+        self._buffer.extend(("", ""))
+        msg = "\r\n".join(self._buffer)
+        del self._buffer[:]
+        self.send(msg)
+
     def putrequest(self, method, url, skip_host=0):
         """Send a request to the server.
 
@@ -565,6 +583,7 @@ class HTTPConnection:
         """
 
         # check if a prior response has been completed
+        # XXX What if it hasn't?
         if self.__response and self.__response.isclosed():
             self.__response = None
 
@@ -594,16 +613,9 @@ class HTTPConnection:
 
         if not url:
             url = '/'
-        str = '%s %s %s\r\n' % (method, url, self._http_vsn_str)
+        str = '%s %s %s' % (method, url, self._http_vsn_str)
 
-        try:
-            self.send(str)
-        except socket.error, v:
-            # trap 'Broken pipe' if we're allowed to automatically reconnect
-            if v[0] != 32 or not self.auto_open:
-                raise
-            # try one more time (the socket was closed; this will reopen)
-            self.send(str)
+        self._output(str)
 
         if self._http_vsn == 11:
             # Issue some standard headers for better HTTP/1.1 compliance
@@ -664,8 +676,8 @@ class HTTPConnection:
         if self.__state != _CS_REQ_STARTED:
             raise CannotSendHeader()
 
-        str = '%s: %s\r\n' % (header, value)
-        self.send(str)
+        str = '%s: %s' % (header, value)
+        self._output(str)
 
     def endheaders(self):
         """Indicate that the last header line has been sent to the server."""
@@ -675,7 +687,7 @@ class HTTPConnection:
         else:
             raise CannotSendHeader()
 
-        self.send('\r\n')
+        self._send_output()
 
     def request(self, method, url, body=None, headers={}):
         """Send a complete request to the server."""
@@ -1202,6 +1214,7 @@ def test():
                                ):
             print "https://%s%s" % (host, selector)
             hs = HTTPS()
+            hs.set_debuglevel(dl)
             hs.connect(host)
             hs.putrequest('GET', selector)
             hs.endheaders()
@@ -1214,8 +1227,6 @@ def test():
                 for header in headers.headers: print header.strip()
             print
 
-    return
-
     # Test a buggy server -- returns garbled status line.
     # http://www.yahoo.com/promotions/mom_com97/supermom.html
     c = HTTPConnection("promotions.yahoo.com")