Tie socket write buffer size to server parameters

By default, Python 2.*'s standard library "socket" module performs 8K
writes. For 10ge networks, with large MTUs (typically 9,000), this is
not optimal. We tie the default buffer size to the client_chunk_size
paramter for the proxy server, and to the network_chunk_size for the
object server.

One might be tempted to ask, isn't there a way to set this value on a
per-request basis? This author was unable to find a reference to the
_fileobject in the context of WSGI. By the time a request pass to a
WSGI object's __call__ method, the "wfile" attribute of the
req.environ['eventlet.input'] (Input) object has been set to None, and
the "rfile" attribute is the object wrapping the socket for reading,
not writing.

One might also be tempted to ask, why not just override the
wsgi.HttpProtocol's "wbufsize" class attribute instead? Until
eventlet/wsgi.py is fixed, we can't set wsgi.HttpProtocol.wbufsize to
anything but zero (the default, see Python's SocketServer.py,
StreamRequestHandler class), since Eventlet does not ensure the socket
_fileobject's flush() method is called after Eventlet invokes a
write() method on the same.  NOTE: wbufsize (a class attribute of
StreamRequestHandler originally, not to be confused with the standard
library's socket._fileobject._wbufsize class attribute) is used for
the bufsize parameter of the connection object's makefile() method. As
a result, the socket's _fileobject code uses that value to set both
_rbufsize and _wbufsize. While that would allow us to transmit in 64KB
chunks, it also means that write() and writeline() method calls on the
socket _fileobject are only transmitted once 64KB have been
accumulated, or a flush() is called.

As for performance improvement:

Run       8KB   64KB
  0     8.101  6.367
  1     7.892  6.216
  2     7.732  6.246
  3     7.594  6.229
  4     7.594  6.292
  5     7.555  6.230
  6     7.575  6.270
  7     7.528  6.278
  8     7.547  6.304
  9     7.550  6.313
Average 7.667  6.275  1.3923  18.16%

Run using the following after adjusting the test value for obj_len to
1 GB:

nosetests -v --nocapture --nologcapture \
test/unit/proxy/test_server.py:TestProxyObjectPerformance.test_GET_debug_large_file

Change-Id: I4dd93acc3376e9960fbdcdcae00c6d002e545894
Signed-off-by: Peter Portante <peter.portante@redhat.com>
Merge "Tie socket write buffer size to server parameters"