Python module for interacting with rtorrent's XML-RPC interface directly over SCGI.

rtorrent_xmlrpc.py

#!/usr/bin/python

# rtorrent_xmlrpc
# (c) 2011 Roger Que <[email protected]>
#
# Python module for interacting with rtorrent's XML-RPC interface
# directly over SCGI, instead of through an HTTP server intermediary.
# Inspired by Glenn Washburn's xmlrpc2scgi.py [1], but subclasses the
# built-in xmlrpclib classes so that it is compatible with features
# such as MultiCall objects.
#
# [1] <http://libtorrent.rakshasa.no/wiki/UtilsXmlrpc2scgi>
#
# Usage: server = SCGIServerProxy('scgi://localhost:7000/')
#        server = SCGIServerProxy('scgi:///path/to/scgi.sock')
#        print server.system.listMethods()
#        mc = xmlrpclib.MultiCall(server)
#        mc.get_up_rate()
#        mc.get_down_rate()
#        print mc()
#
#
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#
# In addition, as a special exception, the copyright holders give
# permission to link the code of portions of this program with the
# OpenSSL library under certain conditions as described in each
# individual source file, and distribute linked combinations
# including the two.
#
# You must obey the GNU General Public License in all respects for
# all of the code used other than OpenSSL.  If you modify file(s)
# with this exception, you may extend this exception to your version
# of the file(s), but you are not obligated to do so.  If you do not
# wish to do so, delete this exception statement from your version.
# If you delete this exception statement from all source files in the
# program, then also delete it here.
#
#
#
# Portions based on Python's xmlrpclib:
#
# Copyright (c) 1999-2002 by Secret Labs AB
# Copyright (c) 1999-2002 by Fredrik Lundh
#
# By obtaining, using, and/or copying this software and/or its
# associated documentation, you agree that you have read, understood,
# and will comply with the following terms and conditions:
#
# Permission to use, copy, modify, and distribute this software and
# its associated documentation for any purpose and without fee is
# hereby granted, provided that the above copyright notice appears in
# all copies, and that both that copyright notice and this permission
# notice appear in supporting documentation, and that the name of
# Secret Labs AB or the author not be used in advertising or publicity
# pertaining to distribution of the software without specific, written
# prior permission.
#
# SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
# TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT-
# ABILITY AND FITNESS.  IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR
# BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY
# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
# OF THIS SOFTWARE.

import re
import socket
import urllib
import xmlrpclib


class SCGITransport(xmlrpclib.Transport):
    def single_request(self, host, handler, request_body, verbose=0):
        # Add SCGI headers to the request.
        headers = {'CONTENT_LENGTH': str(len(request_body)), 'SCGI': '1'}
        header = '\x00'.join(('%s\x00%s' % item for item in headers.iteritems())) + '\x00'
        header = '%d:%s' % (len(header), header)
        request_body = '%s,%s' % (header, request_body)
        
        sock = None
        
        try:
            if host:
                host, port = urllib.splitport(host)
                addrinfo = socket.getaddrinfo(host, port, socket.AF_INET,
                                              socket.SOCK_STREAM)
                sock = socket.socket(*addrinfo[0][:3])
                sock.connect(addrinfo[0][4])
            else:
                sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
                sock.connect(handler)
            
            self.verbose = verbose
            
            sock.send(request_body)
            return self.parse_response(sock.makefile())
        finally:
            if sock:
                sock.close()
    
    def parse_response(self, response):
        p, u = self.getparser()
        
        response_body = ''
        while True:
            data = response.read(1024)
            if not data:
                break
            response_body += data
        
        # Remove SCGI headers from the response.
        response_header, response_body = re.split(r'\n\s*?\n', response_body,
                                                  maxsplit=1)
        
        if self.verbose:
            print 'body:', repr(response_body)
        
        p.feed(response_body)
        p.close()
        
        return u.close()


class SCGIServerProxy(xmlrpclib.ServerProxy):
    def __init__(self, uri, transport=None, encoding=None, verbose=False,
                 allow_none=False, use_datetime=False):
        type, uri = urllib.splittype(uri)
        if type not in ('scgi'):
            raise IOError('unsupported XML-RPC protocol')
        self.__host, self.__handler = urllib.splithost(uri)
        if not self.__handler:
            self.__handler = '/'
        
        if transport is None:
            transport = SCGITransport(use_datetime=use_datetime)
        self.__transport = transport
        
        self.__encoding = encoding
        self.__verbose = verbose
        self.__allow_none = allow_none
 
    def __close(self):
        self.__transport.close()
    
    def __request(self, methodname, params):
        # call a method on the remote server
    
        request = xmlrpclib.dumps(params, methodname, encoding=self.__encoding,
                                  allow_none=self.__allow_none)
    
        response = self.__transport.request(
            self.__host,
            self.__handler,
            request,
            verbose=self.__verbose
            )
    
        if len(response) == 1:
            response = response[0]
    
        return response
    
    def __repr__(self):
        return (
            "<SCGIServerProxy for %s%s>" %
            (self.__host, self.__handler)
            )
    
    __str__ = __repr__
    
    def __getattr__(self, name):
        # magic method dispatcher
        return xmlrpclib._Method(self.__request, name)

    # note: to call a remote object with an non-standard name, use
    # result getattr(server, "strange-python-name")(args)

    def __call__(self, attr):
        """A workaround to get special attributes on the ServerProxy
           without interfering with the magic __getattr__
        """
        if attr == "close":
            return self.__close
        elif attr == "transport":
            return self.__transport
        raise AttributeError("Attribute %r not found" % (attr,))

Nice! Please note a random problem with headers created using dictionary. Order of keys not guaranteed by single_request( self, host, handler, request, verbose = 0 ). rtorrent checks beginning of request buffer always at current (offset = 0). CONTENT_LENGTH must always be first key in dictionary. Better to use OrderedDictionary.

https://gist.github.com/query/899683#file-rtorrent_xmlrpc-py line 90:
headers = {'CONTENT_LENGTH': str(len(request_body)), 'SCGI': '1'}

https://github.com/rakshasa/rtorrent/blob/master/src/rpc/scgi_task.cc line 143):
if (std::memcmp(current, "CONTENT_LENGTH", 15) != 0)
goto event_read_failed;

Also the response_body length should be verified as non-zero and raise a BrokenPipeError exception so that xmlrpc client script will retry upon failure.

See parse_response( self, response )

Very nice. This is exactly what I have been looking for. Thank you :)