http client: support persistent connections.

uses keepalive module from urlgrabber package.  tested against "hg serve",
cgi server, and through http proxy.  used ethereal to verify that only
one tcp connection used during entire "hg pull" sequence.

if server supports keepalive, this makes latency of "hg pull" much lower.

mercurial/keepalive.py

@@ -0,0 +1,587
+#   This library is free software; you can redistribute it and/or
+#   modify it under the terms of the GNU Lesser General Public
+#   License as published by the Free Software Foundation; either
+#   version 2.1 of the License, or (at your option) any later version.
+#
+#   This library 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
+#   Lesser General Public License for more details.
+#
+#   You should have received a copy of the GNU Lesser General Public
+#   License along with this library; if not, write to the 
+#      Free Software Foundation, Inc., 
+#      59 Temple Place, Suite 330, 
+#      Boston, MA  02111-1307  USA
+
+# This file is part of urlgrabber, a high-level cross-protocol url-grabber
+# Copyright 2002-2004 Michael D. Stenner, Ryan Tomayko
+
+"""An HTTP handler for urllib2 that supports HTTP 1.1 and keepalive.
+
+>>> import urllib2
+>>> from keepalive import HTTPHandler
+>>> keepalive_handler = HTTPHandler()
+>>> opener = urllib2.build_opener(keepalive_handler)
+>>> urllib2.install_opener(opener)
+>>> 
+>>> fo = urllib2.urlopen('http://www.python.org')
+
+If a connection to a given host is requested, and all of the existing
+connections are still in use, another connection will be opened.  If
+the handler tries to use an existing connection but it fails in some
+way, it will be closed and removed from the pool.
+
+To remove the handler, simply re-run build_opener with no arguments, and
+install that opener.
+
+You can explicitly close connections by using the close_connection()
+method of the returned file-like object (described below) or you can
+use the handler methods:
+
+  close_connection(host)
+  close_all()
+  open_connections()
+
+NOTE: using the close_connection and close_all methods of the handler
+should be done with care when using multiple threads.
+  * there is nothing that prevents another thread from creating new
+    connections immediately after connections are closed
+  * no checks are done to prevent in-use connections from being closed
+
+>>> keepalive_handler.close_all()
+
+EXTRA ATTRIBUTES AND METHODS
+
+  Upon a status of 200, the object returned has a few additional
+  attributes and methods, which should not be used if you want to
+  remain consistent with the normal urllib2-returned objects:
+
+    close_connection()  -  close the connection to the host
+    readlines()         -  you know, readlines()
+    status              -  the return status (ie 404)
+    reason              -  english translation of status (ie 'File not found')
+
+  If you want the best of both worlds, use this inside an
+  AttributeError-catching try:
+
+  >>> try: status = fo.status
+  >>> except AttributeError: status = None
+
+  Unfortunately, these are ONLY there if status == 200, so it's not
+  easy to distinguish between non-200 responses.  The reason is that
+  urllib2 tries to do clever things with error codes 301, 302, 401,
+  and 407, and it wraps the object upon return.
+
+  For python versions earlier than 2.4, you can avoid this fancy error
+  handling by setting the module-level global HANDLE_ERRORS to zero.
+  You see, prior to 2.4, it's the HTTP Handler's job to determine what
+  to handle specially, and what to just pass up.  HANDLE_ERRORS == 0
+  means "pass everything up".  In python 2.4, however, this job no
+  longer belongs to the HTTP Handler and is now done by a NEW handler,
+  HTTPErrorProcessor.  Here's the bottom line:
+
+    python version < 2.4
+        HANDLE_ERRORS == 1  (default) pass up 200, treat the rest as
+                            errors
+        HANDLE_ERRORS == 0  pass everything up, error processing is
+                            left to the calling code
+    python version >= 2.4
+        HANDLE_ERRORS == 1  pass up 200, treat the rest as errors
+        HANDLE_ERRORS == 0  (default) pass everything up, let the
+                            other handlers (specifically,
+                            HTTPErrorProcessor) decide what to do
+
+  In practice, setting the variable either way makes little difference
+  in python 2.4, so for the most consistent behavior across versions,
+  you probably just want to use the defaults, which will give you
+  exceptions on errors.
+
+"""
+
+# $Id: keepalive.py,v 1.13 2005/10/22 21:57:28 mstenner Exp $
+
+import urllib2
+import httplib
+import socket
+import thread
+
+DEBUG = None
+
+import sys
+if sys.version_info < (2, 4): HANDLE_ERRORS = 1
+else: HANDLE_ERRORS = 0
+    
+class ConnectionManager:
+    """
+    The connection manager must be able to:
+      * keep track of all existing
+      """
+    def __init__(self):
+        self._lock = thread.allocate_lock()
+        self._hostmap = {} # map hosts to a list of connections
+        self._connmap = {} # map connections to host
+        self._readymap = {} # map connection to ready state
+
+    def add(self, host, connection, ready):
+        self._lock.acquire()
+        try:
+            if not self._hostmap.has_key(host): self._hostmap[host] = []
+            self._hostmap[host].append(connection)
+            self._connmap[connection] = host
+            self._readymap[connection] = ready
+        finally:
+            self._lock.release()
+
+    def remove(self, connection):
+        self._lock.acquire()
+        try:
+            try:
+                host = self._connmap[connection]
+            except KeyError:
+                pass
+            else:
+                del self._connmap[connection]
+                del self._readymap[connection]
+                self._hostmap[host].remove(connection)
+                if not self._hostmap[host]: del self._hostmap[host]
+        finally:
+            self._lock.release()
+
+    def set_ready(self, connection, ready):
+        try: self._readymap[connection] = ready
+        except KeyError: pass
+        
+    def get_ready_conn(self, host):
+        conn = None
+        self._lock.acquire()
+        try:
+            if self._hostmap.has_key(host):
+                for c in self._hostmap[host]:
+                    if self._readymap[c]:
+                        self._readymap[c] = 0
+                        conn = c
+                        break
+        finally:
+            self._lock.release()
+        return conn
+
+    def get_all(self, host=None):
+        if host:
+            return list(self._hostmap.get(host, []))
+        else:
+            return dict(self._hostmap)
+
+class HTTPHandler(urllib2.HTTPHandler):
+    def __init__(self):
+        self._cm = ConnectionManager()
+        
+    #### Connection Management
+    def open_connections(self):
+        """return a list of connected hosts and the number of connections
+        to each.  [('foo.com:80', 2), ('bar.org', 1)]"""
+        return [(host, len(li)) for (host, li) in self._cm.get_all().items()]
+
+    def close_connection(self, host):
+        """close connection(s) to <host>
+        host is the host:port spec, as in 'www.cnn.com:8080' as passed in.
+        no error occurs if there is no connection to that host."""
+        for h in self._cm.get_all(host):
+            self._cm.remove(h)
+            h.close()
+        
+    def close_all(self):
+        """close all open connections"""
+        for host, conns in self._cm.get_all().items():
+            for h in conns:
+                self._cm.remove(h)
+                h.close()
+        
+    def _request_closed(self, request, host, connection):
+        """tells us that this request is now closed and the the
+        connection is ready for another request"""
+        self._cm.set_ready(connection, 1)
+
+    def _remove_connection(self, host, connection, close=0):
+        if close: connection.close()
+        self._cm.remove(connection)
+        
+    #### Transaction Execution
+    def http_open(self, req):
+        return self.do_open(HTTPConnection, req)
+
+    def do_open(self, http_class, req):
+        host = req.get_host()
+        if not host:
+            raise urllib2.URLError('no host given')
+
+        try:
+            h = self._cm.get_ready_conn(host)
+            while h:
+                r = self._reuse_connection(h, req, host)
+
+                # if this response is non-None, then it worked and we're
+                # done.  Break out, skipping the else block.
+                if r: break
+
+                # connection is bad - possibly closed by server
+                # discard it and ask for the next free connection
+                h.close()
+                self._cm.remove(h)
+                h = self._cm.get_ready_conn(host)
+            else:
+                # no (working) free connections were found.  Create a new one.
+                h = http_class(host)
+                if DEBUG: DEBUG.info("creating new connection to %s (%d)",
+                                     host, id(h))
+                self._cm.add(host, h, 0)
+                self._start_transaction(h, req)
+                r = h.getresponse()
+        except (socket.error, httplib.HTTPException), err:
+            raise urllib2.URLError(err)
+            
+        # if not a persistent connection, don't try to reuse it
+        if r.will_close: self._cm.remove(h)
+
+        if DEBUG: DEBUG.info("STATUS: %s, %s", r.status, r.reason)
+        r._handler = self
+        r._host = host
+        r._url = req.get_full_url()
+        r._connection = h
+        r.code = r.status
+        
+        if r.status == 200 or not HANDLE_ERRORS:
+            return r
+        else:
+            return self.parent.error('http', req, r, r.status, r.reason, r.msg)
+
+
+    def _reuse_connection(self, h, req, host):
+        """start the transaction with a re-used connection
+        return a response object (r) upon success or None on failure.
+        This DOES not close or remove bad connections in cases where
+        it returns.  However, if an unexpected exception occurs, it
+        will close and remove the connection before re-raising.
+        """
+        try:
+            self._start_transaction(h, req)
+            r = h.getresponse()
+            # note: just because we got something back doesn't mean it
+            # worked.  We'll check the version below, too.
+        except (socket.error, httplib.HTTPException):
+            r = None
+        except:
+            # adding this block just in case we've missed
+            # something we will still raise the exception, but
+            # lets try and close the connection and remove it
+            # first.  We previously got into a nasty loop
+            # where an exception was uncaught, and so the
+            # connection stayed open.  On the next try, the
+            # same exception was raised, etc.  The tradeoff is
+            # that it's now possible this call will raise
+            # a DIFFERENT exception
+            if DEBUG: DEBUG.error("unexpected exception - closing " + \
+                                  "connection to %s (%d)", host, id(h))
+            self._cm.remove(h)
+            h.close()
+            raise
+                    
+        if r is None or r.version == 9:
+            # httplib falls back to assuming HTTP 0.9 if it gets a
+            # bad header back.  This is most likely to happen if
+            # the socket has been closed by the server since we
+            # last used the connection.
+            if DEBUG: DEBUG.info("failed to re-use connection to %s (%d)",
+                                 host, id(h))
+            r = None
+        else:
+            if DEBUG: DEBUG.info("re-using connection to %s (%d)", host, id(h))
+
+        return r
+
+    def _start_transaction(self, h, req):
+        try:
+            if req.has_data():
+                data = req.get_data()
+                h.putrequest('POST', req.get_selector())
+                if not req.headers.has_key('Content-type'):
+                    h.putheader('Content-type',
+                                'application/x-www-form-urlencoded')
+                if not req.headers.has_key('Content-length'):
+                    h.putheader('Content-length', '%d' % len(data))
+            else:
+                h.putrequest('GET', req.get_selector())
+        except (socket.error, httplib.HTTPException), err:
+            raise urllib2.URLError(err)
+
+        for args in self.parent.addheaders:
+            h.putheader(*args)
+        for k, v in req.headers.items():
+            h.putheader(k, v)
+        h.endheaders()
+        if req.has_data():
+            h.send(data)
+
+class HTTPResponse(httplib.HTTPResponse):
+    # we need to subclass HTTPResponse in order to
+    # 1) add readline() and readlines() methods
+    # 2) add close_connection() methods
+    # 3) add info() and geturl() methods
+
+    # in order to add readline(), read must be modified to deal with a
+    # buffer.  example: readline must read a buffer and then spit back
+    # one line at a time.  The only real alternative is to read one
+    # BYTE at a time (ick).  Once something has been read, it can't be
+    # put back (ok, maybe it can, but that's even uglier than this),
+    # so if you THEN do a normal read, you must first take stuff from
+    # the buffer.
+
+    # the read method wraps the original to accomodate buffering,
+    # although read() never adds to the buffer.
+    # Both readline and readlines have been stolen with almost no
+    # modification from socket.py
+    
+
+    def __init__(self, sock, debuglevel=0, strict=0, method=None):
+        if method: # the httplib in python 2.3 uses the method arg
+            httplib.HTTPResponse.__init__(self, sock, debuglevel, method)
+        else: # 2.2 doesn't
+            httplib.HTTPResponse.__init__(self, sock, debuglevel)
+        self.fileno = sock.fileno
+        self.code = None
+        self._rbuf = ''
+        self._rbufsize = 8096
+        self._handler = None # inserted by the handler later
+        self._host = None    # (same)
+        self._url = None     # (same)
+        self._connection = None # (same)
+
+    _raw_read = httplib.HTTPResponse.read
+
+    def close(self):
+        if self.fp:
+            self.fp.close()
+            self.fp = None
+            if self._handler:
+                self._handler._request_closed(self, self._host,
+                                              self._connection)
+
+    def close_connection(self):
+        self._handler._remove_connection(self._host, self._connection, close=1)
+        self.close()
+        
+    def info(self):
+        return self.msg
+
+    def geturl(self):
+        return self._url
+
+    def read(self, amt=None):
+        # the _rbuf test is only in this first if for speed.  It's not
+        # logically necessary
+        if self._rbuf and not amt is None:
+            L = len(self._rbuf)
+            if amt > L:
+                amt -= L
+            else:
+                s = self._rbuf[:amt]
+                self._rbuf = self._rbuf[amt:]
+                return s
+
+        s = self._rbuf + self._raw_read(amt)
+        self._rbuf = ''
+        return s
+
+    def readline(self, limit=-1):
+        data = ""
+        i = self._rbuf.find('\n')
+        while i < 0 and not (0 < limit <= len(self._rbuf)):
+            new = self._raw_read(self._rbufsize)
+            if not new: break
+            i = new.find('\n')
+            if i >= 0: i = i + len(self._rbuf)
+            self._rbuf = self._rbuf + new
+        if i < 0: i = len(self._rbuf)
+        else: i = i+1
+        if 0 <= limit < len(self._rbuf): i = limit
+        data, self._rbuf = self._rbuf[:i], self._rbuf[i:]
+        return data
+
+    def readlines(self, sizehint = 0):
+        total = 0
+        list = []
+        while 1:
+            line = self.readline()
+            if not line: break
+            list.append(line)
+            total += len(line)
+            if sizehint and total >= sizehint:
+                break
+        return list
+
+
+class HTTPConnection(httplib.HTTPConnection):
+    # use the modified response class
+    response_class = HTTPResponse
+    
+#########################################################################
+#####   TEST FUNCTIONS
+#########################################################################
+
+def error_handler(url):
+    global HANDLE_ERRORS
+    orig = HANDLE_ERRORS
+    keepalive_handler = HTTPHandler()
+    opener = urllib2.build_opener(keepalive_handler)
+    urllib2.install_opener(opener)
+    pos = {0: 'off', 1: 'on'}
+    for i in (0, 1):
+        print "  fancy error handling %s (HANDLE_ERRORS = %i)" % (pos[i], i)
+        HANDLE_ERRORS = i
+        try:
+            fo = urllib2.urlopen(url)
+            foo = fo.read()
+            fo.close()
+            try: status, reason = fo.status, fo.reason
+            except AttributeError: status, reason = None, None
+        except IOError, e:
+            print "  EXCEPTION: %s" % e
+            raise
+        else:
+            print "  status = %s, reason = %s" % (status, reason)
+    HANDLE_ERRORS = orig
+    hosts = keepalive_handler.open_connections()
+    print "open connections:", hosts
+    keepalive_handler.close_all()
+
+def continuity(url):
+    import md5
+    format = '%25s: %s'
+    
+    # first fetch the file with the normal http handler
+    opener = urllib2.build_opener()
+    urllib2.install_opener(opener)
+    fo = urllib2.urlopen(url)
+    foo = fo.read()
+    fo.close()
+    m = md5.new(foo)
+    print format % ('normal urllib', m.hexdigest())
+
+    # now install the keepalive handler and try again
+    opener = urllib2.build_opener(HTTPHandler())
+    urllib2.install_opener(opener)
+
+    fo = urllib2.urlopen(url)
+    foo = fo.read()
+    fo.close()
+    m = md5.new(foo)
+    print format % ('keepalive read', m.hexdigest())
+
+    fo = urllib2.urlopen(url)
+    foo = ''
+    while 1:
+        f = fo.readline()
+        if f: foo = foo + f
+        else: break
+    fo.close()
+    m = md5.new(foo)
+    print format % ('keepalive readline', m.hexdigest())
+
+def comp(N, url):
+    print '  making %i connections to:\n  %s' % (N, url)
+
+    sys.stdout.write('  first using the normal urllib handlers')
+    # first use normal opener
+    opener = urllib2.build_opener()
+    urllib2.install_opener(opener)
+    t1 = fetch(N, url)
+    print '  TIME: %.3f s' % t1
+
+    sys.stdout.write('  now using the keepalive handler       ')
+    # now install the keepalive handler and try again
+    opener = urllib2.build_opener(HTTPHandler())
+    urllib2.install_opener(opener)
+    t2 = fetch(N, url)
+    print '  TIME: %.3f s' % t2
+    print '  improvement factor: %.2f' % (t1/t2, )
+    
+def fetch(N, url, delay=0):
+    import time
+    lens = []
+    starttime = time.time()
+    for i in range(N):
+        if delay and i > 0: time.sleep(delay)
+        fo = urllib2.urlopen(url)
+        foo = fo.read()
+        fo.close()
+        lens.append(len(foo))
+    diff = time.time() - starttime
+
+    j = 0
+    for i in lens[1:]:
+        j = j + 1
+        if not i == lens[0]:
+            print "WARNING: inconsistent length on read %i: %i" % (j, i)
+
+    return diff
+
+def test_timeout(url):
+    global DEBUG
+    dbbackup = DEBUG
+    class FakeLogger:
+        def debug(self, msg, *args): print msg % args
+        info = warning = error = debug
+    DEBUG = FakeLogger()
+    print "  fetching the file to establish a connection"
+    fo = urllib2.urlopen(url)
+    data1 = fo.read()
+    fo.close()
+ 
+    i = 20
+    print "  waiting %i seconds for the server to close the connection" % i
+    while i > 0:
+        sys.stdout.write('\r  %2i' % i)
+        sys.stdout.flush()
+        time.sleep(1)
+        i -= 1
+    sys.stderr.write('\r')
+
+    print "  fetching the file a second time"
+    fo = urllib2.urlopen(url)
+    data2 = fo.read()
+    fo.close()
+
+    if data1 == data2:
+        print '  data are identical'
+    else:
+        print '  ERROR: DATA DIFFER'
+
+    DEBUG = dbbackup
+
+    
+def test(url, N=10):
+    print "checking error hander (do this on a non-200)"
+    try: error_handler(url)
+    except IOError, e:
+        print "exiting - exception will prevent further tests"
+        sys.exit()
+    print
+    print "performing continuity test (making sure stuff isn't corrupted)"
+    continuity(url)
+    print
+    print "performing speed comparison"
+    comp(N, url)
+    print
+    print "performing dropped-connection check"
+    test_timeout(url)
+    
+if __name__ == '__main__':
+    import time
+    import sys
+    try:
+        N = int(sys.argv[1])
+        url = sys.argv[2]
+    except:
+        print "%s <integer> <url>" % sys.argv[0]
+    else:
+        test(url, N)

mercurial/httprepo.py

@@ -1,226 +1,238
 # httprepo.py - HTTP repository proxy classes for mercurial
 #
 # Copyright 2005 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms
 # of the GNU General Public License, incorporated herein by reference.
 
 from node import *
 from remoterepo import *
 from i18n import gettext as _
 from demandload import *
 demandload(globals(), "hg os urllib urllib2 urlparse zlib util httplib")
+demandload(globals(), "keepalive")
 
 class passwordmgr(urllib2.HTTPPasswordMgr):
     def __init__(self, ui):
         urllib2.HTTPPasswordMgr.__init__(self)
         self.ui = ui
 
     def find_user_password(self, realm, authuri):
         authinfo = urllib2.HTTPPasswordMgr.find_user_password(
             self, realm, authuri)
         if authinfo != (None, None):
             return authinfo
 
         if not ui.interactive:
             raise util.Abort(_('http authorization required'))
 
         self.ui.write(_("http authorization required\n"))
         self.ui.status(_("realm: %s\n") % realm)
         user = self.ui.prompt(_("user:"), default=None)
         passwd = self.ui.getpass()
 
         self.add_password(realm, authuri, user, passwd)
         return (user, passwd)
 
 def netlocsplit(netloc):
     '''split [user[:passwd]@]host[:port] into 4-tuple.'''
 
     a = netloc.find('@')
     if a == -1:
         user, passwd = None, None
     else:
         userpass, netloc = netloc[:a], netloc[a+1:]
         c = userpass.find(':')
         if c == -1:
             user, passwd = urllib.unquote(userpass), None
         else:
             user = urllib.unquote(userpass[:c])
             passwd = urllib.unquote(userpass[c+1:])
     c = netloc.find(':')
     if c == -1:
         host, port = netloc, None
     else:
         host, port = netloc[:c], netloc[c+1:]
     return host, port, user, passwd
 
 def netlocunsplit(host, port, user=None, passwd=None):
     '''turn host, port, user, passwd into [user[:passwd]@]host[:port].'''
     if port:
         hostport = host + ':' + port
     else:
         hostport = host
     if user:
         if passwd:
             userpass = urllib.quote(user) + ':' + urllib.quote(passwd)
         else:
             userpass = urllib.quote(user)
         return userpass + '@' + hostport
     return hostport
 
 class httprepository(remoterepository):
     def __init__(self, ui, path):
         scheme, netloc, urlpath, query, frag = urlparse.urlsplit(path)
         if query or frag:
             raise util.Abort(_('unsupported URL component: "%s"') %
                              (query or frag))
         if not urlpath: urlpath = '/'
         host, port, user, passwd = netlocsplit(netloc)
 
         # urllib cannot handle URLs with embedded user or passwd
         self.url = urlparse.urlunsplit((scheme, netlocunsplit(host, port),
                                         urlpath, '', ''))
         self.ui = ui
 
         proxyurl = ui.config("http_proxy", "host") or os.getenv('http_proxy')
         proxyauthinfo = None
-        handler = urllib2.BaseHandler()
+        handler = keepalive.HTTPHandler()
 
         if proxyurl:
             # proxy can be proper url or host[:port]
             if not (proxyurl.startswith('http:') or
                     proxyurl.startswith('https:')):
                 proxyurl = 'http://' + proxyurl + '/'
             snpqf = urlparse.urlsplit(proxyurl)
             proxyscheme, proxynetloc, proxypath, proxyquery, proxyfrag = snpqf
             hpup = netlocsplit(proxynetloc)
 
             proxyhost, proxyport, proxyuser, proxypasswd = hpup
             if not proxyuser:
                 proxyuser = ui.config("http_proxy", "user")
                 proxypasswd = ui.config("http_proxy", "passwd")
 
             # see if we should use a proxy for this url
             no_list = [ "localhost", "127.0.0.1" ]
             no_list.extend([p.strip().lower() for
                             p in ui.config("http_proxy", "no", '').split(',')
                             if p.strip()])
             no_list.extend([p.strip().lower() for
                             p in os.getenv("no_proxy", '').split(',')
                             if p.strip()])
             # "http_proxy.always" config is for running tests on localhost
             if (not ui.configbool("http_proxy", "always") and
                 host.lower() in no_list):
                 ui.debug(_('disabling proxy for %s\n') % host)
             else:
                 proxyurl = urlparse.urlunsplit((
                     proxyscheme, netlocunsplit(proxyhost, proxyport,
                                                proxyuser, proxypasswd or ''),
                     proxypath, proxyquery, proxyfrag))
                 handler = urllib2.ProxyHandler({scheme: proxyurl})
                 ui.debug(_('proxying through %s\n') % proxyurl)
 
         # urllib2 takes proxy values from the environment and those
         # will take precedence if found, so drop them
         for env in ["HTTP_PROXY", "http_proxy", "no_proxy"]:
             try:
                 if os.environ.has_key(env):
                     del os.environ[env]
             except OSError:
                 pass
 
         passmgr = passwordmgr(ui)
         if user:
             ui.debug(_('will use user %s for http auth\n') % user)
             passmgr.add_password(None, host, user, passwd or '')
 
         opener = urllib2.build_opener(
             handler,
             urllib2.HTTPBasicAuthHandler(passmgr),
             urllib2.HTTPDigestAuthHandler(passmgr))
 
         # 1.0 here is the _protocol_ version
         opener.addheaders = [('User-agent', 'mercurial/proto-1.0')]
         urllib2.install_opener(opener)
 
     def dev(self):
         return -1
 
     def lock(self):
         raise util.Abort(_('operation not supported over http'))
 
     def do_cmd(self, cmd, **args):
         self.ui.debug(_("sending %s command\n") % cmd)
         q = {"cmd": cmd}
         q.update(args)
         qs = urllib.urlencode(q)
         cu = "%s?%s" % (self.url, qs)
         try:
             resp = urllib2.urlopen(cu)
         except httplib.HTTPException, inst:
             self.ui.debug(_('http error while sending %s command\n') % cmd)
             self.ui.print_exc()
             raise IOError(None, inst)
+        try:
+            proto = resp.getheader('content-type')
+        except AttributeError:
         proto = resp.headers['content-type']
 
         # accept old "text/plain" and "application/hg-changegroup" for now
         if not proto.startswith('application/mercurial') and \
                not proto.startswith('text/plain') and \
                not proto.startswith('application/hg-changegroup'):
             raise hg.RepoError(_("'%s' does not appear to be an hg repository") %
                                self.url)
 
         if proto.startswith('application/mercurial'):
             version = proto[22:]
             if float(version) > 0.1:
                 raise hg.RepoError(_("'%s' uses newer protocol %s") %
                                    (self.url, version))
 
         return resp
 
+    def do_read(self, cmd, **args):
+        fp = self.do_cmd(cmd, **args)
+        try:
+            return fp.read()
+        finally:
+            # if using keepalive, allow connection to be reused
+            fp.close()
+
     def heads(self):
-        d = self.do_cmd("heads").read()
+        d = self.do_read("heads")
         try:
             return map(bin, d[:-1].split(" "))
         except:
             self.ui.warn(_("unexpected response:\n") + d[:400] + "\n...\n")
             raise
 
     def branches(self, nodes):
         n = " ".join(map(hex, nodes))
-        d = self.do_cmd("branches", nodes=n).read()
+        d = self.do_read("branches", nodes=n)
         try:
             br = [ tuple(map(bin, b.split(" "))) for b in d.splitlines() ]
             return br
         except:
             self.ui.warn(_("unexpected response:\n") + d[:400] + "\n...\n")
             raise
 
     def between(self, pairs):
         n = "\n".join(["-".join(map(hex, p)) for p in pairs])
-        d = self.do_cmd("between", pairs=n).read()
+        d = self.do_read("between", pairs=n)
         try:
             p = [ l and map(bin, l.split(" ")) or [] for l in d.splitlines() ]
             return p
         except:
             self.ui.warn(_("unexpected response:\n") + d[:400] + "\n...\n")
             raise
 
     def changegroup(self, nodes, kind):
         n = " ".join(map(hex, nodes))
         f = self.do_cmd("changegroup", roots=n)
         bytes = 0
 
         def zgenerator(f):
             zd = zlib.decompressobj()
             try:
                 for chnk in f:
                     yield zd.decompress(chnk)
             except httplib.HTTPException, inst:
                 raise IOError(None, _('connection ended unexpectedly'))
             yield zd.flush()
 
         return util.chunkbuffer(zgenerator(util.filechunkiter(f)))
 
 class httpsrepository(httprepository):
     pass