#   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