Source

CherryPy / cherrypy / wsgiserver.py

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"""A high-speed, production ready, thread pooled, generic WSGI server.

Simplest example on how to use this module directly
(without using CherryPy's application machinery):

    from cherrypy import wsgiserver
    
    def my_crazy_app(environ, start_response):
        status = '200 OK'
        response_headers = [('Content-type','text/plain')]
        start_response(status, response_headers)
        return ['Hello world!\n']
    
    # Here we set our application to the script_name '/' 
    wsgi_apps = [('/', my_crazy_app)]
    
    server = wsgiserver.CherryPyWSGIServer(('localhost', 8070), wsgi_apps,
                                           server_name='localhost')
    
    # Want SSL support? Just set these attributes
    # server.ssl_certificate = <filename>
    # server.ssl_private_key = <filename>
    
    if __name__ == '__main__':
        server.start()

This won't call the CherryPy engine (application side) at all, only the
WSGI server, which is independant from the rest of CherryPy. Don't
let the name "CherryPyWSGIServer" throw you; the name merely reflects
its origin, not it's coupling.

The CherryPy WSGI server can serve as many WSGI application
as you want in one instance:

    wsgi_apps = [('/', my_crazy_app), (/blog', my_blog_app)]

"""


import base64
import Queue
import os
import re
quoted_slash = re.compile("(?i)%2F")
import rfc822
import socket
try:
    import cStringIO as StringIO
except ImportError:
    import StringIO
import sys
import threading
import time
import traceback
from urllib import unquote
from urlparse import urlparse

try:
    from OpenSSL import SSL
    from OpenSSL import crypto
except ImportError:
    SSL = None

import errno
socket_errors_to_ignore = []
# Not all of these names will be defined for every platform.
for _ in ("EPIPE", "ETIMEDOUT", "ECONNREFUSED", "ECONNRESET",
          "EHOSTDOWN", "EHOSTUNREACH",
          "WSAECONNABORTED", "WSAECONNREFUSED", "WSAECONNRESET",
          "WSAENETRESET", "WSAETIMEDOUT"):
    if _ in dir(errno):
        socket_errors_to_ignore.append(getattr(errno, _))
# de-dupe the list
socket_errors_to_ignore = dict.fromkeys(socket_errors_to_ignore).keys()
socket_errors_to_ignore.append("timed out")

comma_separated_headers = ['ACCEPT', 'ACCEPT-CHARSET', 'ACCEPT-ENCODING',
    'ACCEPT-LANGUAGE', 'ACCEPT-RANGES', 'ALLOW', 'CACHE-CONTROL',
    'CONNECTION', 'CONTENT-ENCODING', 'CONTENT-LANGUAGE', 'EXPECT',
    'IF-MATCH', 'IF-NONE-MATCH', 'PRAGMA', 'PROXY-AUTHENTICATE', 'TE',
    'TRAILER', 'TRANSFER-ENCODING', 'UPGRADE', 'VARY', 'VIA', 'WARNING',
    'WWW-AUTHENTICATE']

class HTTPRequest(object):
    """An HTTP Request (and response).
    
    A single HTTP connection may consist of multiple request/response pairs.
    
    connection: the HTTP Connection object which spawned this request.
    rfile: the 'read' fileobject from the connection's socket
    ready: when True, the request has been parsed and is ready to begin
        generating the response. When False, signals the calling Connection
        that the response should not be generated and the connection should
        close.
    close_connection: signals the calling Connection that the request
        should close. This does not imply an error! The client and/or
        server may each request that the connection be closed.
    chunked_write: if True, output will be encoded with the "chunked"
        transfer-coding. This value is set automatically inside
        send_headers.
    """
    
    def __init__(self, connection):
        self.connection = connection
        self.rfile = self.connection.rfile
        self.sendall = self.connection.sendall
        self.environ = connection.environ.copy()
        
        self.ready = False
        self.started_response = False
        self.status = ""
        self.outheaders = []
        self.sent_headers = False
        self.close_connection = False
        self.chunked_write = False
    
    def parse_request(self):
        """Parse the next HTTP request start-line and message-headers."""
        # HTTP/1.1 connections are persistent by default. If a client
        # requests a page, then idles (leaves the connection open),
        # then rfile.readline() will raise socket.error("timed out").
        # Note that it does this based on the value given to settimeout(),
        # and doesn't need the client to request or acknowledge the close
        # (although your TCP stack might suffer for it: cf Apache's history
        # with FIN_WAIT_2).
        request_line = self.rfile.readline()
        if not request_line:
            # Force self.ready = False so the connection will close.
            self.ready = False
            return
        
        if request_line == "\r\n":
            # RFC 2616 sec 4.1: "...if the server is reading the protocol
            # stream at the beginning of a message and receives a CRLF
            # first, it should ignore the CRLF."
            # But only ignore one leading line! else we enable a DoS.
            request_line = self.rfile.readline()
            if not request_line:
                self.ready = False
                return
        
        server = self.connection.server
        self.environ["SERVER_SOFTWARE"] = "%s WSGI Server" % server.version
        
        method, path, req_protocol = request_line.strip().split(" ", 2)
        self.environ["REQUEST_METHOD"] = method
        
        # path may be an abs_path (including "http://host.domain.tld");
        scheme, location, path, params, qs, frag = urlparse(path)
        
        if frag:
            self.simple_response("400 Bad Request",
                                 "Illegal #fragment in Request-URI.")
            return
        
        if scheme:
            self.environ["wsgi.url_scheme"] = scheme
        if params:
            path = path + ";" + params
        
        # Unquote the path+params (e.g. "/this%20path" -> "this path").
        # http://www.w3.org/Protocols/rfc2616/rfc2616-sec5.html#sec5.1.2
        #
        # But note that "...a URI must be separated into its components
        # before the escaped characters within those components can be
        # safely decoded." http://www.ietf.org/rfc/rfc2396.txt, sec 2.4.2
        atoms = [unquote(x) for x in quoted_slash.split(path)]
        path = "%2F".join(atoms)
        
        if path == "*":
            # This means, of course, that the last wsgi_app (shortest path)
            # will always handle a URI of "*".
            self.environ["SCRIPT_NAME"] = ""
            self.environ["PATH_INFO"] = "*"
            self.wsgi_app = server.mount_points[-1][1]
        else:
            for mount_point, wsgi_app in server.mount_points:
                # The mount_points list should be sorted by length, descending.
                if path.startswith(mount_point + "/") or path == mount_point:
                    self.environ["SCRIPT_NAME"] = mount_point
                    self.environ["PATH_INFO"] = path[len(mount_point):]
                    self.wsgi_app = wsgi_app
                    break
            else:
                self.simple_response("404 Not Found")
                return
        
        # Note that, like wsgiref and most other WSGI servers,
        # we unquote the path but not the query string.
        self.environ["QUERY_STRING"] = qs
        
        # Compare request and server HTTP protocol versions, in case our
        # server does not support the requested protocol. Limit our output
        # to min(req, server). We want the following output:
        #     request    server     actual written   supported response
        #     protocol   protocol  response protocol    feature set
        # a     1.0        1.0           1.0                1.0
        # b     1.0        1.1           1.1                1.0
        # c     1.1        1.0           1.0                1.0
        # d     1.1        1.1           1.1                1.1
        # Notice that, in (b), the response will be "HTTP/1.1" even though
        # the client only understands 1.0. RFC 2616 10.5.6 says we should
        # only return 505 if the _major_ version is different.
        rp = int(req_protocol[5]), int(req_protocol[7])
        sp = int(server.protocol[5]), int(server.protocol[7])
        if sp[0] != rp[0]:
            self.simple_response("505 HTTP Version Not Supported")
            return
        # Bah. "SERVER_PROTOCOL" is actually the REQUEST protocol.
        self.environ["SERVER_PROTOCOL"] = req_protocol
        # set a non-standard environ entry so the WSGI app can know what
        # the *real* server protocol is (and what features to support).
        # See http://www.faqs.org/rfcs/rfc2145.html.
        self.environ["ACTUAL_SERVER_PROTOCOL"] = server.protocol
        self.response_protocol = "HTTP/%s.%s" % min(rp, sp)
        
        # If the Request-URI was an absoluteURI, use its location atom.
        if location:
            self.environ["SERVER_NAME"] = location
        
        # then all the http headers
        headers = rfc822.Message(self.rfile, seekable=0)
        self.environ.update(self.parse_headers(headers))
        
        creds = headers.getheader("Authorization", "").split(" ", 1)
        self.environ["AUTH_TYPE"] = creds[0]
        if creds[0].lower() == 'basic':
            user, pw = base64.decodestring(creds[1]).split(":", 1)
            self.environ["REMOTE_USER"] = user
        
        # Persistent connection support
        if self.response_protocol == "HTTP/1.1":
            if headers.getheader("Connection", "") == "close":
                self.close_connection = True
                self.outheaders.append(("Connection", "close"))
        else:
            # HTTP/1.0
            if headers.getheader("Connection", "") == "Keep-Alive":
                if self.close_connection == False:
                    self.outheaders.append(("Connection", "Keep-Alive"))
            else:
                self.close_connection = True
        
        # Transfer-Encoding support
        te = headers.getheader("Transfer-Encoding", "")
        te = [x.strip() for x in te.split(",") if x.strip()]
        if te:
            while te:
                enc = te.pop()
                if enc.lower() == "chunked":
                    if not self.decode_chunked():
                        return
                else:
                    self.simple_response("501 Unimplemented")
                    self.close_connection = True
                    return
        else:
            cl = headers.getheader("Content-length")
            if method in ("POST", "PUT") and cl is None:
                # No Content-Length header supplied. This will hang
                # cgi.FieldStorage, since it cannot determine when to
                # stop reading from the socket.
                # See http://www.cherrypy.org/ticket/493.
                self.simple_response("411 Length Required")
                return
        
        # From PEP 333:
        # "Servers and gateways that implement HTTP 1.1 must provide
        # transparent support for HTTP 1.1's "expect/continue" mechanism.
        # This may be done in any of several ways:
        #   1. Respond to requests containing an Expect: 100-continue request
        #      with an immediate "100 Continue" response, and proceed normally.
        #   2. Proceed with the request normally, but provide the application
        #      with a wsgi.input stream that will send the "100 Continue"
        #      response if/when the application first attempts to read from
        #      the input stream. The read request must then remain blocked
        #      until the client responds.
        #   3. Wait until the client decides that the server does not support
        #      expect/continue, and sends the request body on its own.
        #      (This is suboptimal, and is not recommended.)
        #
        # We used to do 3, but are now doing 1. Maybe we'll do 2 someday,
        # but it seems like it would be a big slowdown for such a rare case.
        if headers.getheader("Expect", "") == "100-continue":
            self.simple_response(100)
        
        self.ready = True
    
    def parse_headers(self, headers):
        """Parse the given HTTP request message-headers."""
        environ = {}
        ct = headers.dict.get("content-type")
        if ct:
            environ["CONTENT_TYPE"] = ct
        cl = headers.dict.get("content-length")
        if cl:
            environ["CONTENT_LENGTH"] = cl
        
        for line in headers.headers:
            if line[:1].isspace():
                v = line.strip()
            else:
                k, v = line.split(":", 1)
                k, v = k.strip().upper(), v.strip()
                envname = "HTTP_" + k.replace("-", "_")
            
            if k in comma_separated_headers:
                existing = environ.get(envname)
                if existing:
                    v = ", ".join((existing, v))
            environ[envname] = v
        
        return environ
    
    def decode_chunked(self):
        """Decode the 'chunked' transfer coding."""
        cl = 0
        data = StringIO.StringIO()
        while True:
            line = self.rfile.readline().strip().split(";", 1)
            chunk_size = int(line.pop(0), 16)
            if chunk_size <= 0:
                break
##            if line: chunk_extension = line[0]
            cl += chunk_size
            data.write(self.rfile.read(chunk_size))
            crlf = self.rfile.read(2)
            if crlf != "\r\n":
                self.simple_response("400 Bad Request",
                                     "Bad chunked transfer coding "
                                     "(expected '\\r\\n', got %r)" % crlf)
                return
        
        # Grab any trailer headers
        headers = rfc822.Message(self.rfile, seekable=0)
        self.environ.update(self.parse_headers(headers))
        
        data.seek(0)
        self.environ["wsgi.input"] = data
        self.environ["CONTENT_LENGTH"] = str(cl) or ""
        return True
    
    def respond(self):
        """Call the appropriate WSGI app and write its iterable output."""
        response = self.wsgi_app(self.environ, self.start_response)
        try:
            for chunk in response:
                self.write(chunk)
        finally:
            if hasattr(response, "close"):
                response.close()
        if (self.ready and not self.sent_headers
                and not self.connection.server.interrupt):
            self.sent_headers = True
            self.send_headers()
        if self.chunked_write:
            self.sendall("0\r\n\r\n")
    
    def simple_response(self, status, msg=""):
        """Write a simple response back to the client."""
        status = str(status)
        buf = ["%s %s\r\n" % (self.connection.server.protocol, status),
               "Content-Length: %s\r\n" % len(msg)]
        
        if status[:3] == "413" and self.response_protocol == 'HTTP/1.1':
            # Request Entity Too Large
            self.close_connection = True
            buf.append("Connection: close\r\n")
        
        buf.append("\r\n")
        if msg:
            buf.append(msg)
        self.sendall("".join(buf))
    
    def start_response(self, status, headers, exc_info = None):
        """WSGI callable to begin the HTTP response."""
        if self.started_response:
            if not exc_info:
                assert False, "Already started response"
            else:
                try:
                    raise exc_info[0], exc_info[1], exc_info[2]
                finally:
                    exc_info = None
        self.started_response = True
        self.status = status
        self.outheaders.extend(headers)
        return self.write
    
    def write(self, chunk):
        """WSGI callable to write unbuffered data to the client.
        
        This method is also used internally by start_response (to write
        data from the iterable returned by the WSGI application).
        """
        if not self.sent_headers:
            self.sent_headers = True
            self.send_headers()
        if self.chunked_write:
            buf = [hex(len(chunk))[2:],
                   "\r\n", chunk, "\r\n"]
            self.sendall("".join(buf))
        else:
            self.sendall(chunk)
    
    def send_headers(self):
        """Assert, process, and send the HTTP response message-headers."""
        hkeys = [key.lower() for (key, value) in self.outheaders]
        status = int(self.status[:3])
        
        if self.response_protocol == 'HTTP/1.1':
            if status == 413:
                # Request Entity Too Large. Close conn to avoid garbage.
                self.close_connection = True
            elif "content-length" not in hkeys:
                # "All 1xx (informational), 204 (no content),
                # and 304 (not modified) responses MUST NOT
                # include a message-body." So no point chunking.
                if status < 200 or status in (204, 205, 304):
                    pass
                else:
                    # Use the chunked transfer-coding
                    self.chunked_write = True
                    self.outheaders.append(("Transfer-Encoding", "chunked"))
        
        if self.close_connection and "connection" not in hkeys:
            self.outheaders.append(("Connection", "close"))
        
        if "date" not in hkeys:
            self.outheaders.append(("Date", rfc822.formatdate()))
        
        server = self.connection.server
        
        if "server" not in hkeys:
            self.outheaders.append(("Server", server.version))
        
        buf = [server.protocol, " ", self.status, "\r\n"]
        try:
            for k, v in self.outheaders:
                buf.append(k + ": " + v + "\r\n")
        except TypeError:
            if not isinstance(k, str):
                raise TypeError("WSGI response header key %r is not a string.")
            if not isinstance(v, str):
                raise TypeError("WSGI response header value %r is not a string.")
            else:
                raise
        buf.append("\r\n")
        self.sendall("".join(buf))


def _ssl_wrap_method(method, is_reader=False):
    """Wrap the given method with SSL error-trapping.
    
    is_reader: if False (the default), EOF errors will be raised.
        If True, EOF errors will return "" (to emulate normal sockets).
    """
    def ssl_method_wrapper(self, *args, **kwargs):
##        print (id(self), method, args, kwargs)
        start = time.time()
        while True:
            try:
                return method(self, *args, **kwargs)
            except (SSL.WantReadError, SSL.WantWriteError):
                # Sleep and try again. This is dangerous, because it means
                # the rest of the stack has no way of differentiating
                # between a "new handshake" error and "client dropped".
                # Note this isn't an endless loop: there's a timeout below.
                time.sleep(self.ssl_retry)
            except SSL.SysCallError, e:
                if is_reader and e.args == (-1, 'Unexpected EOF'):
                    return ""
                
                errno = e.args[0]
                if is_reader and errno in socket_errors_to_ignore:
                    return ""
                raise socket.error(errno)
            except SSL.Error, e:
                if is_reader and e.args == (-1, 'Unexpected EOF'):
                    return ""
                if is_reader and e.args[0][0][2] == 'ssl handshake failure':
                    return ""
                raise
            if time.time() - start > self.ssl_timeout:
                raise socket.timeout("timed out")
    return ssl_method_wrapper

class SSL_fileobject(socket._fileobject):
    """Faux file object attached to a socket object."""
    
    ssl_timeout = 3
    ssl_retry = .01
    
    close = _ssl_wrap_method(socket._fileobject.close)
    flush = _ssl_wrap_method(socket._fileobject.flush)
    write = _ssl_wrap_method(socket._fileobject.write)
    writelines = _ssl_wrap_method(socket._fileobject.writelines)
    read = _ssl_wrap_method(socket._fileobject.read, is_reader=True)
    readline = _ssl_wrap_method(socket._fileobject.readline, is_reader=True)
    readlines = _ssl_wrap_method(socket._fileobject.readlines, is_reader=True)


class HTTPConnection(object):
    """An HTTP connection (active socket).
    
    socket: the raw socket object (usually TCP) for this connection.
    addr: the "bind address" for the remote end of the socket.
        For IP sockets, this is a tuple of (REMOTE_ADDR, REMOTE_PORT).
        For UNIX domain sockets, this will be a string.
    server: the HTTP Server for this Connection. Usually, the server
        object possesses a passive (server) socket which spawns multiple,
        active (client) sockets, one for each connection.
    
    environ: a WSGI environ template. This will be copied for each request.
    rfile: a fileobject for reading from the socket.
    sendall: a function for writing (+ flush) to the socket.
    """
    
    rbufsize = -1
    RequestHandlerClass = HTTPRequest
    environ = {"wsgi.version": (1, 0),
               "wsgi.url_scheme": "http",
               "wsgi.multithread": True,
               "wsgi.multiprocess": False,
               "wsgi.run_once": False,
               "wsgi.errors": sys.stderr,
               }
    
    def __init__(self, sock, addr, server):
        self.socket = sock
        self.addr = addr
        self.server = server
        
        # Copy the class environ into self.
        self.environ = self.environ.copy()
        
        if SSL and isinstance(sock, SSL.ConnectionType):
            timeout = sock.gettimeout()
            self.rfile = SSL_fileobject(sock, "r", self.rbufsize)
            self.rfile.ssl_timeout = timeout
            self.sendall = _ssl_wrap_method(sock.sendall)
            self.environ["wsgi.url_scheme"] = "https"
            self.environ["HTTPS"] = "on"
            sslenv = getattr(server, "ssl_environ", None)
            if sslenv:
                self.environ.update(sslenv)
        else:
            self.rfile = sock.makefile("r", self.rbufsize)
            self.sendall = sock.sendall
        
        self.environ.update({"wsgi.input": self.rfile,
                             "SERVER_NAME": self.server.server_name,
                             })
        
        if isinstance(self.server.bind_addr, basestring):
            # AF_UNIX. This isn't really allowed by WSGI, which doesn't
            # address unix domain sockets. But it's better than nothing.
            self.environ["SERVER_PORT"] = ""
        else:
            self.environ["SERVER_PORT"] = str(self.server.bind_addr[1])
            # optional values
            # Until we do DNS lookups, omit REMOTE_HOST
            self.environ["REMOTE_ADDR"] = self.addr[0]
            self.environ["REMOTE_PORT"] = str(self.addr[1])
    
    def communicate(self):
        """Read each request and respond appropriately."""
        try:
            while True:
                # (re)set req to None so that if something goes wrong in
                # the RequestHandlerClass constructor, the error doesn't
                # get written to the previous request.
                req = None
                req = self.RequestHandlerClass(self)
                # This order of operations should guarantee correct pipelining.
                req.parse_request()
                if not req.ready:
                    return
                req.respond()
                if req.close_connection:
                    return
        except socket.error, e:
            errno = e.args[0]
            if errno not in socket_errors_to_ignore:
                if req:
                    req.simple_response("500 Internal Server Error",
                                        format_exc())
            return
        except (KeyboardInterrupt, SystemExit):
            raise
        except:
            if req:
                req.simple_response("500 Internal Server Error", format_exc())
    
    def close(self):
        """Close the socket underlying this connection."""
        self.rfile.close()
        self.socket.close()


def format_exc(limit=None):
    """Like print_exc() but return a string. Backport for Python 2.3."""
    try:
        etype, value, tb = sys.exc_info()
        return ''.join(traceback.format_exception(etype, value, tb, limit))
    finally:
        etype = value = tb = None


_SHUTDOWNREQUEST = None

class WorkerThread(threading.Thread):
    """Thread which continuously polls a Queue for Connection objects.
    
    server: the HTTP Server which spawned this thread, and which owns the
        Queue and is placing active connections into it.
    ready: a simple flag for the calling server to know when this thread
        has begun polling the Queue.
    
    Due to the timing issues of polling a Queue, a WorkerThread does not
    check its own 'ready' flag after it has started. To stop the thread,
    it is necessary to stick a _SHUTDOWNREQUEST object onto the Queue
    (one for each running WorkerThread).
    """
    
    def __init__(self, server):
        self.ready = False
        self.server = server
        threading.Thread.__init__(self)
    
    def run(self):
        try:
            self.ready = True
            while True:
                conn = self.server.requests.get()
                if conn is _SHUTDOWNREQUEST:
                    return
                
                try:
                    conn.communicate()
                finally:
                    conn.close()
        except (KeyboardInterrupt, SystemExit), exc:
            self.server.interrupt = exc


class SSLConnection:
    """A thread-safe wrapper for an SSL.Connection.
    
    *args: the arguments to create the wrapped SSL.Connection(*args).
    """
    
    def __init__(self, *args):
        self._ssl_conn = SSL.Connection(*args)
        self._lock = threading.RLock()
    
    for f in ('get_context', 'pending', 'send', 'write', 'recv', 'read',
              'renegotiate', 'bind', 'listen', 'connect', 'accept',
              'setblocking', 'fileno', 'shutdown', 'close', 'get_cipher_list',
              'getpeername', 'getsockname', 'getsockopt', 'setsockopt',
              'makefile', 'get_app_data', 'set_app_data', 'state_string',
              'sock_shutdown', 'get_peer_certificate', 'want_read',
              'want_write', 'set_connect_state', 'set_accept_state',
              'connect_ex', 'sendall', 'settimeout'):
        exec """def %s(self, *args):
        self._lock.acquire()
        try:
            return self._ssl_conn.%s(*args)
        finally:
            self._lock.release()
""" % (f, f)


class CherryPyWSGIServer(object):
    """An HTTP server for WSGI.
    
    bind_addr: a (host, port) tuple if TCP sockets are desired;
        for UNIX sockets, supply the filename as a string.
    wsgi_app: the WSGI 'application callable'; multiple WSGI applications
        may be passed as (script_name, callable) pairs.
    numthreads: the number of worker threads to create (default 10).
    server_name: the string to set for WSGI's SERVER_NAME environ entry.
        Defaults to socket.gethostname().
    max: the maximum number of queued requests (defaults to -1 = no limit).
    request_queue_size: the 'backlog' argument to socket.listen();
        specifies the maximum number of queued connections (default 5).
    timeout: the timeout in seconds for accepted connections (default 10).
    
    protocol: the version string to write in the Status-Line of all
        HTTP responses. For example, "HTTP/1.1" (the default). This
        also limits the supported features used in the response.
    
    
    SSL/HTTPS
    ---------
    The OpenSSL module must be importable for SSL functionality.
    You can obtain it from http://pyopenssl.sourceforge.net/
    
    ssl_certificate: the filename of the server SSL certificate.
    ssl_privatekey: the filename of the server's private key file.
    
    If either of these is None (both are None by default), this server
    will not use SSL. If both are given and are valid, they will be read
    on server start and used in the SSL context for the listening socket.
    """
    
    protocol = "HTTP/1.1"
    version = "CherryPy/3.0.0"
    ready = False
    _interrupt = None
    ConnectionClass = HTTPConnection
    
    # Paths to certificate and private key files
    ssl_certificate = None
    ssl_private_key = None
    
    def __init__(self, bind_addr, wsgi_app, numthreads=10, server_name=None,
                 max=-1, request_queue_size=5, timeout=10):
        self.requests = Queue.Queue(max)
        
        if callable(wsgi_app):
            # We've been handed a single wsgi_app, in CP-2.1 style.
            # Assume it's mounted at "".
            self.mount_points = [("", wsgi_app)]
        else:
            # We've been handed a list of (mount_point, wsgi_app) tuples,
            # so that the server can call different wsgi_apps, and also
            # correctly set SCRIPT_NAME.
            self.mount_points = wsgi_app
        self.mount_points.sort()
        self.mount_points.reverse()
        
        self.bind_addr = bind_addr
        self.numthreads = numthreads or 1
        if not server_name:
            server_name = socket.gethostname()
        self.server_name = server_name
        self.request_queue_size = request_queue_size
        self._workerThreads = []
        
        self.timeout = timeout
    
    def start(self):
        """Run the server forever."""
        # We don't have to trap KeyboardInterrupt or SystemExit here,
        # because cherrpy.server already does so, calling self.stop() for us.
        # If you're using this server with another framework, you should
        # trap those exceptions in whatever code block calls start().
        self._interrupt = None
        
        def bind(family, type, proto=0):
            """Create (or recreate) the actual socket object."""
            self.socket = socket.socket(family, type, proto)
            self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
            if self.ssl_certificate and self.ssl_private_key:
                if SSL is None:
                    raise ImportError("You must install pyOpenSSL to use HTTPS.")
                
                # See http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/442473
                ctx = SSL.Context(SSL.SSLv23_METHOD)
                ctx.use_privatekey_file(self.ssl_private_key)
                ctx.use_certificate_file(self.ssl_certificate)
                self.socket = SSLConnection(ctx, self.socket)
                self.populate_ssl_environ()
            self.socket.bind(self.bind_addr)
        
        # Select the appropriate socket
        if isinstance(self.bind_addr, basestring):
            # AF_UNIX socket
            
            # So we can reuse the socket...
            try: os.unlink(self.bind_addr)
            except: pass
            
            # So everyone can access the socket...
            try: os.chmod(self.bind_addr, 0777)
            except: pass
            
            info = [(socket.AF_UNIX, socket.SOCK_STREAM, 0, "", self.bind_addr)]
        else:
            # AF_INET or AF_INET6 socket
            # Get the correct address family for our host (allows IPv6 addresses)
            host, port = self.bind_addr
            flags = 0
            if host == '':
                # Despite the socket module docs, using '' does not
                # allow AI_PASSIVE to work. Passing None instead
                # returns '0.0.0.0' like we want. In other words:
                #     host    AI_PASSIVE     result
                #      ''         Y         192.168.x.y
                #      ''         N         192.168.x.y
                #     None        Y         0.0.0.0
                #     None        N         127.0.0.1
                host = None
                flags = socket.AI_PASSIVE
            try:
                info = socket.getaddrinfo(host, port, socket.AF_UNSPEC,
                                          socket.SOCK_STREAM, 0, flags)
            except socket.gaierror:
                # Probably a DNS issue. Assume IPv4.
                info = [(socket.AF_INET, socket.SOCK_STREAM, 0, "", self.bind_addr)]
        
        self.socket = None
        msg = "No socket could be created"
        for res in info:
            af, socktype, proto, canonname, sa = res
            try:
                bind(af, socktype, proto)
            except socket.error, msg:
                if self.socket:
                    self.socket.close()
                self.socket = None
                continue
            break
        if not self.socket:
            raise socket.error, msg
        
        # Timeout so KeyboardInterrupt can be caught on Win32
        self.socket.settimeout(1)
        self.socket.listen(self.request_queue_size)
        
        # Create worker threads
        for i in xrange(self.numthreads):
            self._workerThreads.append(WorkerThread(self))
        for worker in self._workerThreads:
            worker.setName("CP WSGIServer " + worker.getName())
            worker.start()
        for worker in self._workerThreads:
            while not worker.ready:
                time.sleep(.1)
        
        self.ready = True
        while self.ready:
            self.tick()
            if self.interrupt:
                while self.interrupt is True:
                    # Wait for self.stop() to complete. See _set_interrupt.
                    time.sleep(0.1)
                raise self.interrupt
    
    def tick(self):
        """Accept a new connection and put it on the Queue."""
        try:
            s, addr = self.socket.accept()
            if not self.ready:
                return
            if hasattr(s, 'settimeout'):
                s.settimeout(self.timeout)
            conn = self.ConnectionClass(s, addr, self)
            self.requests.put(conn)
        except socket.timeout:
            # The only reason for the timeout in start() is so we can
            # notice keyboard interrupts on Win32, which don't interrupt
            # accept() by default
            return
        except socket.error, x:
            msg = x.args[1]
            if msg in ("Bad file descriptor", "Socket operation on non-socket"):
                # Our socket was closed.
                return
            if msg == "Resource temporarily unavailable":
                # Just try again. See http://www.cherrypy.org/ticket/479.
                return
            raise
    
    def _get_interrupt(self):
        return self._interrupt
    def _set_interrupt(self, interrupt):
        self._interrupt = True
        self.stop()
        self._interrupt = interrupt
    interrupt = property(_get_interrupt, _set_interrupt,
                         doc="Set this to an Exception instance to "
                             "interrupt the server.")
    
    def stop(self):
        """Gracefully shutdown a server that is serving forever."""
        self.ready = False
        
        sock = getattr(self, "socket", None)
        if sock:
            if not isinstance(self.bind_addr, basestring):
                # Touch our own socket to make accept() return immediately.
                try:
                    host, port = sock.getsockname()[:2]
                except socket.error, x:
                    if x.args[1] != "Bad file descriptor":
                        raise
                else:
                    # Note that we're explicitly NOT using AI_PASSIVE,
                    # here, because we want an actual IP to touch.
                    # localhost won't work if we've bound to a public IP,
                    # but it would if we bound to INADDR_ANY via host = ''.
                    for res in socket.getaddrinfo(host, port, socket.AF_UNSPEC,
                                                  socket.SOCK_STREAM):
                        af, socktype, proto, canonname, sa = res
                        s = None
                        try:
                            s = socket.socket(af, socktype, proto)
                            # See http://groups.google.com/group/cherrypy-users/
                            #        browse_frm/thread/bbfe5eb39c904fe0
                            s.settimeout(1.0)
                            s.connect((host, port))
                            s.close()
                        except socket.error:
                            if s:
                                s.close()
            if hasattr(sock, "close"):
                sock.close()
            self.socket = None
        
        # Must shut down threads here so the code that calls
        # this method can know when all threads are stopped.
        for worker in self._workerThreads:
            self.requests.put(_SHUTDOWNREQUEST)
        
        # Don't join currentThread (when stop is called inside a request).
        current = threading.currentThread()
        while self._workerThreads:
            worker = self._workerThreads.pop()
            if worker is not current and worker.isAlive:
                try:
                    worker.join()
                except AssertionError:
                    pass
    
    def populate_ssl_environ(self):
        """Create WSGI environ entries to be merged into each request."""
        cert = open(self.ssl_certificate).read()
        cert = crypto.load_certificate(crypto.FILETYPE_PEM, cert)
        self.ssl_environ = {
            # pyOpenSSL doesn't provide access to any of these AFAICT
##            'SSL_PROTOCOL': 'SSLv2',
##            SSL_CIPHER 	string 	The cipher specification name
##            SSL_VERSION_INTERFACE 	string 	The mod_ssl program version
##            SSL_VERSION_LIBRARY 	string 	The OpenSSL program version
            }
        
        # Server certificate attributes
        self.ssl_environ.update({
            'SSL_SERVER_M_VERSION': cert.get_version(),
            'SSL_SERVER_M_SERIAL': cert.get_serial_number(),
##            'SSL_SERVER_V_START': Validity of server's certificate (start time),
##            'SSL_SERVER_V_END': Validity of server's certificate (end time),
            })
        
        for prefix, dn in [("I", cert.get_issuer()),
                           ("S", cert.get_subject())]:
            # X509Name objects don't seem to have a way to get the
            # complete DN string. Use str() and slice it instead,
            # because str(dn) == "<X509Name object '/C=US/ST=...'>"
            dnstr = str(dn)[18:-2]
            
            wsgikey = 'SSL_SERVER_%s_DN' % prefix
            self.ssl_environ[wsgikey] = dnstr
            
            # The DN should be of the form: /k1=v1/k2=v2, but we must allow
            # for any value to contain slashes itself (in a URL).
            while dnstr:
                pos = dnstr.rfind("=")
                dnstr, value = dnstr[:pos], dnstr[pos + 1:]
                pos = dnstr.rfind("/")
                dnstr, key = dnstr[:pos], dnstr[pos + 1:]
                if key and value:
                    wsgikey = 'SSL_SERVER_%s_DN_%s' % (prefix, key)
                    self.ssl_environ[wsgikey] = value
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