Asynchronous HTTP server (Python recipe) by Josiah Carlson

ActiveState Code (http://code.activestate.com/recipes/440665/)

"""
Get an updated version of this server from:
    http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/440665


Original pseudo-async* version by Pierre Quentel, available from
    http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/259148

* It would only be async while reading requests, it would switch to a
synchronous write to a socket when writing a response to a socket.  Ick.


Features this version offers:
1. Uses asynchronous reading and writing to/from sockets all the time.
2. Performs sectioned reads from on-disk files, allowing for serving files of
   unlimited size.
3. More informative logging.
4. A quick wrapper for logging to a file and stdout/stderr.
5. Trailing-slash redirects on directories.
6. Optional built-in favicon.ico (to reduce the number of spurious log
   entries).
7. Subclass which does not allow any directory lists or redirecting to
   /index.htm[l] .
8. Subclass which does not allow any directory lists, but does automatic
   redirection to /index.htm[l] .
9. Doesn't try to open reserved names on Windows.
10. Has a tuning mechanism to change buffer performance depending on small
    or large files.

For most people, one can run this from the command line and get a reasonably
functioning web server with minor issue.

I benchmarked this version in my personal projects folder, which contains
around a gig of files, sizes ranging from a few kilobytes, to 100 megabytes.
I then performed two concurrent "wget -m http://localhost/" calls (from
different paths) on Windows 2k (machine is a P4 2.8ghz with hyperthreading,
1.5 gigs memory, reading from an 80 gig SATA drive, writing to a 120 gig PATA
drive).

On small files, it was able to serve up 15-30 files/second. On larger (10+
meg) files, it was able to serve up at 15+ megs/second (so says adding the
speed reported by wget). The server never broke 7 megs of resident memory, and
tended to hang below 10% processor utilization.

There exists a live host running this web server: nada.ics.uci.edu
"""

import asynchat, asyncore, socket, SimpleHTTPServer
import sys, cgi, cStringIO, os, traceback, zlib, optparse

__version__ = ".4"

try:
    #Python 2.4 has a deque
    from collections import deque
except:
    #Python 2.3 and earlier don't
    #
    #limited deque, trimmed version of Raymond Hettinger's recipe:
    #http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/259179
    class deque(object):
        def __init__(self, iterable=()):
            self.left = self.right = 0
            self.data = {}
            self.extend(iterable)         
        
        def append(self, x):
            self.data[self.right] = x
            self.right += 1
        
        def appendleft(self, x):
            self.left -= 1        
            self.data[self.left] = x
        
        def pop(self):
            if self.left == self.right:
                raise IndexError('cannot pop from empty deque')
            self.right -= 1
            elem = self.data[self.right]
            del self.data[self.right]         
            return elem
        
        def popleft(self):
            if self.left == self.right:
                raise IndexError('cannot pop from empty deque')
            elem = self.data[self.left]
            del self.data[self.left]
            self.left += 1
            return elem
        
        def clear(self):
            self.data.clear()
            self.left = self.right = 0
        
        def extend(self, iterable):
            for elem in iterable:
                self.append(elem)
        
        def __len__(self):
            return self.right - self.left

reserved_names = dict.fromkeys(('com1 com2 com3 com4 com5 com6 com7 com8 com9 '
                                'lpt1 lpt2 lpt3 lpt4 lpt5 lpt6 lpt7 lpt8 lpt9 '
                                'con nul prn').split())

def popall(self):
    #Preallocate the list to save memory resizing.
    r = len(self)*[None]
    for i in xrange(len(r)):
        r[i] = self.popleft()
    return r        

class writewrapper(object):
    def __init__(self, d, blocksize=4096):
        self.blocksize = blocksize
        self.d = d
    def write(self, data):
        if self.blocksize in (None, -1):
            self.d.append(data)
        else:
            BS = self.blocksize
            xtra = 0
            if len(data)%BS:
                xtra = len(data)%BS + BS
            buf = self.d
            for i in xrange(0, len(data)-xtra, BS):
                buf.append(data[i:i+BS])
            if xtra:
                buf.append(data[-xtra:])
#
class ParseHeaders(dict):
    if 1:
        """Replacement for the deprecated mimetools.Message class
        Works like a dictionary with case-insensitive keys"""

    def __init__(self, infile, *args):
        self._ci_dict = {}
        lines = infile.readlines()
        for line in lines:
            k,v=line.split(":",1)
            self._ci_dict[k.lower()] = self[k] = v.strip()
        self.headers = self.keys()
    
    def getheader(self,key,default=""):
        return self._ci_dict.get(key.lower(),default)
    
    def get(self,key,default=""):
        return self._ci_dict.get(key.lower(),default)
#
class RequestHandler(asynchat.async_chat, SimpleHTTPServer.SimpleHTTPRequestHandler):
    if 1:
        server_version = "SimpleAsyncHTTPServer/"+__version__
        protocol_version = "HTTP/1.1"
        MessageClass = ParseHeaders
        blocksize = 4096
        
        #In enabling the use of buffer objects by setting use_buffer to True,
        #any data block sent will remain in memory until it has actually been
        #sent.
        use_buffer = False
        use_favicon = True
    
    def __init__(self, conn, addr, server):
        asynchat.async_chat.__init__(self,conn)
        self.client_address = addr
        self.connection = conn
        self.server = server
        # set the terminator : when it is received, this means that the
        # http request is complete ; control will be passed to
        # self.found_terminator
        self.set_terminator ('\r\n\r\n')
        self.incoming = deque()
        self.outgoing = deque()
        self.rfile = None
        self.wfile = writewrapper(self.outgoing, -self.use_buffer or self.blocksize)
        self.found_terminator = self.handle_request_line
        self.request_version = "HTTP/1.1"
        self.code = None
        # buffer the response and headers to avoid several calls to select()

    def update_b(self, fsize):
        if fsize > 1048576:
            self.use_buffer = True
            self.blocksize = 131072
    
    def collect_incoming_data(self,data):
        """Collect the data arriving on the connexion"""
        if not data:
            self.ac_in_buffer = ""
            return
        self.incoming.append(data)

    def prepare_POST(self):
        """Prepare to read the request body"""
        bytesToRead = int(self.headers.getheader('content-length'))
        # set terminator to length (will read bytesToRead bytes)
        self.set_terminator(bytesToRead)
        self.incoming.clear()
        # control will be passed to a new found_terminator
        self.found_terminator = self.handle_post_data
    
    def handle_post_data(self):
        """Called when a POST request body has been read"""
        self.rfile = cStringIO.StringIO(''.join(popall(self.incoming)))
        self.rfile.seek(0)
        self.do_POST()
            
    def do_GET(self):
        """Begins serving a GET request"""

        # Check for query string in URL
        qspos = self.path.find('?')
        if qspos>=0:
            self.body = cgi.parse_qs(self.path[qspos+1:], keep_blank_values=1)
            self.path = self.path[:qspos]

        self.handle_data()
        
    def do_POST(self):
        """Begins serving a POST request. The request data must be readable
        on a file-like object called self.rfile"""
        ctype, pdict = cgi.parse_header(self.headers.getheader('content-type'))
        length = int(self.headers.getheader('content-length'))
        if ctype == 'multipart/form-data':
            self.body = cgi.parse_multipart(self.rfile, pdict)
        elif ctype == 'application/x-www-form-urlencoded':
            qs = self.rfile.read(length)
            self.body = cgi.parse_qs(qs, keep_blank_values=1)
        else:
            self.body = ''                   # Unknown content-type
        #self.handle_post_body()
        self.handle_data()

    def handle_data(self):
        """Class to override"""
        if self.use_favicon and self.path == '/favicon.ico':
            self.send_response(200)
            self.send_header("Content-type", 'text/html')
            self.send_header("Content-Length", len(favicon))
            self.end_headers()
            self.log_request(self.code, len(favicon))
            self.outgoing.append(favicon)
            self.outgoing.append(None)
            return
        
        f = self.send_head()
        if f:
            # do some special things with file objects so that we don't have
            # to read them all into memory at the same time...may leave a
            # file handle open for longer than is really desired, but it does
            # make it able to handle files of unlimited size.
            try:
                size = os.fstat(f.fileno())[6]
            except AttributeError:
                size = f.len
            self.update_b(size)
            self.log_request(self.code, size)
            self.outgoing.append(f)
        else:
            self.log_request(self.code)
        
        # signal the end of this request
        self.outgoing.append(None)

    def handle_request_line(self):
        """Called when the http request line and headers have been received"""
        # prepare attributes needed in parse_request()
        self.rfile = cStringIO.StringIO(''.join(popall(self.incoming)))
        self.rfile.seek(0)
        self.raw_requestline = self.rfile.readline()
        self.parse_request()

        if self.command in ['GET','HEAD']:
            # if method is GET or HEAD, call do_GET or do_HEAD and finish
            method = "do_"+self.command
            if hasattr(self,method):
                getattr(self,method)()
        elif self.command=="POST":
            # if method is POST, call prepare_POST, don't finish yet
            self.prepare_POST()
        else:
            self.send_error(501, "Unsupported method (%s)" %self.command)

    def end_headers(self):
        """Send the blank line ending the MIME headers, send the buffered
        response and headers on the connection"""
        if self.request_version != 'HTTP/0.9':
            self.outgoing.append("\r\n")

    def handle_error(self):
        traceback.print_exc(sys.stderr)
        self.close()

    def writable(self):
        return len(self.outgoing) and self.connected
    
    def handle_write(self):
        O = self.outgoing
        while len(O):
            a = O.popleft()
            #handle end of request disconnection
            if a is None:
                #Some clients have issues with keep-alive connections, or
                #perhaps I implemented them wrong.
                
                #If the user is running a Python version < 2.4.1, there is a
                #bug with SimpleHTTPServer:
                #    http://python.org/sf/1097597
                #So we should be closing anyways, even though the client will
                #claim a partial download, so as to prevent hung-connections.
                ## if self.close_connection:
                self.close()
                return
            #handle file objects
            elif hasattr(a, 'read'):
                _a, a = a, a.read(self.blocksize)
                if not a:
                    del _a
                    continue
                else:
                    O.appendleft(_a)
                    break
            #handle string/buffer objects
            elif len(a):
                break
        else:
            #if we get here, the outgoing deque is empty
            return
        #if we get here, 'a' is a string or buffer object of length > 0
        try:
            num_sent = self.send(a)
            if num_sent < len(a):
                if not num_sent:
                    # this is probably overkill, but it can save the
                    # allocations of buffers when they are enabled
                    O.appendleft(a)
                elif self.use_buffer:
                    O.appendleft(buffer(a, num_sent))
                else:
                    O.appendleft(a[num_sent:])

        except socket.error, why:
            if isinstance(why, (str, unicode)):
                self.log_error(why)
            elif isinstance(why, tuple) and isinstance(why[-1], (str, unicode)):
                self.log_error(why[-1])
            else:
                self.log_error(str(why))
            self.handle_error()
    
    def send_head(self):
        path = self.translate_path(self.path)
        if sys.platform == 'win32':
            if os.path.split(path)[1].lower().split('.')[0] in reserved_names:
                self.send_error(404, "File not found")
                return
        if os.path.isdir(path):
            if not self.path.endswith('/'):
                self.send_response(302)
                x = '<META HTTP-EQUIV="refresh" CONTENT="0;URL=%s/">'%self.path
                self.send_header("Content-Location", self.path + '/')
                self.send_header("Content-Length", len(x))
                self.end_headers()
                self.wfile.write(x)
                return None
        return SimpleHTTPServer.SimpleHTTPRequestHandler.send_head(self)
    
    def send_response(self, code, message=None):
        if self.code:
            return
        self.code = code
        if message is None:
            if code in self.responses:
                message = self.responses[code][0]
            else:
                message = ''
        if self.request_version != 'HTTP/0.9':
            self.wfile.write("%s %d %s\r\n" %
                             (self.protocol_version, code, message))
            # print (self.protocol_version, code, message)
        self.send_header('Server', self.version_string())
        self.send_header('Date', self.date_time_string())
    
    def log_message(self, format, *args):
        sys.stderr.write("%s - - [%s] %s \"%s\" \"%s\"\n" %
                         (self.address_string(),
                          self.log_date_time_string(),
                          format%args,
                          self.headers.get('referer', ''),
                          self.headers.get('user-agent', '')
                          ))
#
class OnlyExactFiles(RequestHandler):
    def send_head(self):
        path = self.translate_path(self.path)
        if os.path.isdir(path):
            self.send_error(404, "File not found")
            return None
        return RequestHandler.send_head(self)
#
class ExactFilesAndIndex(RequestHandler):
    def list_directory(self, path):
        self.send_error(404, "File not found")
        return None
#

class Server(asyncore.dispatcher):
    if 1:
        """Copied from http_server in medusa"""
    def __init__ (self, ip, port, handler):
        self.ip = ip
        self.port = port
        self.handler = handler
        asyncore.dispatcher.__init__ (self)
        self.create_socket (socket.AF_INET, socket.SOCK_STREAM)

        self.set_reuse_addr()
        self.bind ((ip, port))

        # Quoting the socket module documentation...
        # listen(backlog)
        #     Listen for connections made to the socket. The backlog argument
        #     specifies the maximum number of queued connections and should
        #     be at least 1; the maximum value is system-dependent (usually
        #     5).
        self.listen (5)

    def handle_accept (self):
        try:
            conn, addr = self.accept()
        except socket.error:
            self.log_info ('warning: server accept() threw an exception', 'warning')
            return
        except TypeError:
            self.log_info ('warning: server accept() threw EWOULDBLOCK', 'warning')
            return
        # creates an instance of the handler class to handle the request/response
        # on the incoming connexion
        self.handler(conn,addr,self)

favicon = zlib.decompress(
'x\x9c\xb5\x93\xcdN\xdb@\x14\x85\x07\x95\x07\xc8\x8amYv\xc9#\xe4\x11x\x04\x96}'
'\x8c\x88\x1dl\xa0\x9b\xb6A\xa2)\x0bVTB\xa9"\xa5?*I\x16\xad"\x84d\x84DE\x93'
'\x14;v\xc01M\xe2$\x988\xb1l\x9d\xde;v\\\x03\x89TU\xea\xb5N\xe4\xb9\x9a\xef'
'\x1c\xcfO\x84X\xa0\'\x95\x12\xf4\xbb,\x9e/\n\xb1$\x84xF\xa2\x16u\xc2>WzQ\xfc'
'\xf7\xca\xad\xafo\x91T\xd2\x1ai\xe5\x1fx[\xf9\xf4\x01\xc57\xbb\xd8\xdf\xd8'
'\x00\x8d\x11\xf9\x95\x12\xda\x9a\xc3\xae\xe5_\xbdDpk\x03\xc3\xaeT\xd0\xb3\xd0'
'>?\x83Z\xfd\x86Z\xa5\x84\x1fG_\xa4\xe7\x1c^\xa9W\xbfJ\xfe\xb4\xf0\x0e^\xdb'
'\x88}0 \xafA\x0f\xa3+c&O\xbd\xf4\xc1\xf6\xb6d\x9d\xc6\x05\xdcVSz\xb0x\x1c\x10'
'\x0fo\x02\xc7\xd0\xe7\xf1%\xe5\xf3\xc78\xdb\xf9Y\x93\x1eI\x1f\xf8>\xfa\xb5'
'\x8bG<\x8dW\x0f^\x84\xd9\xee\xb5~\x8f\xe1w\xaf{\x83\x80\xb2\xbd\xe1\x10\x83'
'\x88\'\xa5\x12\xbcZ?9\x8e\xb3%\xd3\xeb`\xd4\xd2\xffdS\xb9\x96\x89!}W!\xfb\x9a'
'\xf9t\xc4f\x8aos\x92\x9dtn\xe0\xe8Z\xcc\xc8=\xec\xf7d6\x97\xa3]\xc2Q\x1b(\xec'
'd\x99_\x8dx\xd4\x15%\xce\x96\xf9\xbf\xacP\xd1:\xfc\xf1\x18\xbe\xeb\xe2\xaey'
'\x89;]\xc5\xf1\xfb<\xf3\x99\xe9\x99\xefon\xa2\xdb6\xe5\x1c\xbb^\x8b}FV\x1b'
'\x9es+\xb3\xbd\x81M\xeb\xd1\xe0^5\xf1\xbd|\xc4\xfca\xf2\xde\xf0w\x9cW\xabr.'
'\xe7\xd9\x8dFx\x0e\xa6){\x93\x8e\x85\xf1\xb5\x81\x89\xd9\x82\xa1\x9c\xc8;\xf9'
'\xe0\x0cV\xb8W\xdc\xdb\x83\xa9i\xb1O@g\xa6T*\xd3=O\xeaP\xcc(^\x17\xfb\xe4\xb3'
'Y\xc9\xb1\x17{N\xf7\xfbo\x8b\xf7\x97\x94\xe3;\xcd\xff)\xd2\xf2\xacy\xa0\x9b'
'\xd4g=\x11B\x8bT\x8e\x94Y\x08%\x12\xe2q\x99\xd4\x7f*\x84O\xfa\r\xb5\x916R'
)

which = (RequestHandler, OnlyExactFiles, ExactFilesAndIndex)

class to_logfile:
    if 1:
        fl = True
    def __init__(self, fileobj):
        self.f = fileobj
    def write(self, data):
        data = data.encode('utf-8')
        sys.__stdout__.write(data)
        self.f.write(data)
        if self.fl:
            self.f.flush()

if __name__=="__main__":
    usage = "usage: \%prog -r<root> [-p<port>] [-0|-1|-2]"
    
    parser = optparse.OptionParser(usage)
    parser.add_option('-r', '--root', dest='root',
                      help='Root path of the web server', action='store')
    parser.add_option('-p', '--port', dest='port', type='int',
                      help='Port to listen on (default 80)', default=80, action='store')
    parser.add_option('-0', dest='server', help='Run the standard server (default)',
                      action='store_const', const=0, default=0)
    parser.add_option('-1', dest='server',
                      help='Run the server which only serves exact file names specified',
                      action='store_const', const=1)
    parser.add_option('-2', dest='server',
                      help='Run the server which will serve exact files and directory->index files',
                      action='store_const', const=2)
    
    options, args = parser.parse_args()
    
    if options.root is None:
        parser.error("Need root path to start server")
    
    if not os.path.isdir(options.root):
        parser.error("Root path does not exist")
    
    os.chdir(options.root)
    
    req_handler = which[options.server]
    s=Server('',options.port,req_handler)
    print req_handler.__name__, "running on port", options.port, "with root path", options.root
    asyncore.loop()