Modules/Azure/Scaffolding/Python/WebRole/wfastcgi.py

 # ############################################################################
 #
 # Copyright (c) Microsoft Corporation. 
 #
 # This source code is subject to terms and conditions of the Apache License, Version 2.0. A 
 # copy of the license can be found in the License.html file at the root of this distribution. If 
 # you cannot locate the Apache License, Version 2.0, please send an email to 
 # vspython@microsoft.com. By using this source code in any fashion, you are agreeing to be bound 
 # by the terms of the Apache License, Version 2.0.
 #
 # You must not remove this notice, or any other, from this software.
 #
 # ###########################################################################

import sys
import struct
import cStringIO
import os
import traceback
from os import path
from xml.dom import minidom

# http://www.fastcgi.com/devkit/doc/fcgi-spec.html#S3

FCGI_VERSION_1 = 1
FCGI_HEADER_LEN = 8
 
FCGI_BEGIN_REQUEST       = 1
FCGI_ABORT_REQUEST       = 2
FCGI_END_REQUEST         = 3
FCGI_PARAMS              = 4
FCGI_STDIN               = 5
FCGI_STDOUT              = 6
FCGI_STDERR              = 7
FCGI_DATA                = 8
FCGI_GET_VALUES          = 9
FCGI_GET_VALUES_RESULT  = 10
FCGI_UNKNOWN_TYPE       = 11
FCGI_MAXTYPE = FCGI_UNKNOWN_TYPE

FCGI_NULL_REQUEST_ID    = 0

FCGI_KEEP_CONN = 1

FCGI_RESPONDER  = 1
FCGI_AUTHORIZER = 2
FCGI_FILTER     = 3

FCGI_REQUEST_COMPLETE = 0
FCGI_CANT_MPX_CONN    = 1
FCGI_OVERLOADED       = 2
FCGI_UNKNOWN_ROLE     = 3

FCGI_MAX_CONNS  = "FCGI_MAX_CONNS"
FCGI_MAX_REQS   = "FCGI_MAX_REQS"
FCGI_MPXS_CONNS = "FCGI_MPXS_CONNS"

class FastCgiRecord(object):
    """Represents a FastCgiRecord.  Encapulates the type, role, flags.  Holds
onto the params which we will receive and update later."""
    def __init__(self, type, req_id, role, flags):
        self.type = type
        self.req_id = req_id
        self.role = role
        self.flags = flags
        self.params = {}
        
    def __repr__(self):
        return '<FastCgiRecord(%d, %d, %d, %d)>' % (self.type, 
                                                    self.req_id, 
                                                    self.role, 
                                                    self.flags)

#typedef struct {
#   unsigned char version;
#   unsigned char type;
#   unsigned char requestIdB1;
#   unsigned char requestIdB0;
#   unsigned char contentLengthB1;
#   unsigned char contentLengthB0;
#   unsigned char paddingLength;
#   unsigned char reserved;
#   unsigned char contentData[contentLength];
#   unsigned char paddingData[paddingLength];
#} FCGI_Record;

def read_fastcgi_record(input):
    """reads the main fast cgi record"""
    data = input.read(8)     # read record
    content_size = ord(data[4]) << 8 | ord(data[5])

    content = input.read(content_size)  # read content    
    input.read(ord(data[6]))     # read padding

    if ord(data[0]) != FCGI_VERSION_1:
        raise Exception('Unknown fastcgi version ' + str(data[0]))

    req_id = (ord(data[2]) << 8) | ord(data[3])
    
    reqtype = ord(data[1])
    processor = REQUEST_PROCESSORS.get(reqtype)
    if processor is None:
        # unknown type requested, send response
        send_response(req_id, FCGI_UNKNOWN_TYPE, data[1] + '\0' * 7)
        return None

    return processor(req_id, content)


def read_fastcgi_begin_request(req_id, content):
    """reads the begin request body and updates our
_REQUESTS table to include the new request"""
    #    typedef struct {
    #        unsigned char roleB1;
    #        unsigned char roleB0;
    #        unsigned char flags;
    #        unsigned char reserved[5];
    #    } FCGI_BeginRequestBody;

    # TODO: Ignore request if it exists    
    res = FastCgiRecord(
        FCGI_BEGIN_REQUEST,
        req_id,
        (ord(content[0]) << 8) | ord(content[1]),   # role
        ord(content[2]),  # flags
    )
    _REQUESTS[req_id] = res    


def read_fastcgi_keyvalue_pairs(content, offset):
    """Reads a FastCGI key/value pair stream"""

    name_len = ord(content[offset])

    if (name_len & 0x80) != 0:
        name_full_len = chr(name_len & ~0x80) + content[offset + 1:offset+4]
        name_len = int_struct.unpack(name_full_len)[0]
        offset += 4
    else:
        offset += 1
    
    value_len = ord(content[offset])

    if (value_len & 0x80) != 0:
        value_full_len = chr(value_len & ~0x80) + content[offset+1:offset+4]
        value_len = int_struct.unpack(value_full_len)[0]
        offset += 4
    else:
        offset += 1

    name = content[offset:offset+name_len]
    offset += name_len
    
    value = content[offset:offset+value_len]
    offset += value_len

    return offset, name, value


def write_name_len(io, name):
    """Writes the length of a single name for a key or value in
a key/value stream"""
    if len(name) <= 0x7f:
        io.write(chr(len(name)))
    else:
        io.write(int_struct.pack(len(name)))


def write_fastcgi_keyvalue_pairs(pairs):
    """creates a FastCGI key/value stream and returns it as a string"""
    res = cStringIO.StringIO()
    for key, value in pairs.iteritems():
        write_name_len(res, key)
        write_name_len(res, value)
        
        res.write(key)
        res.write(value)

    return res.getvalue()


def read_fastcgi_params(req_id, content):
    if not content:
        return None

    offset = 0
    res = _REQUESTS[req_id].params
    while offset < len(content):
        offset, name, value = read_fastcgi_keyvalue_pairs(content, offset)
        res[name] = value


def read_fastcgi_input(req_id, content):
    """reads FastCGI std-in and stores it in wsgi.input passed in the
wsgi environment array"""
    res = _REQUESTS[req_id].params
    if 'wsgi.input' not in res:
        res['wsgi.input'] = content
    else:
        res['wsgi.input'] += content

    if not content:
        # we've hit the end of the input stream, time to process input...
        return _REQUESTS[req_id]


def read_fastcgi_data(req_id, content):
    """reads FastCGI data stream and publishes it as wsgi.data"""
    res = _REQUESTS[req_id].params
    if 'wsgi.data' not in res:
        res['wsgi.data'] = content
    else:
        res['wsgi.data'] += content


def read_fastcgi_abort_request(req_id, content):
    """reads the wsgi abort request, which we ignore, we'll send the
finish execution request anyway..."""
    pass


def read_fastcgi_get_values(req_id, content):
    """reads the fastcgi request to get parameter values, and immediately 
responds"""
    offset = 0
    request = {}
    while offset < len(content):
        offset, name, value = read_fastcgi_keyvalue_pairs(content, offset)
        request[name] = value

    response = {}
    if FCGI_MAX_CONNS in request:
        response[FCGI_MAX_CONNS] = '1'

    if FCGI_MAX_REQS in request:
        response[FCGI_MAX_REQS] = '1'

    if FCGI_MPXS_CONNS in request:
        response[FCGI_MPXS_CONNS] = '0'

    send_response(req_id, FCGI_GET_VALUES_RESULT, 
                  write_fastcgi_keyvalue_pairs(response))


# Formatting of 4-byte ints in network order
int_struct = struct.Struct('!i')

# Our request processors for different FastCGI protocol requests.  Only
# the requests which we receive are defined here.
REQUEST_PROCESSORS = {
    FCGI_BEGIN_REQUEST : read_fastcgi_begin_request,
    FCGI_ABORT_REQUEST : read_fastcgi_abort_request,
    FCGI_PARAMS : read_fastcgi_params,
    FCGI_STDIN : read_fastcgi_input,
    FCGI_DATA : read_fastcgi_data,
    FCGI_GET_VALUES : read_fastcgi_get_values
}

def log(txt):
    """Logs fatal errors to a log file if WSGI_LOG env var is defined"""
    log_file = os.environ.get('WSGI_LOG')
    if log_file:
        with file(log_file, 'a+') as f:
            f.write(txt)


def send_response(id, resp_type, content, streaming = True):
    """sends a response w/ the given id, type, and content to the server.
If the content is streaming then an empty record is sent at the end to 
terminate the stream"""
    offset = 0
    while 1:
        if id < 256:
            id_0 = 0
            id_1 = id
        else:
            id_0 = id >> 8
            id_1 = id & 0xff
    
        # content len, padding len, content
        len_remaining = len(content) - offset
        if len_remaining > 65535:
            len_0 = 0xff
            len_1 = 0xff
            content_str = content[offset:offset+65535]
            offset += 65535
        else:
            len_0 = len_remaining >> 8
            len_1 = len_remaining & 0xff
            content_str = content[offset:]
            offset += len_remaining

        data = '%c%c%c%c%c%c%c%c%s' % (
                FCGI_VERSION_1,     # version
                resp_type,          # type
                id_0,               # requestIdB1
                id_1,               # requestIdB0
                len_0,              # contentLengthB1
                len_1,              # contentLengthB0
                0,                  # paddingLength
                0,                  # reserved
                content_str)

        os.write(stdout, data)
        if len_remaining == 0 or not streaming:
            break

def update_environment():
    cur_dir = path.dirname(path.dirname(__file__))
    web_config = path.join(cur_dir, 'Web.config')
    if os.path.exists(web_config):
        try:
            with file(web_config) as wc:
                doc = minidom.parse(wc)
                config = doc.getElementsByTagName('configuration')
                for configSection in config:
                    appSettings = configSection.getElementsByTagName('appSettings')
                    for appSettingsSection in appSettings:
                        values = appSettingsSection.getElementsByTagName('add')
                        for curAdd in values:
                            key = curAdd.getAttribute('key')
                            value = curAdd.getAttribute('value')
                            if key and value:
                                os.environ[key] = value
        except:
            # unable to read file
            log(traceback.format_exc())
            pass


if __name__ == '__main__':
    handler_name = os.getenv('WSGI_HANDLER', 'django.core.handlers.wsgi.WSGIHandler()')
    module, callable = handler_name.rsplit('.', 1)
    if callable.endswith('()'):
        callable = callable.rstrip('()')
        handler = getattr(__import__(module, fromlist=[callable]), callable)()
    else:
        handler = getattr(__import__(module, fromlist=[callable]), callable)

    stdout = sys.stdin.fileno()
    try:
        import msvcrt
        msvcrt.setmode(sys.stdin.fileno(), os.O_BINARY)
    except ImportError:
        pass

    update_environment()

    _REQUESTS = {}

    while True:
        try:
            record = read_fastcgi_record(sys.stdin)
            if record:
                record.params['wsgi.input'] = cStringIO.StringIO(record.params['wsgi.input'])
                record.params['wsgi.version'] = (1,0)
                record.params['wsgi.url_scheme'] = 'https' if record.params.has_key('HTTPS') and record.params['HTTPS'].lower() == 'on' else 'http'
                record.params['wsgi.multiprocess'] = True
                record.params['wsgi.multithread'] = False
                record.params['wsgi.run_once'] = False

                def start_response(status, headers, exc_info = None):
                    global response_headers, status_line
                    response_headers = headers
                    status_line = status
                
                errors = sys.stderr = sys.__stderr__ = record.params['wsgi.errors'] = cStringIO.StringIO()
                sys.stdout = sys.__stdout__ = cStringIO.StringIO()
                record.params['SCRIPT_NAME'] = ''
                try:
                    response = ''.join(handler(record.params, start_response))
                except:
                    send_response(record.req_id, FCGI_STDERR, errors.getvalue())
                else:
                    status = 'Status: ' + status_line + '\r\n'
                    headers = ''.join('%s: %s\r\n' % (name, value) for name, value in response_headers)
                    full_response = status + headers + '\r\n' + response
                    send_response(record.req_id, FCGI_STDOUT, full_response)

                # for testing of throughput of fastcgi handler vs static pages
                #send_response(record.req_id, FCGI_STDOUT, 'Content-type: text/html\r\n\r\n\r\n<html>\n<body>bar</body></html>')

                send_response(record.req_id, FCGI_END_REQUEST, '\x00\x00\x00\x00\x00\x00\x00\x00', streaming=False)
                del _REQUESTS[record.req_id]
        except:
            log(traceback.format_exc())