Login

django under apache / mod_fcgid

Author:
mike_45
Posted:
February 3, 2009
Language:
Python
Version:
1.0
Score:
2 (after 2 ratings)

This recipe uses a modified version of Robin Dunn's fcgi.py module that adapts fcgi to wsgi and lets you run Django under mod_fcgid. One good thing about mod_fcgid is that it does all process management for you, which makes this setup quite straightforward.

Also, since Robin's module works both in a cgi and fcgi context, switching a django site between cgi and fastcgi is a one-liner in the apache config, without any changes to python code or django config. CGI may be handy for development, since it loads all code (including changed code) on every request, yet lets you work in an environment that resembles production.

Apache configuration examples are found in the comment at the beginning of the python module.

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
#!/usr/bin/python
'''
FcgiWsgiAdapter.py

serves wsgi requests over fcgi. Basic usage in wsgi script:

from FcgiWsgiAdapter import serve
serve(myWsgiApp)

The fcgi part of this was adopted wholesale, with minor modifications, 
from Robin Dunn's fastcgi module; the original preamble of that module 
is further down.
---
To use with django and mod_fcgid, you need a cgi script, say django.cgi:

#!/usr/bin/python
from FcgiWsgiAdapter import list_environment, serve_wsgi

import os, sys
os.environ['DJANGO_SETTINGS_MODULE'] = 'settings'  # or whatever
from django.core.handlers.wsgi import WSGIHandler

# use this to test that fastcgi works and to inspect the environment
# serve_wsgi(list_environment)
# use this to serve django
serve_wsgi(WSGIHandler())
-----
Apache config example:

RewriteRule ^/(~[^/]+)/django/(.*)$ /$1/django/django.cgi/$2 [PT]
<Directory /home/*/public_html/django/>
    Options ExecCGI
    AddHandler fcgid-script .cgi
    # AddHandler cgi-script .cgi
</Directory>

This would invoke django for any "/~joe/django/joes_app" request.
This configuration example also works with suexec, which would be 
useful in a multi-user context. 

Commenting out fcgid-script and uncommenting cgi-script (and a 
server restart) will switch the execution mode from fastcgi 
to plain cgi, without any further changes being required 
anywhere else.

For simpler urls when serving a single site, you could do

RewriteRule ^/mysite/(.*)$ /~fakeuser/django/django.cgi/$1 [PT]
<Directory /home/fakeuser/public_html/django/>
    Options ExecCGI
    AddHandler fcgid-script .cgi
</Directory>

This config would still give you suexec in a typical apache 
install, since [PT] applies the output of mod_rewrite to 
suexec and ~fakeuser is a user directory, which suexec likes.
'''

#
#               Copyright (c) 1998 by Total Control Software
#                         All Rights Reserved
#
#
# Module Name:  fcgi.py
#
# Description:  Handles communication with the FastCGI module of the
#               web server without using the FastCGI developers kit, but
#               will also work in a non-FastCGI environment, (straight CGI.)
#               This module was originally fetched from someplace on the
#               Net (I don't remember where and I can't find it now...) and
#               has been significantly modified to fix several bugs, be more
#               readable, more robust at handling large CGI data and return
#               document sizes, and also to fit the model that we had previously
#               used for FastCGI.
#
#     WARNING:  If you don't know what you are doing, don't tinker with this
#               module!
#
# Creation Date:    1/30/98 2:59:04PM
#
# License:      This is free software.  You may use this software for any
#               purpose including modification/redistribution, so long as
#               this header remains intact and that you do not claim any
#               rights of ownership or authorship of this software.  This
#               software has been tested, but no warranty is expressed or
#               implied.
#
#

# minor modifications by Michael Palmer:
# - reduce string copying operations when writing output
# - some updates to more recent python syntax


import  os, sys, string, socket, errno, traceback
from    cStringIO   import StringIO

from wsgiref.handlers import BaseCGIHandler

#

# Set various FastCGI constants
# Maximum number of requests that can be handled
FCGI_MAX_REQS=1
FCGI_MAX_CONNS = 1

# Supported version of the FastCGI protocol
FCGI_VERSION_1 = 1

# Boolean: can this application multiplex connections?
FCGI_MPXS_CONNS=0

# Record types
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

# Types of management records
ManagementTypes = [FCGI_GET_VALUES]

FCGI_NULL_REQUEST_ID=0

# Masks for flags component of FCGI_BEGIN_REQUEST
FCGI_KEEP_CONN = 1

# Values for role component of FCGI_BEGIN_REQUEST
FCGI_RESPONDER = 1 ; FCGI_AUTHORIZER = 2 ; FCGI_FILTER = 3

# Values for protocolStatus component of FCGI_END_REQUEST
FCGI_REQUEST_COMPLETE = 0               # Request completed nicely
FCGI_CANT_MPX_CONN    = 1               # This app can't multiplex
FCGI_OVERLOADED       = 2               # New request rejected; too busy
FCGI_UNKNOWN_ROLE     = 3               # Role value not known

# chunk size for writing data
CHUNK_SIZE = 2**13  # 8 kB - tried 64 kB but it fucks up. 8 kB is fast enough.

error = 'fcgi.error'

# The following function is used during debugging; it isn't called
# anywhere at the moment

def error(msg):
    "Append a string to /tmp/err"
    errf=open('/tmp/err', 'a+')
    errf.write(msg +'\n')
    errf.close()

class record:
    "Class representing FastCGI records"
    def __init__(self):
        self.version = FCGI_VERSION_1
        self.recType = FCGI_UNKNOWN_TYPE
        self.reqId   = FCGI_NULL_REQUEST_ID
        self.content = ""

    #
    def readRecord(self, sock):
        s = map(ord, sock.recv(8))
        self.version, self.recType, paddingLength = s[0], s[1], s[6]
        self.reqId, contentLength = (s[2]<<8)+s[3], (s[4]<<8)+s[5]
        self.content = ""
        while len(self.content) < contentLength:
            data = sock.recv(contentLength - len(self.content))
            self.content = self.content + data
        if paddingLength != 0:
            padding = sock.recv(paddingLength)

        # Parse the content information
        c = self.content
        if self.recType == FCGI_BEGIN_REQUEST:
            self.role = (ord(c[0])<<8) + ord(c[1])
            self.flags = ord(c[2])

        elif self.recType == FCGI_UNKNOWN_TYPE:
            self.unknownType = ord(c[0])

        elif self.recType == FCGI_GET_VALUES or self.recType == FCGI_PARAMS:
            self.values={}
            pos=0
            while pos < len(c):
                name, value, pos = readPair(c, pos)
                self.values[name] = value
        elif self.recType == FCGI_END_REQUEST:
            b = map(ord, c[0:4])
            self.appStatus = (b[0]<<24) + (b[1]<<16) + (b[2]<<8) + b[3]
            self.protocolStatus = ord(c[4])

    #
    def writeRecord(self, sock):
        content = self.content
        if self.recType == FCGI_BEGIN_REQUEST:
            content = chr(self.role>>8) + chr(self.role & 255) + chr(self.flags) + 5*'\000'

        elif self.recType == FCGI_UNKNOWN_TYPE:
            content = chr(self.unknownType) + 7*'\000'

        elif self.recType==FCGI_GET_VALUES or self.recType==FCGI_PARAMS:
            content = ""
            for i in self.values.keys():
                content = content + writePair(i, self.values[i])

        elif self.recType==FCGI_END_REQUEST:
            v = self.appStatus
            content = chr((v>>24)&255) + chr((v>>16)&255) + chr((v>>8)&255) + chr(v&255)
            content = content + chr(self.protocolStatus) + 3*'\000'

        cLen = len(content)
        eLen = (cLen + 7) & (0xFFFF - 7)    # align to an 8-byte boundary
        padLen = eLen - cLen

        hdr = [ self.version,
                self.recType,
                self.reqId >> 8,
                self.reqId & 255,
                cLen >> 8,
                cLen & 255,
                padLen,
                0]
        # hdr = string.joinfields(map(chr, hdr), '')
        hdr = ''.join([chr(h) for h in hdr])

        sock.send(hdr + content + padLen*'\000')

#

def readPair(s, pos):
    nameLen = ord(s[pos])
    pos += 1

    if nameLen & 128:
        b = [ord(x) for x in s[pos:pos+3]]
        pos += 3
        nameLen = ((nameLen&127)<<24) + (b[0]<<16) + (b[1]<<8) + b[2]

    valueLen = ord(s[pos])
    pos += 1

    if valueLen & 128:
        b = [ord(x) for x in s[pos:pos+3]]
        pos += 3
        valueLen=((valueLen&127)<<24) + (b[0]<<16) + (b[1]<<8) + b[2]

    return ( s[pos:pos+nameLen], s[pos+nameLen:pos+nameLen+valueLen],
             pos+nameLen+valueLen )



def writePair(name, value):
    l=len(name)
    if l<128: s=chr(l)
    else:
        s=chr(128|(l>>24)&255) + chr((l>>16)&255) + chr((l>>8)&255) + chr(l&255)
    l=len(value)
    if l<128: s=s+chr(l)
    else:
        s=s+chr(128|(l>>24)&255) + chr((l>>16)&255) + chr((l>>8)&255) + chr(l&255)
    return s + name + value

#

def HandleManTypes(r, conn):
    if r.recType == FCGI_GET_VALUES:
        r.recType = FCGI_GET_VALUES_RESULT
        v={}
        vars={'FCGI_MAX_CONNS' : FCGI_MAX_CONNS,
              'FCGI_MAX_REQS'  : FCGI_MAX_REQS,
              'FCGI_MPXS_CONNS': FCGI_MPXS_CONNS}
        for i in r.values.keys():
            if vars.has_key(i): v[i]=vars[i]
        r.values=vars
        r.writeRecord(conn)

#
#


_isFCGI = 1         # assume it is until we find out for sure

def isFCGI():
    global _isFCGI
    return _isFCGI

#


fcgi_init = None
_sock = None

class FCGI:
    def __init__(self):
        self.haveFinished = 0
        if fcgi_init == None:
            _startup()
        if not isFCGI():
            self.haveFinished = 1
            self.inp, self.out, self.err, self.env = \
                                sys.stdin, sys.stdout, sys.stderr, os.environ
            return

        if os.environ.has_key('FCGI_WEB_SERVER_ADDRS'):
            good_addrs=string.split(os.environ['FCGI_WEB_SERVER_ADDRS'], ',')
            good_addrs=map(string.strip(good_addrs))        # Remove whitespace
        else:
            good_addrs=None

        self.conn, addr=_sock.accept()
        stdin, data="", ""
        self.env = {}
        self.requestId=0
        remaining=1

        # Check if the connection is from a legal address
        if good_addrs!=None and addr not in good_addrs:
            raise error, 'Connection from invalid server!'

        while remaining:
            r = record()
            r.readRecord(self.conn)

            if r.recType in ManagementTypes:
                HandleManTypes(r, self.conn)

            elif r.reqId==0:
                # Oh, poopy.  It's a management record of an unknown
                # type.  Signal the error.
                r2 = record()
                r2.recType = FCGI_UNKNOWN_TYPE ; r2.unknownType=r.recType
                r2.writeRecord(self.conn)
                continue                # Charge onwards

            # Ignore requests that aren't active
            elif r.reqId != self.requestId and r.recType != FCGI_BEGIN_REQUEST:
                continue

            # If we're already doing a request, ignore further BEGIN_REQUESTs
            elif r.recType == FCGI_BEGIN_REQUEST and self.requestId != 0:
                continue

            # Begin a new request
            if r.recType == FCGI_BEGIN_REQUEST:
                self.requestId = r.reqId
                if r.role == FCGI_AUTHORIZER:   remaining=1
                elif r.role == FCGI_RESPONDER:  remaining=2
                elif r.role == FCGI_FILTER:     remaining=3

            elif r.recType == FCGI_PARAMS:
                if r.content == "":
                    remaining=remaining-1
                else:
                    for i in r.values.keys():
                        self.env[i] = r.values[i]

            elif r.recType == FCGI_STDIN:
                if r.content == "":
                    remaining=remaining-1
                else:
                    stdin=stdin+r.content

            elif r.recType==FCGI_DATA:
                if r.content == "":
                    remaining=remaining-1
                else:
                    data=data+r.content
        # end of while remaining:

        self.inp = sys.stdin  = StringIO(stdin)
        self.err = sys.stderr = StringIO()
        self.out = sys.stdout = StringIO()
        #self.data = StringIO(data)

    #def __del__(self): I really don't get what this is good for...
        #self.finish()

    def finish(self, status=0):
        if not self.haveFinished:
            self.haveFinished = 1

            self.err.seek(0,0)
            self.out.seek(0,0)

            r=record()
            r.recType = FCGI_STDERR
            r.reqId = self.requestId
            data = self.err.read()

            chunker = self.datachunker(data)
            for chunk in chunker:
                r.content = chunk
                r.writeRecord(self.conn)
            r.content="" ; r.writeRecord(self.conn)      # Terminate stream

            r.recType = FCGI_STDOUT
            data = self.out.read()

            chunker = self.datachunker(data)

            for chunk in chunker:
                r.content = chunk
                r.writeRecord(self.conn)
            r.content="" ; r.writeRecord(self.conn)      # Terminate stream

            r=record()
            r.recType=FCGI_END_REQUEST
            r.reqId=self.requestId
            r.appStatus=status
            r.protocolStatus=FCGI_REQUEST_COMPLETE
            r.writeRecord(self.conn)
            self.conn.close()
        elif not isFCGI():   # for some reason cgi repeats again and again if we don't do this.
            sys.exit()

    def datachunker(self, data):
        '''
        yield string in chunks for writing
        '''
        c = 0
        cs = CHUNK_SIZE
        d = data[c:c + cs]
        if d:
            c += cs
            yield d
        else:
            raise StopIteration


def _startup():
    global fcgi_init
    fcgi_init = 1
    try:
        s=socket.fromfd(sys.stdin.fileno(), socket.AF_INET,
                        socket.SOCK_STREAM)
        s.getpeername()
    except socket.error, (err, errmsg):
        if err != errno.ENOTCONN:       # must be a non-fastCGI environment
            global _isFCGI
            _isFCGI = 0
            return

    global _sock
    _sock = s


#--------------------------------------------------------------------
# the code below is not part of the original fcgi.py module; it builds
# on the fcgi.py code to run wsgi applications.

# show full traceback if request originated from any of these ips
SHOW_TRACEBACK_IPS = ['127.0.0.1']

class FCGIHandler(BaseCGIHandler):
    '''
    handle a single request received through fcgi
    '''
    wsgi_multithread = False    # the underlying fcgi module is not threaded
    wsgi_multiprocess = True    # might be wrong, depending on your config
    wsgi_run_once = False       # ... likewise
    origin_server = False       # We are not transmitting direct to client, so won't
                                # send http status line and protocol information

    def __init__(self, request):
        BaseCGIHandler.__init__(self, request.inp, request.out, request.err, request.env, \
                                      multithread=self.wsgi_multithread, \
                                      multiprocess=self.wsgi_multiprocess)

    # error handling. this is sent to the client by wsgiref.basehandler.

    def error_output(self, environ, start_response):
        '''
        show traceback if we are so entitled.
        '''
        start_response(self.error_status, self.error_headers[:], sys.exc_info())
        if self.environ.get('REMOTE_ADDR') in SHOW_TRACEBACK_IPS:
            err = traceback.format_exc()
        else:
            err = self.error_body
        return ['wsgi app execution error\n', '-' * 24, '\n', err]


    def run(self, application):
        '''
        Invoke the application
        '''
        self.setup_environ()
        self.result = application(self.environ, self.start_response)
        self.finish_response()


def serve_wsgi(app, handlerClass=FCGIHandler):
    '''
    run (wsgi) app on each incoming FCGI request.
    '''
    while True:
        req = FCGI()
        h = handlerClass(req)
        h.run(app)
        req.finish()
        del req

#------------------------------------------------
# test the thing...
def list_environment(environ, start_response):
    '''
    Simple WSGI test application - just display the wsgi environment.
    Kinda useful, too for debugging.
    '''
    status = '200 OK'
    response_headers = [('Content-type','text/plain')]
    start_response(status, response_headers)
    out = ['FcgiWsgiAdapter test output (just a listing of the WSGI environment)\n']
    out.append('-' * (len(out[0]) -1)  + '\n')

    for k,v in sorted(environ.items()):
        out.extend([k.ljust(25), ': ', str(v).strip(), '\n'])

    return out


def test():
    '''
    to run this, import and run in an actual cgi or fcgi script
    '''
    serve_wsgi(list_environment)

More like this

  1. Template tag - list punctuation for a list of items by shapiromatron 10 months ago
  2. JSONRequestMiddleware adds a .json() method to your HttpRequests by cdcarter 10 months, 1 week ago
  3. Serializer factory with Django Rest Framework by julio 1 year, 4 months ago
  4. Image compression before saving the new model / work with JPG, PNG by Schleidens 1 year, 5 months ago
  5. Help text hyperlinks by sa2812 1 year, 6 months ago

Comments

dvd (on March 30, 2009):

The datachunker method emit only one chunk, I think it should be something like this:

def datachunker(self, data):
    '''
    yield string in chunks for writing
    '''
    c = 0
    cs = CHUNK_SIZE
    d = data[c:c + cs]
    while d:
        yield d
        c += cs
        d = data[c:c + cs]

#

Please login first before commenting.