Begin forwarded message: Date: October 13, 2010 7:20:20 PM GMT+02:00
Subject: Re: [Twisted-Python] _twistd_unix.py / daemonize() / OSX / USING_FORK_WITHOUT_EXEC_IS_NOT_SUPPORTED_BY_FILE_MANAGER
On Oct 13, 2010, at 12:05 PM, Erik van Blokland wrote:
On Oct 13, 2010, at 5:52 PM, Phil Mayers wrote:
Other info indicates this is Apple trying to be clever and "protect"
applications from some signal handling issues surrounding fork() with
libraries which aren't safe in that situation; presumably these are
MacOS-specific libraries?
If this really is true, then MacOS X is no longer posix-compliant in
those circumstances, and Twisted is going to need some work :o(
Can you share more details about the application; the context in which
it is started, and which system libraries it's likely to load?
Here's a compact version. The script uses OSX' Quartz to create and manipulate images. Twisted is used to wrap it as a webserver, images are served. More pointers on how to start and use it in the script itself.
You need to avoid using or importing any OSX APIs until after the daemonization has occurred. Unfortunately, twisted executes the entire script file before daemonizing. [that's unfortunate for other reasons besides this, too] Here's a corrected version of your script which works properly. It defers importing Quartz until the reactor is running, by moving it into a function called by reactor.callWhenRunning().
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#!/usr/bin/python
import objc
objc.setVerbose(True)
import os, sys
"""
This should test the interaction between a OSX Quartz call
and twisted.web.
To run, call the twistd binary with this script.
In order to establish that the image generation works, independently of twisted,
this script will generate an image first, and print some results.
Then twisted will start and do its thing.
This starts the process as a daemon, and will cause a crash on 10.6 flagged with
USING_FORK_WITHOUT_EXEC_IS_NOT_SUPPORTED_BY_FILE_MANAGER
/usr/bin/twistd -y twisted.quartz.test.py --pidfile quartztestpid.txt --logfile quartztest.log
When the script is called with the no daemon option:
/usr/bin/twistd -n -y twisted.quartz.test.py --pidfile quartztestpid.txt --logfile quartztest.log
...the server works. Images are generated.
Then talk to the server in a webbrowser:
http:127.0.0.1:8081
e...@letterror.com
"""
import sys
from random import random
from twisted.web import resource, server
from twisted.internet import reactor
from twisted.application import service, internet
import time
def getTestImagePath():
p = os.path.join(os.getcwd(), "LayoutTest1.png")
print os.path.exists(p)
return p
def _makeContext(size):
width, height = size
data = None
bitsPerComponent = 8
numComponents = 4
bestByteAlignment = 16
bytesPerRow = width * (bitsPerComponent / 8) * numComponents
bytesPerRow = ((bytesPerRow + (bestByteAlignment - 1)) & ~(bestByteAlignment - 1))
bitmapInfo = Quartz.kCGImageAlphaPremultipliedLast
data = None
context = Quartz.CGBitmapContextCreate(data, width, height, 8, bytesPerRow, rasterColorSpace, bitmapInfo)
return context
def _drawTestData(context):
steps = 10
size = 10
for x in range(steps):
for y in range(steps):
r, g, b, a = random(), random(), 0, 0.5
color = Quartz.CGColorCreate(rasterColorSpace, (r, g, b, a))
Quartz.CGContextSetFillColorWithColor(context, color)
Quartz.CGContextFillRect(context, Quartz.CGRectMake(x*size, y*size, size, size))
def _drawImage(context):
#path = u"/Users/erik/Develop/lettersetter/trunk/lettersetter/TestData/LayoutTest1.png"
#path = u"http://www.python.org/images/python-logo.gif";
path = getTestImagePath()
print "_drawImage step 1", os.getpid()
url = Quartz.CFURLCreateWithFileSystemPath(None, path, Quartz.kCFURLPOSIXPathStyle, False)
print "_drawImage step 2", url, type(url)
imageSource = Quartz.CGImageSourceCreateWithURL(url, {Quartz.kCGImageSourceTypeIdentifierHint: "png"})
print "_drawImage step 3", imageSource
image = Quartz.CGImageSourceCreateImageAtIndex(imageSource, 0, {})
w = Quartz.CGImageGetWidth(image)
h = Quartz.CGImageGetHeight(image)
x, y = (10,10)
rect = Quartz.CGRectMake(x, y, w, h)
print "_drawImage step 4", x, y, w, h
Quartz.CGContextDrawImage(context, ((x, y), (w, h)), image)
def _makeTestData(context):
data = Quartz.CFDataCreateMutable(None, 0)
dataConsumer = Quartz.CGDataConsumerCreateWithCFData(data)
fileType = "public.png"
imageDestination = Quartz.CGImageDestinationCreateWithDataConsumer(dataConsumer, fileType, 1, None)
image = Quartz.CGBitmapContextCreateImage(context)
properties = {
Quartz.kCGImagePropertyDPIWidth : 72,
Quartz.kCGImagePropertyDPIHeight : 72,
}
Quartz.CGImageDestinationAddImage(imageDestination, image, properties)
Quartz.CGImageDestinationFinalize(imageDestination)
# still a CFMutableData Reference, it needs to be a string
return str(data)
def buildTestImage():
context = _makeContext((100,100))
_drawTestData(context)
_drawImage(context)
return _makeTestData(context)
class RootResource(resource.Resource):
def render(self, request):
resource.Resource.__init__(self)
data = buildTestImage()
_format = "png"
request.setHeader("Content-Type", "image/%s"%_format)
return str(data)
def getChild(self, name, request):
return self
# first make the image to see if it works outside of twisted
def startup():
global Quartz, rasterColorSpace
import Quartz
rasterColorSpace = Quartz.CGColorSpaceCreateWithName(Quartz.kCGColorSpaceGenericRGB)
#data = buildTestImage()
#path = os.path.join(os.getcwd(), "twisted_quartz_test_result.png")
#f = open(path, 'wb')
#f.write(data)
#f.close()
#print "saved test image at", path
# print some version info
import sys
print "python version:", sys.version
print "pyobjc version:", objc.__version__
import twisted.web
print "twisted.web version:", twisted.web.__version__
# if properly booted, this will start a twisted process
port = 8081
site = server.Site(RootResource())
application = service.Application('QuartzTestApp')
sc = service.IServiceCollection(application)
i = internet.TCPServer(port, site)
i.setServiceParent(sc)
reactor.callWhenRunning(startup)
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