cgi "print statement" in multithreaded enviroment?

vegetax · May 3, 2005

How can i use cgi'like print statement in a multitreaded web framework?
each thread has its own Servlet instance with request/response objects,
sys.stdout = self.response(which is a file like object) wont work because
all threads will set the same file object and it will be a concurrence
mess.

I am out of ideas here,so any hacks welcome =)

Irmen de Jong · May 3, 2005

vegetax said:
How can i use cgi'like print statement in a multitreaded web framework?
each thread has its own Servlet instance with request/response objects,
sys.stdout = self.response(which is a file like object) wont work because
all threads will set the same file object and it will be a concurrence
mess.

I am out of ideas here,so any hacks welcome =)

instead of:

print "<html>.....</html>

do:

print >>self.response, "<html>....</html>"

--Irmen

vegetax · May 3, 2005

Irmen said:
instead of:

print "<html>.....</html>

do:

print >>self.response, "<html>....</html>"

--Irmen

But i want to use "print" as a commodity feature, print >>
self.response,'html..' is longer to type than
self.response.write('html..')

The only clear way i am thinking right now is to write a preprocessor ,like
quixote ptl,but thats sloww

Paul Rubin · May 3, 2005

vegetax said:
But i want to use "print" as a commodity feature, print >>
self.response,'html..' is longer to type than
self.response.write('html..')

w = self.response.write

w('html...')
w('more html...')
w('still more html')

Bengt Richter · May 3, 2005

But i want to use "print" as a commodity feature, print >>
self.response,'html..' is longer to type than
self.response.write('html..')

The only clear way i am thinking right now is to write a preprocessor ,like
quixote ptl,but thats sloww

Maybe assign an object to sys.stdout that has write etc methods that check
what thread is calling and use self.response things that you assign to
a property of that sys.stdout object instead of directly to sys.stdout.

I.e., something like

sys.stdout = my_stdout_dispatcher
...
# property out_channels stores self.response with thread id:
sys.stdout.out_channels = self.response(which is a file like object)
...

# print => sys.stdout.write => my_stdout_dispatcher.write('from some thread')
# which atomically looks up right self.response
print 'from some thread'

You may need some lock stuff to do this properly
(to make self.response lookup info access effectively atomic),
but that's a general idea. I don't know what other thread interaction issues
you may have with the state of possibly mutable data being printed.

This is just an idea for an approach. I may not be understanding your problem at all ;-)

Regards,
Bengt Richter

vegetax · May 3, 2005

Bengt said:
Maybe assign an object to sys.stdout that has write etc methods that check
what thread is calling and use self.response things that you assign to
a property of that sys.stdout object instead of directly to sys.stdout.

I.e., something like

sys.stdout = my_stdout_dispatcher
...
# property out_channels stores self.response with thread id:
sys.stdout.out_channels = self.response(which is a file like object)
...

# print => sys.stdout.write => my_stdout_dispatcher.write('from some
# thread') which atomically looks up right self.response
print 'from some thread'

You may need some lock stuff to do this properly
(to make self.response lookup info access effectively atomic),
but that's a general idea. I don't know what other thread interaction
issues you may have with the state of possibly mutable data being printed.

This is just an idea for an approach. I may not be understanding your
problem at all ;-)

Regards,
Bengt Richter

Something like this:

class ThreadSpecificFile:
         def __init__(s):
             self.files = []
         def set_stdout(f,thread_id):
             self.files[thread_id] = f
         def clean_up(thread_id):
             del self.files[thread_id]
         def write(data):
             self.files[thread.get_ident()].write(data)

sys.stdout = ThreadSpecificFile()

Should be a lock for self.files and i am not sure how to make
thread.get_ident() atomic

What is the problem with writing singleton in multithreaded enviroment	3	Jan 14, 2007
print in multithreaded environement ???	4	Feb 25, 2004
PyWart: The problem with "print"	102	Jun 2, 2013
print header for output	0	Jun 19, 2011
Errin when executing a cgi script that sets a cookie in the browser	32	Jun 5, 2013
Multithreaded COM server problem...	10	Jan 10, 2004
CGI, POST, and file uploads	0	Mar 3, 2010
Multithreaded Sleeping in a single Instance	4	Mar 29, 2006

cgi "print statement" in multithreaded enviroment?

vegetax

Irmen de Jong

vegetax

Paul Rubin

Bengt Richter

vegetax

Ask a Question

Similar Threads

Members online

Forum statistics

Latest Threads