My PyLucene app freezes when run as a daemon

Fri Mar 23 21:54:00 GMT 2007

Ofer Nave wrote:
> This might be a bit off the usual topic range here, but I was pointed to
> this list.
>> Background:
>> PyLucene is a GCJ-compiled version of Java Lucene integrated with Python.
> http://pylucene.osafoundation.org/
>> Context:
>> I have a PyLucene searcher application running under a multithreaded python
> web server called Paste (http://pythonpaste.org). I've added a command-line
> argument to my script to run the script as a daemon based on the code in
> this article: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/278731
>> Problem:
>> When the script is run as a normal process, it works fine. When it is run
> as a daemon, it freezes after about a dozen requests. The point it's
> freezing at is in a call to a class that is known to not be thread-safe, so
> that might be the problem - but on the other hand, the only difference
> between the good and bad scenarios is whether it's running as a daemon, so I
> tend to lean towards that as my top clue.
>> How I Got Here:
>> I posted this to the PyLucene list, and was told: "You might want to ask
> java@gcc.gnu.org about daemonizing a process using libgcj and boehm-gc." So
> I'm giving it a shot. Does anyone have wisdom on the care and feeding of
> daemonized processes built with GCJ? Is there anything special I need to
> know about?
>> Appendix 1 - My daemonize() Function:
>> # call to detach yourself from a terminal
> def daemonize(logfile=None):
> # fork twice to sever any ties
> _fork()
> os.setsid()
> _fork()
> os.chdir(WORKDIR)
> os.umask(UMASK)
>> # close standard I/O channels
> os.close(0) # stdin
> os.close(1) # stdout
> os.close(2) # stderr
>> # redirect standard output channels to logfile
> if logfile:
> sys.stdout = sys.stderr = logfile
>> # set up SIGTERM handler for cleanup
> signal(SIGTERM, _sigterm_handler)
>> -ofer
>
It would not surprise me if that caused problems. Does it work with 
Sun's runtime?
If you want to daemonize, I would recommend doing it in C code before 
calling JvRunMain. I am also unsure what happens if you close stdout 
and stderr. I would hope that you don't do anything that would cause 
libgcj to try to write to those descriptors. It might help to open 
stdout and stderr to /dev/null
Other that that I would recommend attaching gdb to it to see where it is 
stuck.
David Daney