daemon.DaemonContext
Rebelo
when i have logging and using daemon.DaemonContext()
i tried passing :
fh = logging.handlers.TimedRotatingFileHandler(LOG_FILENAME, 'midnight',
encoding='utf-8')
with :
context = daemon.DaemonContext()
context.files_preserve=[fh]
but no good
what am i doing wrong?
Rebelo
context = daemon.DaemonContext(stdin=sys.stdin, stdout=sys.stdout,
files_preserve=[fh], signal_map = {signal.SIGTERM:
'terminate',signal.SIGHUP: 'terminate'})
i don't get error but i still can't write to log file
Vinay Sajip
Not sure, offhand.
Change to a script which just writes to the file (rather than going
via logging) - does that work? What platform are you on, what version
etc?
It's unlikely to be a logging-related problem: more likely it's to do
with file descriptors.
Regards,
Vinay Sajip
Vinay Sajip
My guess is - files_preserve needs to be passed a file handle and not
a logging handler.
Regards,
Vinay Sajip
Rebelo
thnx for help.
writing to a file works, but i need logging.
do you know where can i find good documnetation for python-daemon?
Vinay Sajip
No,
but see this post:
http://groups.google.com/group/comp.lang.python/msg/851ce78e53812ade
It may lead you to more information. The thread shows that Sean
DiZazzo got logging working with the package.
I think you just have to pass the file object used by the handler
(fh.stream) in the files_preserve array.
Regards,
Vinay Sajip
Rebelo
i wrote a function in which i start logging after deamon starts
Rebelo
Ben Finney
> On Apr 8, 1:58 pm, Rebelo <puntabl...@gmail.com> wrote:
> > Vinay Sajip wrote:
> > > My guess is - files_preserve needs to be passed a file handle and
> > > not alogginghandler.
This is correct. As the ‘DaemonContext.__init__’ docstring says::
| `files_preserve`
| :Default: ``None``
|
| List of files that should *not* be closed when starting the
| daemon. If ``None``, all open file descriptors will be closed.
|
| Elements of the list are file descriptors (as returned by a file
| object's `fileno()` method) or Python `file` objects. Each
| specifies a file that is not to be closed during daemon start.
> > do you know where can i find good documnetation for python-daemon?
The docstrings and PEP 3143 are currently the best documentation for
‘python-daemon’; both describe the ‘files_preserve’ option as above.
> http://groups.google.com/group/comp.lang.python/msg/851ce78e53812ade
As expressed in the referenced message, I would welcome someone writing
better documentation and contributing patches.
> It may lead you to more information. The thread shows that Sean
> DiZazzo got logging working with the package.
It's important to note (as you did, thanks Vinay) that none of the
‘logging.handlers’ are file descriptors. Nor are they file objects.
If we can get a Python ‘file’ object, we can use its ‘fileno()’ method
to get the file descriptor.
So how do we get the file object for a logging handler? The ‘logging’
module documentation doesn't mention any way to get at the stream object
for the handlers.
But looking at the source code for ‘StreamHandler’ on my system,
‘/usr/lib/python2.5/logging/__init__.py’, shows a ‘stream’ attribute
that is bound to the stream object. It's not marked private (i.e. it's
not named with a leading underscore), so one presumes it is part of the
public API.
> I think you just have to pass the file object used by the handler
> (fh.stream) in the files_preserve array.
Not quite. As the docs specify, you need to pass the *file descriptors*
for the files you want preserved. For regular Python file objects, the
‘file.fileno()’ method returns the file descriptor:
lh = logging.handlers.TimedRotatingFileHandler(
LOG_FILENAME,
# …
)
log_stream_descriptor = lh.stream.fileno()
daemon_context.files_preserve = [log_stream_descriptor]
--
\ “Only the educated are free.” —Epictetus, _Discourses_ |
`\ |
_o__) |
Ben Finney
Ben Finney
> i found a crude workaround:
> i wrote a function in which i start logging after deamon starts
That seems rather sub-optimal; you'll be unable to use the logger for
anything before the daemon context opens. This kind of problem is
exactly what ‘DaemonContext.files_preserve’ is intended to address.
Hopefully you can make use of the ‘DaemonContext.files_preserve’ option
as intended; please see my message earlier in this thread.
--
\ “Of all classes the rich are the most noticed and the least |
`\ studied.” —John Kenneth Galbraith, _The Age of Uncertainty_, |
_o__) 1977 |
Ben Finney
Rebelo
thank you both for a detailed explanation.
Vinay Sajip
> > I think you just have to pass the file object used by the handler
> > (fh.stream) in the files_preserve array.
>
> Not quite. As the docs specify, you need to pass the *file descriptors*
> for the files you want preserved.
Okay, but the docstring you quoted:
"Elements of the list are file descriptors (as returned by a file
object's `fileno()` method) or Python `file` objects."
implies that fh.stream would work as well as fh.stream.fileno(), and I
presume you internally do a hasattr(thingy, 'fileno') to get the
descriptor.
Regards,
Vinay Sajip
Ben Finney
> On Apr 9, 12:46 am, Ben Finney <ben+pyt...@benfinney.id.au> wrote:
> > Not quite. As the docs specify, you need to pass the *file
> > descriptors* for the files you want preserved.
>
> Okay, but the docstring you quoted:
>
> "Elements of the list are file descriptors (as returned by a file
> object's `fileno()` method) or Python `file` objects."
>
> implies that fh.stream would work as well as fh.stream.fileno()
You're quite right, I made a mistake in what I wrote above.
Rebelo <punta...@gmail.com> writes:
> Ben Finney wrote:
> > So how do we get the file object for a logging handler? The
> > ‘logging’ module documentation doesn't mention any way to get at the
> > stream object for the handlers.
> >
> > But looking at the source code for ‘StreamHandler’ on my system,
> > ‘/usr/lib/python2.5/logging/__init__.py’, shows a ‘stream’ attribute
> > that is bound to the stream object. It's not marked private (i.e.
> > it's not named with a leading underscore), so one presumes it is
> > part of the public API.
[…]
> >
> > lh = logging.handlers.TimedRotatingFileHandler(
> > LOG_FILENAME,
> > # …
> > )
> > log_stream_descriptor = lh.stream.fileno()
> >
> > daemon_context.files_preserve = [log_stream_descriptor]
> >
The above can then be simplified as:
lh = logging.handlers.TimedRotatingFileHandler(
LOG_FILENAME,
# …
)
daemon_context.files_preserve = [lh.stream]
> thank you both for a detailed explanation.
I hope this helps you to make better use of ‘python-daemon’, and thank
you for raising questions here.
This is a good addition for the Frequently Asked Questions document; I
will do this and it will be available in the next version of the
library.
--
\ “I prayed for twenty years but received no answer until I |
`\ prayed with my legs.” —Frederick Douglass, escaped slave |
_o__) |
Ben Finney
wo...@4amlunch.net
wo...@4amlunch.net
> I know it's 4 years later, but I'm currently battling this myself. I do exactly this and yet it doesn't appear to be keeping the filehandler open. Nothing ever gets written to logs after I daemonize!
I changed:
context = daemon.DaemonContext(
# Stuff here
)
context.files_preserve[fh.stream]
to:
context = daemon.DaemonContext(
# Stuff here
files_preserve[fh.stream]
)
And now it works.
Ethan Furman
> I know it's 4 years later, but I'm currently battling this myself. I do exactly this and yet it doesn't appear to be keeping the filehandler open. Nothing ever gets written to logs after I daemonize!
correct list?
--
~Ethan~