Logging module gives duplicate log entries

[Shiao]

Hi,
I am getting duplicate log entries with the logging module.

The following behaves as expected, leading to one log entry for each
logged event:

logging.basicCo nfig(level=logg ing.DEBUG, filename='/tmp/foo.log')

But this results in two entries for each logged event:

applog = logging.getLogg er()
applog.setLevel (logging.DEBUG)
hdl = logging.FileHan dler('/tmp/foo.log')
applog.addHandl er(hdl)
The app is based on the web.py framework, so I guess my problem may
be
connected to be some interaction with other uses of logging within
the
framework. This is not specific to the root logger, the same happens
with logging.getLogg er('foo').

Any clue would be more than welcome.

best,
ShiaoBu

[Amit Khemka]

On 8/21/07, Shiao <mu*******@gmai l.comwrote:

Hi,
I am getting duplicate log entries with the logging module.

The following behaves as expected, leading to one log entry for each
logged event:

logging.basicCo nfig(level=logg ing.DEBUG, filename='/tmp/foo.log')

But this results in two entries for each logged event:

applog = logging.getLogg er()
applog.setLevel (logging.DEBUG)
hdl = logging.FileHan dler('/tmp/foo.log')
applog.addHandl er(hdl)

You need to remove the handler from the logging object

# remove the handler once you are done
applog.removeHa ndler(hdl)
Cheers,
amit.

----
Amit Khemka
website: www.onyomo.com
wap-site: www.owap.in
Home Page: www.cse.iitd.ernet.in/~csd00377

Endless the world's turn, endless the sun's Spinning, Endless the quest;
I turn again, back to my own beginning, And here, find rest.

[Shiao]

>
You need to remove the handler from the logging object

# remove the handler once you are done
applog.removeHa ndler(hdl)

Cheers,
amit.

I'm not sure how this could help.

[Peter Otten]

Shiao wrote:

>You need to remove the handler from the logging object

# remove the handler once you are done
applog.removeH andler(hdl)

I'm not sure how this could help.

If you have multiple handlers you'll get a logged message for every handler.

In your code logging.basicCo nfig() implicitly adds a handler and you add
another one calling addHandler(). Let's use a StreamHandler to see the
effect immediately:

>>import logging
logging.basic Config()
root = logging.getLogg er()
root.warn("on ce")

WARNING:root:on ce

>>handler = logging.StreamH andler()
root.addHandl er(handler)
root.warn("tw ice")

WARNING:root:tw ice
twice

>>root.removeHa ndler(handler)
root.warn("on ce again")

WARNING:root:on ce again

Of course it would be preferable not to add a second handler in the first
place, either by omitting the basicConfig() or the explicit addHandler()
call.

Peter

[Shiao]

Maybe my question wasn't very clear. What I meant is that these four
lines lead in my case to two entries per logged event:

applog = logging.getLogg er()
applog.setLevel (logging.DEBUG)
hdl = logging.FileHan dler('/tmp/foo.log')
applog.addHandl er(hdl)

However if I REPLACE the above by:

logging.basicCo nfig(level=logg ing.DEBUG, filename='/tmp/foo.log')

things work as expected.

[Peter Otten]

Shiao wrote:

Maybe my question wasn't very clear. What I meant is that these four
lines lead in my case to two entries per logged event:

applog = logging.getLogg er()
applog.setLevel (logging.DEBUG)
hdl = logging.FileHan dler('/tmp/foo.log')
applog.addHandl er(hdl)

However if I REPLACE the above by:

logging.basicCo nfig(level=logg ing.DEBUG, filename='/tmp/foo.log')

things work as expected.

Then you have a logic error in your program that causes that piece of code
to run twice (I simulate that by the for-loop):

$ python
Python 2.5.1 (r251:54863, May 2 2007, 16:56:35)
[GCC 4.1.2 (Ubuntu 4.1.2-0ubuntu4)] on linux2
Type "help", "copyright" , "credits" or "license" for more information.

>>import logging
for i in range(2):

.... logging.getLogg er().addHandler (logging.Stream Handler())
....

>>logging.warn( "twice")

twice
twice

logging.basicCo nfig() on the other hand does nothing if it finds existing
handlers:

$ python
Python 2.5.1 (r251:54863, May 2 2007, 16:56:35)
[GCC 4.1.2 (Ubuntu 4.1.2-0ubuntu4)] on linux2
Type "help", "copyright" , "credits" or "license" for more information.

>>import logging
for i in range(2):

.... logging.basicCo nfig()
....

>>logging.warn( "once")

WARNING:root:on ce

Peter