[ python-Bugs-932563 ] logging: need a way to discard Logger objects

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Bugs item #932563, was opened at 2004-04-09 17:51
Message generated for change (Comment added) made by fdrake
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Category: Python Library
Group: Feature Request
Status: Open
Resolution: None
Priority: 5
Submitted By: Fred L. Drake, Jr. (fdrake)
>Assigned to: Vinay Sajip (vsajip)
Summary: logging: need a way to discard Logger objects

Initial Comment:
There needs to be a way to tell the logging package
that an application is done with a particular logger
object.  This is important for long-running processes
that want to use a logger to represent a related set of
activities over a relatively short period of time
(compared to the life of the process).

This is useful to allow creating per-connection loggers
for internet servers, for example.  Using a
connection-specific logger allows the application to
provide an identifier for the session that can be
automatically included in the logs without having the
application encode it into each message (a far more
error prone approach).


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>Comment By: Fred L. Drake, Jr. (fdrake)
Date: 2004-06-24 00:13

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Looking at this again, after adjusting the application I
have that used the connection-specific loggers, I decided
that a different approach better solves the problem.

What you've shown requires exactly what I wanted to avoid:
having to make a gesture at each logging call (to transform
the message).  Instead of doing this, I ended up writing a
wrapper for the logger objects that implement the methods
log(), debug(), info(), warn(), warning(), error(),
exception(), critical(), and fatal().  These methods each
transform the message before calling the underlying logger.

It would be really nice to have something like this that
isolates the final call to Logger._log() so specific
implementations can simply override _log() (or some other
helper routine that gets all the info) and maybe the
__init__().  I don't think that's completely necessary, but
would probably make it a lot easier to implement this pattern.

There's probably some useful documentation improvements that
could be made to help people avoid the issue of leaking loggers.

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Comment By: Fred L. Drake, Jr. (fdrake)
Date: 2004-06-10 12:50

Message:
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Sorry for the delay in following up.

I'll re-visit the software where I wanted this to see how
it'll work out in practice.

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Comment By: Tim Peters (tim_one)
Date: 2004-06-09 12:01

Message:
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Assigned to Fred, because Vinay wants his input (in general, 
a bug should be assigned to the next person who needs 
to "do something" about it, and that can change over time).

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Comment By: Vinay Sajip (vsajip)
Date: 2004-06-09 05:28

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Fred, any more thoughts on this? Thanks, Vinay

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Comment By: Vinay Sajip (vsajip)
Date: 2004-05-08 15:28

Message:
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The problem with disposing of Logger objects 
programmatically is that you don't know who is referencing 
them. How about the following approach? I'm making no 
assumptions about the actual connection classes used; if you 
need to make it even less error prone, you can create 
delegating methods in the server class which do the 
appropriate wrapping.

class ConnectionWrapper:
	def __init__(self, conn):
		self.conn = conn
		
	def message(self, msg):
		return "[connection: %s]: %s" % 
(self.conn, msg)
		
		
and then use this like so...

class Server:

	def get_connection(self, request):
		# return the connection for this request
		
	def handle_request(self, request):
		conn = self.get_connection(request)
		# we use a cache of connection wrappers
		if conn in self.conn_cache:
			cw = self.conn_cache[conn]
		else:
			cw = ConnectionWrapper(conn)
			self.conn_cache[conn] = cw
		#process request, and if events need to 
be logged, you can e.g.
		logger.debug(cw.message("Network packet 
truncated at %d bytes"), n)
		#The logged message will contain the 
connection ID


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