On 2007-04-04, Andrey Semashev <andysem@mail.ru> wrote:
I see. I guess now I'm beginning to understand what channels are meant for. The channel appears to be yet another attribute which defines the "class" of the log record (i.e. an access log, debug trace, etc.).
I think channels are often thought of as a routing mechanism for log messages. The message is passed to a channel which is connected to filters, sinks, etc. The notion is, I believe, isomorphic to some systems of tagging (in conjunction, again, with filters) that have been mentioned. So yes, it's just another attribute that used to determine how/where the message is formatted, written, and so forth.
Seems to me we have to fix the set of mandatory attributes that every log record should always have and leave space for optional attributes (channels go here). I see these attributes as mandatory: - record number (increments for each record collected) - record date and time - thread name (if not set - thread id) - scope stack - severity level - message text
I think that defining a mandatory set of attributes is going to rub a lot of users (me included) the wrong way. My sense is that we will be better served by a system that let's you dynamically (and easily!) associate attributes with a message. Moreover, it needs to be simple to do that on a global or per entity (e.g. channel, sink, message) basis. We could provide the kinds of formatters you describe with the library as they have obvious general utility. My main point, though, is that no mandated set of attributes will please everyone and may well be a huge point of contention.
As for optional attributes I think, it's better to leave them on user's behalf since it's too difficult to figure out the correct set of them and implement suitable interface to operate them in the unified and convenient way. But, surely, the library should leave an easy way to implement them.
I agree with this completely, except that (per above) it should apply to all attributes :) -- Austin Bingham Signal & Information Sciences Laboratory Applied Research Laboratories, University of Texas at Austin 10000 Burnet Rd., Austin, TX 78758 email: abingham@arlut.utexas.edu