Re: [log4perl-devel] open files when running init_and_watch

[Mike S. <m...@pe...>]

On Mon, 6 Mar 2006, Martin J. Evans wrote:

> I thought calling get_logger would actually open the file
> and init_and_watch would simply parse the conf file, check it
> was OK and watch the conf file.
>
> If I'd called get_logger(x::y::z) then I could understand
> the log file associated with x::y::z and x::y being opened
> but If I call get_logger(x::y) then why would the log
> file associated with x::y::z be opened.

Loggers and appenders are orthogonal concepts in Log4perl. If you get
a logger, nothing happens with the appender. Only when the logger decides
to fire, the appender comes into play (according to the configuration).

The standard Log::Log4perl::Appender::File appender in Log4perl opens
its files at init() because it's usually not a problem having a handful
of files open, even if they're not written to. Alternatively, it could
open the files at log() time, which would impose a small penalty on
the appenders with every log().

> > I wonder how it is possible to run out of file descriptors with only
> > three open files per process, though. Are you running hundreds of
> > daemons simultaneously?
>
> Perhaps I should have been clearer. I am running out of file descriptors
> (but within a single process, not system wide) and it was that
> which prompted me to look at what files I've got open. By the
> time you add a file descriptor for the perl binary and every module
> you've "use"ed, then every shared object you need it amounts to quite a
> bit (easily more than 64).

64 file descriptors per process sounds really low. On my linux box at home it
is

    $ ulimit -n
    1024

> I don't want files created and opened which I'm not going to log to.
> In my mind if I've not called get_logger("x::y") then I'm
> not going to log to the file that is defined by x::y (unless I've
> called get_logger(x::y::z). I will look
> at Appender but it seems to get ONLY the files opened which I'm
> actually going to use in the current process I need a separate
> conf file for each process which only defines the appenders
> I intend using this time around. If that is the way it is
> - fair enough - I can live with that.

If you really need to save those 3 file descriptors, I'd recommend writing
your own file appender that opens the file at log() time, on demand. It's really
a 20-liner.

-- Mike

Mike Schilli
m...@pe...

> As I said, perhaps I've misunderstood appenders and the conf file
> but I'm "currently" at a loss to understand why a file is created
> and opened when there is no likelihood of anything being written
> to it. Perhaps you could put me right on any misunderstanding
> I have.
>
> Martin
>
> >>This may
> >>be my misunderstanding of the way log4perl works but it is
> >>undesirable for me so I wondered if either a) these log files should
> >>not be open or b) if my conf file was wrong. Given:
> >>
> >>log4perl.logger.Server = WARN
> >>log4perl.logger.Server.Markets.Close = DEBUG, A1
> >>log4perl.appender.A1=Log::Dispatch::File
> >>log4perl.appender.A1.filename=/tmp/markets_close.log
> >>log4perl.appender.A1.mode=append
> >>log4perl.appender.A1.layout=Log::Log4perl::Layout::PatternLayout
> >>log4perl.appender.A1.layout.ConversionPattern=%d %p> %F{1}:%L %M - %m%n
> >>log4perl.appender.A1.Threshold=INFO
> >>
> >>log4perl.logger.Server.CGI.Post = DEBUG, A3
> >>log4perl.appender.A3=Log::Dispatch::File
> >>log4perl.appender.A3.filename=/tmp/cgi_post.log
> >>log4perl.appender.A3.mode=append
> >>log4perl.appender.A3.layout=Log::Log4perl::Layout::PatternLayout
> >>log4perl.appender.A3.layout.ConversionPattern=%d %p> %F{1}:%L %M - %m%n
> >>
> >>log4perl.logger.Server.Queued = DEBUG, A5
> >>log4perl.appender.A5=Log::Dispatch::File
> >>log4perl.appender.A5.filename=/tmp/queued.log
> >>log4perl.appender.A5.mode=append
> >>log4perl.appender.A5.layout=Log::Log4perl::Layout::PatternLayout
> >>log4perl.appender.A5.layout.ConversionPattern=%d %p> %F{1}:%L %M - %m%n
> >>
> >>why are A1.filename, A3.filename and A5.filename all created and open when I
> >>run the above Perl. I would have expected A5.filename to be opened when I did
> >>get_logger("Server::Queued") but no files other than log4.conf to be open when
> >>all I've done is init_and_watch.
> >>
> >>Any ideas.
> >>
> >>Martin
>
>
>
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