agh has asked for the wisdom of the Perl Monks concerning the following question:

Hi all,

I need to start a postgres daemon and redirrect it's STDERR and STDOUT to a logfile rotator (can't mix them). Here's a sketch of what I'm thinking: 

use IPC::Open3;

our $rotatelogs_bin = '';
our $rotate_size = '10M';    # must end with M, see rotatelogs docs
our $logdir = '/home/ahammond/logtest/log';
our $pg_bin = '/home/ahammond/logtest/belcher.pl';
our $pg_args = '';

# start by opening stdout and stderr loggers

open (STDOUTLOG, "| $rotatelogs_bin $logdir/stdout.log $rotate_size")
or die "Can't open stdoutlog: $!\n";

open (STDERRLOG, "| $rotatelogs_bin $logdir/stderr.log $rotate_size")
or die "Can't open stderrlog: $!\n";

# filehandle manipulation here?

our $pid = open3 (\*STDIN, \*STDOUTLOG, \*STDERRLOG,
                  $pg_bin, $pg_args);

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What I'm wondering is about efficiency. Is there a better way to do this? I'd very much like to exec the final call to the postmaster daemon so that I don't have the overhead of a perl instance. Is is possible to detach these processes? Should I be writing this in shell?

Drew

Replies are listed 'Best First'.
Re: efficiently dispatching loggers for daemon
by bageler (Hermit) on Mar 08, 2004 at 23:26 UTC
    make use of the system handles for in/out/err:

    somecommand > stdout.log 2>stderr.log
[reply]
[d/l]

      Thanks for the comment, but this does not address my problem. I can't just dump output to a file. I need to feed it through a log rotator. And I need to keep STDERR and SDTOUT seperate so I can't do something like: 

      exec 2>&1
daemon | rotatelogs &

      [download]

      The daemon in question is Postgres' postmaster driving a pretty hefty database. I can't go restarting it every time I need to rotate a log file and it doesn't re-open log file handles on HUP.

      I'm considering re-dirrecting to named pipes, but I don't want to risk them getting full and blocking the database. Syslog sadly is not an option for political reasons.

      Any suggestions would be greatly appreciated.

[reply]
[d/l]
        what's the difference in your stdout vs stderr? the standard method of starting postgres (using pg_ctl) already combines the outputs...

        I looked around and the only thing ppl have done to solve the problem of keeping them separate is to used named pipes. good luck!
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Re: efficiently dispatching loggers for daemon
by bageler (Hermit) on Mar 23, 2004 at 23:46 UTC
    I was looking at the tcsh manual today and found something that may help!

    Diagnostic output may be directed through a pipe with the standard output. Simply use the form `|&' rather than just `|'.

    and

    The shell cannot presently redirect diagnostic output without also redirecting standard output, but `(command > output-file) >& error-file' is often an acceptable workaround. Either output-file or error-file may be `/dev/tty' to send output to the terminal.

    so it follows that you should be able to do `(command | stdoutlogger) |& errorlogger`
[reply]

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