A runner script to run any command and save its stdout and stderr in a timestamped log file, ready to be harvested by Logstash. Adds JSON metadata, and optionally locks the command, ensuring it doesn't run in multiple copies at the same time.

runner.pl

#!/usr/bin/env perl -w
#
#            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
#                    Version 2, December 2004
#
# Copyright (C) 2013 Maciej Pasternacki <maciej@pasternacki.net>
#
# Everyone is permitted to copy and distribute verbatim or modified
# copies of this license document, and changing it is allowed as long
# as the name is changed.
#
#            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
#   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
#
#  0. You just DO WHAT THE FUCK YOU WANT TO.

use strict;

use Cwd;
use Fcntl qw(:flock);
use File::Basename;
use File::Spec;
use Getopt::Long;
use IO::Select;
use IPC::Open3;
use Time::HiRes;
use Time::Piece;
use JSON;

our $pid = 0;
our $exited = 0;
our $lock = 0;
our $timeout;
our $name;
our $basedir;
our $command;
our $chdir;

sub say {
  my ( $tag, $message, %meta ) = @_;
  my ( $sec, $usec ) = Time::HiRes::gettimeofday;
  my $line = sprintf "%s.%.06dZ %s[%d] %s %s",
    Time::Piece->gmtime($sec)->datetime, $usec,
        $name, $pid, uc($tag),
          $message;
  $line .= " ".encode_json(\%meta) if %meta;
  print LOGFILE "$line\n";
}

sub handle {
  foreach my $fh ( @_ ) {
    my $tag = ( $fh == \*CHILD_OUT ? 'stdout' :
                  $fh == \*CHILD_ERR ? 'stderr' :
                    'wtf' );
    while ( <$fh> ) {
      chomp;
      /^$/ and next;
      say $tag, $_;
    }
  }
}

my ( $_help, $_debug );
if ( !GetOptions( 'timeout=i' => \$timeout,
                  'name=s' => \$name,
                  'dir=s' => \$basedir,
                  'chdir=s' => \$chdir,
                  'lock' => \$lock,
                  'debug' => \$_debug,
                  'help' => \$_help )
       || $_help
       || $#ARGV < 0) {
  print <<END;
USAGE: $0 [OPTIONS] -- command to run ...
OPTIONS:
  --timeout,-t SECONDS
  --name,-n NAME Name of process (default: basename of given command)
  --dir,-d DIR   Base directory to write files to (default: current dir)
  --chdir,-c DIR Change directory before running command
  --lock,-l      Don't allow running multiple instances of process at the same time
  --debug        Print log to stderr instead of file
END
  exit !$_help;
}

chdir $chdir if defined $chdir;

$name ||= basename($ARGV[0]);
$basedir ||= getcwd;
$command = join(' ', @ARGV);

open LOGFILE, $_debug ? ">&STDERR" : ">>".File::Spec->catfile($basedir, $name).".log";

unless ( flock(LOGFILE, ($lock ? LOCK_EX : LOCK_SH)|LOCK_NB) ) {
  say 'locked', "Can't obtain lock", reason => $!;
  exit -1;
}

$SIG{CHLD} = sub {
  say 'sigchld', $command if $_debug;
  $exited = 1;
};

$pid = open3('<&0', \*CHILD_OUT, \*CHILD_ERR, @ARGV);
say 'start', $command, lock => $lock, timeout => $timeout, cwd => getcwd;

if ( defined $timeout ) {
  $SIG{ALRM} = sub {
    say 'timeout', $command;
    # TODO: graceful kill?
    kill 'TERM', $pid;
  };
  alarm $timeout;
}

our $sel = IO::Select->new(\*CHILD_OUT, \*CHILD_ERR);
while ( my @ready = $sel->can_read(0.1) ) {
  handle @ready;
  last if $exited;
}
handle(\*CHILD_OUT, \*CHILD_ERR);

waitpid $pid, 0;
my ($rv, $sig) = ($?>>8, $?&127);

my %meta;
$meta{status} = $rv;
$meta{signal} = $sig if $sig;

say 'finished', $command, %meta;

exit ($rv || ($sig?-1:0));