More and more, we're eliminating Linux boxes in favor of Solaris. This is generally not a huge deal, but one of the niggling details has been Sun's cron. It sucks. It sucks because it uses a constant as the subject of its alert messages. If you have a lot of servers running a lot of cron jobs, generating a lot of output, you end up with a display that looks like this:
1 N Oct17 Super-User ( 7) Output from "cron" command 2 N Oct17 Super-User ( 7) Output from "cron" command 3 N Oct17 Super-User ( 7) Output from "cron" command 4 N Oct17 Super-User ( 7) Output from "cron" command 5 N Oct18 Super-User ( 7) Output from "cron" command 6 N Oct18 Super-User ( 7) Output from "cron" command 7 N Oct18 Super-User ( 7) Output from "cron" command 8 N Oct18 Super-User ( 7) Output from "cron" command 9 N Oct18 Super-User ( 7) Output from "cron" command 10 N Oct18 Super-User ( 7) Output from "cron" command 11 N Oct18 Super-User ( 7) Output from "cron" command
Seriously?
So, I put in a change request to have this fixed. Deploying Vixie cron was going to be a massive pain (I was told) so instead we updated our use of puppet to ensure that our cronjobs were run by a wrapper script. I'm really happy with it, as it eliminates a few other crappy wrapper scripts and gets me what I wanted to begin with. There are a few internal modules used below, but it should be trivial to replace them with whatever you want. (I've removed a few constants, too.)
Maybe I'll CPANize this later.
#!/usr/bin/perl
use strict;
use warnings;
use Digest::MD5 qw(md5_hex);
use Fcntl qw(:flock);
use Getopt::Long::Descriptive;
use ICG::SvcLogger;
use IPC::Run3 qw(run3);
use String::Flogger qw(flog);
use Sys::Hostname::Long;
use Text::Template;
use Time::HiRes ();
my ($opt, $usage) = describe_options(
'%c %o',
[ 'command|c=s', 'command to run (passed to ``)', { required => 1 } ],
[ 'subject|s=s', 'subject of mail to send (defaults to command)' ],
[ 'rcpt|r=s@', 'recipient of mail; may be given many times', ],
[ 'errors-only|E', 'do not mail if exit code 0, even with output', ],
[ 'sender|f=s', 'sender for message', ],
[ 'jobname|j=s', 'job name; used for locking, if given' ],
[ 'lock!', 'lock this job (default: lock; --no-lock to not)',
{ default => 1 } ],
);
die "illegal job name: $opt->{jobname}\n"
if $opt->{jobname} and $opt->{jobname} !~ m{\A[-a-z0-9]+\z};
my $rcpts = $opt->{rcpt}
|| [ split /\s*,\s*/, ($ENV{MAILTO} ? $ENV{MAILTO} : '...') ];
my $host = hostname_long;
my $sender = $opt->{sender} || sprintf '%s@%s', ($ENV{USER}||'cron'), $host;
my $subject = $opt->{subject} || $opt->{command};
$subject =~ s{\A/\S+/([^/]+)(\s|$)}{$1$2} if $subject eq $opt->{command};
my $logger = ICG::SvcLogger->new({
program_name => 'cronjob',
facility => 'cron',
});
my $lockfile = sprintf '.../cronjob.%s', $opt->{jobname} || md5_hex($subject);
goto LOCKED if ! $opt->{lock};
open my $lock_fh, '>', $lockfile or die "couldn't open lockfile $lockfile: $!";
flock $lock_fh, LOCK_EX | LOCK_NB or die "couldn't lock lockfile $lockfile";
printf $lock_fh "running %s\nstarted at %s\n",
$opt->{command}, scalar localtime $^T;
LOCKED:
$logger->log([ 'trying to run %s', $opt->{command} ]);
my $start = Time::HiRes::time;
my $output;
$logger->log_fatal([ 'run3 failed to run command: %s', $@ ])
unless eval { run3($opt->{command}, \undef, \$output, \$output); 1; };
my %waitpid = (
status => $?,
exit => $? >> 8,
signal => $? & 127,
core => $? & 128,
);
my $end = Time::HiRes::time;
unlink $lockfile if -e $lockfile;
my $send_mail = ($waitpid{status} != 0)
|| (length $output && ! $opt->{errors_only});
if ($send_mail) {
require Email::Simple;
require Email::Simple::Creator;
require ICG::Sendmail;
require Text::Template;
my $template = do { local $/; };
my $body = Text::Template->fill_this_in(
$template,
HASH => {
command => \$opt->{command},
output => \$output,
time => \(sprintf '%0.4f', $end - $start),
waitpid => \%waitpid,
},
);
my $subject = sprintf '%s%s',
$waitpid{status} ? 'FAIL: ' : '',
$subject;
my $email = Email::Simple->create(
body => $body,
header => [
To => join(', ', @$rcpts),
From => qq{"cron/$host" <$sender>},
Subject => $subject,
],
);
ICG::Sendmail->sendmail(
$email,
{
to => $rcpts,
from => $sender,
archive => undef,
}
);
}
__DATA__
Command: { $command }
Time : { $time }s
Status : { join('', flog('%s', \%waitpid)) }
Output :
{ $output || '(no output)' }
Re:Superfluous $2?
rjbs on 2008-10-18T18:05:14
I think it is needed. If the input is "/foo/bar baz" then $2 is whitespace. Dropping it would make the subject "barbaz" instead of "bar baz"
I have not tested this, but it was my intent and seems correct.
Re:Superfluous $2?
kraai on 2008-10-18T18:18:56
Ah, I see. Thanks for the explanation.