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Date:      Wed, 10 Jan 2001 10:09:16 +0200
From:      Neil Blakey-Milner <nbm@mithrandr.moria.org>
To:        Greg Black <gjb@gbch.net>
Cc:        Doug Barton <DougB@FreeBSD.org>, Gerhard Sittig <Gerhard.Sittig@gmx.net>, freebsd-hackers@FreeBSD.org
Subject:   Re: how to test out cron.c changes? (was: cvs commit: src/etc crontab)
Message-ID:  <20010110100915.A90618@mithrandr.moria.org>
In-Reply-To: <nospam-3a5b95e412011c9@maxim.gbch.net>; from gjb@gbch.net on Wed, Jan 10, 2001 at 08:51:16AM %2B1000
References:  <20001120193326.C27042@speedy.gsinet> <20001205225656.Z27042@speedy.gsinet> <20001220211548.T253@speedy.gsinet> <3A513799.75EAB470@FreeBSD.org> <20010102133239.V253@speedy.gsinet> <20010107170840.G253@speedy.gsinet> <3A5AE490.D251F590@gorean.org> <20010109124044.A16276@mithrandr.moria.org> <3A5B5656.E2AAF0B5@FreeBSD.org> <nospam-3a5b95e412011c9@maxim.gbch.net>

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On Wed 2001-01-10 (08:51), Greg Black wrote:
> If any change to expected cron behaviour is to be introduced,
> the traditional behaviour must be the default, with a knob
> documented in the man pages that can be twisted to get the
> oddball behaviour that is being proposed here.

The oddball behaviour that is what, I imagine, the vast majority of
people expect.  We could take a vote here, if you like.  Are you at all
deluded into believing your position would win?

I'm sorry, but cron should never miss jobs.  And it should preferably
not run the same job twice.  All the hacks we've had to go through to
simply get our daily jobs to run reliably (yes, this "reliable" word
again).  This oddball behaviour, unlike the numerous hacks tried before,
and which still don't solve the intrinsic problem, has been tested, and
is default, on OpenBSD, for the past 3 years.

My reading of the code seems to indicate it does the right thing in all
time update cases - it doesn't repeat wildcard jobs multiple times for
the "medium" jump (1 to 3 hours), it doesn't miss jobs for any size jump
forward, and it doesn't repeat jobs for negative jumps.  It just ignores
insanely big jumps (ie, over 3 hours).

Since this is the default in OpenBSD, and we want to not randomly
diverge from their code, and since they're more likely to accept code to
ignore DST changes that a couple of people thinks is the correct thing,
and so forth, we should have the behaviour as default.

(Not to mention that it'll solve the endless complaints about missed or
repeated runs we get twice every year.  And no, these aren't clueless
administrators as you and Doug believe, but people who expect tools to
be reliable and do the obvious thing.  Also, the only reason cron is
doing the wrong thing now is that it is trying to be clever to let
people set jobs in their local time, and we get bit because of silly
things like DST.  It should, of course, be expressed as UTC.)

Neil
-- 
Neil Blakey-Milner
nbm@mithrandr.moria.org


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