Sometimes cronjobs fail to run successfully because a required server (like a database or ftp server) is temporarily unavailable due to power failures, hardware failures, software failures, network outages, choice of operating system, pilot error, and the like.
Typically, this results in someone being forced to examine crontabs and error reports, determine which cronjobs really need to be run, and then run them manually. This happened to me twice in one week. I didn't want it to happen again. Cronjobs are meant to be automated and I want them to stay that way.
This is the rationale for noexcuses. It keeps track of cronjobs
that have failed and keeps running them until they succeed. All you have to
do is look at your crontabs, identify the
cronjobs-that-must-succeed-no-matter-what and insert
before the command.
Then, when cron runs noexcuses, noexcuses will
run the given cronjob. If the cronjob fails, noexcuses becomes a
daemon that will retry the cronjob regularly until it succeeds. Even if the
cron host is rebooted before the cronjob succeeds, noexcuses lets
you restart all of the outstanding cronjobs. If you can't wait for the cron
host to reboot, its outstanding cronjobs can be relocated to another cron
host and be forgotten on the original host when it finally reboots. Also, if
the cron host is down for a while, noexcuses can tell you which
cronjobs missed out on running while it was down and run them. The optional
/etc/init.d/noexcuses can make this happen
automatically at boot time.
In other words, noexcuses is a free, lightweight, fine-grained, unobtrusive, high-availability tool for cronjobs. Or rather, it's a high-recoverability tool for cronjobs which can either be incorporated into a highly available system or used in the absence of one.
noexcuses is freely available under the GNU General Public License, either version 2 of the License, or (at your option) any later version.
For more information read the manual entry in the Documentation section.
noexcuses is written in Perl and should run on any UNIX-like system where cron runs. There are no dependencies on any non-standard Perl modules.
There is a manual entry:
||-||the noexcuses(1) manpage|