Re: cfengine cronjob on pool of servers

[Brendan Strejcek]

Christopher Browne wrote:

> We need to schedule a script to run on ONLY ONE of the N hosts. The
> catch is that any host could be down at any moment in the future, so
> schedulling cronjob on one of the hosts is not a reliable option. Also
> the job cannot be run more that once (ie cannot be run from multiple
> hosts).

David Masterson wrote:

> Simplisticly, that could probably be done by creating (lock) files.
> The cfengine host that creates the file first wins. Of course, this
> assumes an NFS setup

You could also use a database or a CGI application. There is no reason
to depend on NFS to keep state. This is not an easy problem though. For
example, what if the host providing the locking mechanism (NFS server,
database server, whatever) is down? The more important the service, the
more redundancy you need, and that costs, particularly when you are
talking about read-write data (such as locking).

Best,
Brendan

--
Senior System Administrator
The University of Chicago
Department of Computer Science

http://www.cs.uchicago.edu/people/brendan
http://praksys.blogspot.com/