On 16/05/12 13:07, Mister IT Guru wrote:
Good Afternoon Puppet List,
I'm investigating the possibility of using puppet to take over an already
existing cluster of servers. Ordinarily this doesn't sound like anything out
the ordinary, but I've had my hands tied by the cluster owner saying he doesn't
want anything to break/fail while I'm wrestling the cluster to be under my
control.
Ordinarily, I'd say lets upgrade your working practices while we're at it, and properly
manage your whole workflow, manage access and manage who can make changes. Lets start by
rebuilding your boxes to specification, and migrating your existing data over. Sounds
great, "Client says no" huh? - Now I need to rethink my strategy.
I was planning on using my current manifests, but I think I'll end up over
writing some config file that had a critical setting in it, or change a
password somewhere. Usually, I'm not too worried about that, but it did occur
to me that I don't have any real sanity checks in my modules.
• Are there any recommended ways of using puppet to take over a
production environment?
I've done this a lot. Unfortunately the only way you'll be absolutely
sure that Puppet isn't breaking something is to look at the log/report
of each host. You can do breadth first: get Puppet everywhere just
managing itself, then slowly add managed resources to Puppet. Or you can
do depth first: get Puppet managing everything on one machine, prove to
your cluster manager that this one machine still works, then teach other
people how to convert a cluster node to Puppet and check the logs (might
be faster in your case).
• How can I ensure that when I'm spreading my manifests across the
globe, I mean cluster, that any changes can be reverted?
Not easily... Puppet has no inbuilt 'revert' functionality and how do
you know what state everything is in to start with? You could use Ralsh
to query the state of all the resources you want to manage before you
apply any changes. The log of a run will show a resource's previous
state and the state Puppet changed it to as well. Also be aware that the
log is dependent on how the provider reports what it's done. Most of the
native Puppet resource types are ok (Service changed 'stopped' to
'running') but other native types (I can't think of any off hand) could
simply say "Changed 'absent' to 'present'" and that could be a bit
ambiguous depending on the provider's definition of "absent".
• I understand that every file puppet changes, gets backed up?
Where? (embarrassed he doesn't know!)
Look at the filebucket feature, generally stored on the Puppet Master in
/var/lib/puppet/bucket:
http://docs.puppetlabs.com/references/2.7.0/type.html#filebucket
• Finally, can I force puppet to replace changed files, or is this a
manual process?
I'm not sure what you mean by changed files. If you have Puppet manage a
file's contents with the File type, it will continually put in that file
what it thinks should be in there. Other providers can make inline edits
of files, like Augeas or PuppetLab's Parsedfile.
Thanks,
-- Mister Guru
--
Luke Bigum
Information Systems
Ph: +44 (0) 20 3192 2520
[email protected] | http://www.lmax.com
LMAX, Yellow Building, 1A Nicholas Road, London W11 4AN
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