Check for changed attribute values

Chef Infra (archive)
1

Is there anyway to check if a node attribute has changed since the last chef-client run?

My particular case is to run a rake task ONLY IF the specified git branch attribute has changed since the last chef-client run.

Thanks,
Curtis

2

On Tuesday, March 18, 2014 at 9:06 AM, Stewart, Curtis wrote:

Is there anyway to check if a node attribute has changed since the last chef-client run?

My particular case is to run a rake task ONLY IF the specified git branch attribute has changed since the last chef-client run.

Thanks,
Curtis

The old state isn’t kept around. Would it be possible to look at the state of the system to figure this out, e.g., add something like

only_if “git branch SOMETHING SOMETHING”

to your execute resource?

--
Daniel DeLeo

3

Within a chef client run? You could do something like…

last = Chef::Node.load(node.name)
if last.default[‘some-attribute’] != node.default[‘some-attribute’]
	# do something
end

This only works is you call Chef::Node.load before any recipe does a "node.save”. Substitute “override” for “default” if you’re looking at overrides.

If external to a client run and you are loading node attributes via role/cookbook/data_bag backed by git, you could use "knife node show” and compare that to what the new code would load and then execute rake.

Hope this helps.

Joe

On Mar 18, 2014, at 9:06 AM, Stewart, Curtis cstewart@momentumsi.com wrote:

Is there anyway to check if a node attribute has changed since the last chef-client run?

My particular case is to run a rake task ONLY IF the specified git branch attribute has changed since the last chef-client run.

Thanks,
Curtis

4

One way to do it would be keep some kind of changelog of the value into a file for example then ‘subscribe an action’:
file ‘/var/cache/chef/gitbranch’ do
content node[‘someattributs’]
notifies :run, 'whatever resource I want’
end

From: Joe Nuspl [mailto:nuspl@nvwls.com]
Sent: mardi 18 mars 2014 18:10
To: chef@lists.opscode.com
Subject: [chef] Re: Check for changed attribute values

Within a chef client run? You could do something like…

        last = Chef::Node.load(node.name)
        if last.default['some-attribute'] != node.default['some-attribute']
                    # do something
        end

This only works is you call Chef::Node.load before any recipe does a “node.save”. Substitute “override” for “default” if you’re looking at overrides.

If external to a client run and you are loading node attributes via role/cookbook/data_bag backed by git, you could use “knife node show” and compare that to what the new code would load and then execute rake.

Hope this helps.

        Joe

On Mar 18, 2014, at 9:06 AM, Stewart, Curtis <cstewart@momentumsi.commailto:cstewart@momentumsi.com> wrote:

Is there anyway to check if a node attribute has changed since the last chef-client run?

My particular case is to run a rake task ONLY IF the specified git branch attribute has changed since the last chef-client run.

Thanks,
Curtis

5

I really like the file idea. It allows use of notifications. We’ll try to look into that.

Thanks for the feedback!

Curtis

On Mar 19, 2014, at 9:07 AM, Jeremy Mauro <j.mauro@criteo.commailto:j.mauro@criteo.com> wrote:

One way to do it would be keep some kind of changelog of the value into a file for example then ‘subscribe an action’:
file ‘/var/cache/chef/gitbranch’ do
content node[‘someattributs’]
notifies :run, ‘whatever resource I want’
end

From: Joe Nuspl [mailto:nuspl@nvwls.com]
Sent: mardi 18 mars 2014 18:10
To: chef@lists.opscode.commailto:chef@lists.opscode.com
Subject: [chef] Re: Check for changed attribute values

Within a chef client run? You could do something like…

        last = Chef::Node.load(node.name)
        if last.default[‘some-attribute’] != node.default[‘some-attribute’]
                    # do something
        end

This only works is you call Chef::Node.load before any recipe does a "node.save”. Substitute “override” for “default” if you’re looking at overrides.

If external to a client run and you are loading node attributes via role/cookbook/data_bag backed by git, you could use "knife node show” and compare that to what the new code would load and then execute rake.

Hope this helps.

        Joe

On Mar 18, 2014, at 9:06 AM, Stewart, Curtis <cstewart@momentumsi.commailto:cstewart@momentumsi.com> wrote:

Is there anyway to check if a node attribute has changed since the last chef-client run?

My particular case is to run a rake task ONLY IF the specified git branch attribute has changed since the last chef-client run.

Thanks,
Curtis