RE: Re: Using time stamps in a template?

Chef Infra (archive)
1

Interesting thought. Basically, you are suggesting that the template generate an intermediate file, and then in a separate step, I'd use something like sed or awk to insert the actual time stamp.

Thank you! I knew somebody had a solution for my problem!

Kevin Keane

The NetTech

http://www.4nettech.com

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-----Original message-----
From: Noah Kantrowitz noah@coderanger.net
Sent: Monday 25th May 2015 12:20
To: chef@lists.opscode.com
Subject: [chef] Re: Using time stamps in a template?

You would have to implement the idempotence check yourself separate from the file contents. You could do something like make a template with the serial always set to 0, and use a notification that when that template changes trigger a ruby_block to bump the serial number on disk and write out the real template.

--Noah

On May 25, 2015, at 8:26 AM, Kevin Keane Subscription subscription@kkeane.com wrote:

I am looking for a way to put a time stamp into a template, without causing the file to be regenerated on each chef run. I want the time stamp to be updated only if something else has changed in the template, as well.

The use case is for generating a DNS zone file and updating the serial number only when there was a change.

Is there a common solution for this problem in Chef?

Kevin Keane

The NetTech

760-721-8339

http://www.4nettech.com

Our values: Privacy, Liberty, Justice

See https://www.4nettech.com/corp/the-nettech-values.html

2

No, I would have two template resources, one acting as an idempotence check for the sans-serial data and the other is the full content with serial. A better approach is to try to keep the serial in its own file and use an include. A rough example of the first (not actually going to test this):

template '/etc/bind/myzone.partial' do
source 'whatever.erb'
variables serial: 0
notifies :run, 'ruby_block[dns trick]', :immediately
end

ruby_block 'dns trick' do
block do
path = '/etc/bind/myzone.serial'
IO.write(path, IO.read(path).to_i + 1)
end
end

template '/etc/bind/myzone' do
source 'whatever.erb'
variables lazy { {serial: IO.read('/etc/bind/myzone.serial') } }
end

This shows two templates, when the serial=0 one updates it bumps the serial file, which the second will use to generate the real zone config. The second approach might be possible with $INCLUDE in BIND but I'm not familiar enough with its usage to show an example.

--Noah

On May 25, 2015, at 4:10 PM, Kevin Keane Subscription subscription@kkeane.com wrote:

Interesting thought. Basically, you are suggesting that the template generate an intermediate file, and then in a separate step, I'd use something like sed or awk to insert the actual time stamp.

Thank you! I knew somebody had a solution for my problem!

Kevin Keane

The NetTech

http://www.4nettech.com

Our values: Privacy, Liberty, Justice

See https://www.4nettech.com/corp/the-nettech-values.html

-----Original message-----
From: Noah Kantrowitz noah@coderanger.net
Sent: Monday 25th May 2015 12:20
To: chef@lists.opscode.com
Subject: [chef] Re: Using time stamps in a template?

You would have to implement the idempotence check yourself separate from the file contents. You could do something like make a template with the serial always set to 0, and use a notification that when that template changes trigger a ruby_block to bump the serial number on disk and write out the real template.

--Noah

On May 25, 2015, at 8:26 AM, Kevin Keane Subscription subscription@kkeane.com wrote:

I am looking for a way to put a time stamp into a template, without causing the file to be regenerated on each chef run. I want the time stamp to be updated only if something else has changed in the template, as well.

The use case is for generating a DNS zone file and updating the serial number only when there was a change.

Is there a common solution for this problem in Chef?

Kevin Keane

The NetTech

760-721-8339

http://www.4nettech.com

Our values: Privacy, Liberty, Justice

See https://www.4nettech.com/corp/the-nettech-values.html