Thank you for nice abstraction for the image dir resource.
I wasn't able to coin it myself. Chef is too new for me. I had to keep a
lot in my head at time.
My minimal goal is to express all in chef somehow.
Chef state based model has one big plus such recipes enforce a developer to
do very adoptable
scrips. And the faw of this approach makes code bloat.
Look at my final solution based on standard resources. It's a real crap.
disk = vm_cfg.disk.folder + '/' + vm_cfg.disk.name
execute "cp #{ vm_cfg.disk.template } #{ disk }" do
not_if "[ -f #{ disk } ]"
end
execute "virsh shutdown #{ name }" do
only_if "virsh domstate #{ name } | grep -c running"
end
ruby_block "resize disk" do
block do
resize_raw_image(disk, vm_cfg.disk.size_mb)
end
not_if { File.size(disk) == vm_cfg.disk.size_mb * 1024 * 1024 }
end
execute "check loop is free" do
command "losetup -d /dev/loop0"
only_if "losetup -a | grep /dev/loop0"
end
execute "bind image with device" do
command "losetup /dev/loop0 #{ disk }"
not_if "losetup /dev/loop0 | grep #{disk}"
end
execute "clear kernel cache" do
command "partprobe /dev/loop0"
end
directory "/tmp/mount-vm-image"
if previous fail
execute "umount image" do
command "umount /dev/loop0p1"
only_if "df | grep /tmp/mount-vm-image"
end
execute "mount image" do
command "mount -t ext4 /dev/loop0p1 /tmp/mount-vm-image"
end
template "/tmp/mount-vm-image/etc/hostname" do
source "hostname.erb"
variables ({ :hostname => vm_fqdn(node.net, name) })
end
execute "unmount image" do
command "umount /dev/loop0p1"
end
directory "/tmp/mount-vm-image" do
action :delete
end
execute " free loop" do
command "losetup -d /dev/loop0"
end
On Mon, Nov 25, 2013 at 8:57 PM, Daniel DeLeo dan@kallistec.com wrote:
On Monday, November 25, 2013 at 8:47 AM, Sean OMeara wrote:
Hi Daneel.
It's possible that Chef (or any other CM tool) may not be the best choice
in tooling to do this.
That being said, it totally is possible.
You'll want to create a custom resource type for this, (use the LWRP DSL),
and implement the transactional logic in the provider. Always keep in mind
that Chef is about ensuring state. "Test for state, take action to repair*
IF NEEDED*"
The state you wish to ensure is "A directory exists inside an unmounted
image".
To pull this off, you'll need to mount the image, check for the directory,
repair if needed, then clean up after yourself.
You'll need to do this on every Chef run.
Stating the problem like that, I'd personally choose focus on artifact
generation using classic procedural scripting out of band of Chef.
If you do choose to implement this with a Chef provider, you'd want to
start by thinking about the interface when using the custom resource.
Something like this:
somerecipe.rb
image_directory "example image" do
path '/srv/images/blackbox.img'
directory '/var/log/twiddlybits'
action :create
end
If you want to use the LWRP DSL, the above example will need to be in
cookbook named "image",
If you'd rather use the full blown class interface (a so called HWRP), you
can ship it in a cookbook with any name.
Either way, you'll want to implement the transactional logic in the
provider, and you'll probably want to use mixlib::shellout to handle stdout.
Don't forget to call new_resource.updated_by_last_action(true) if you have
to make the directory.
Good luck!
-s
This is all good advice. If it’s not possible for you to do in a
reasonable amount of time, you should look at using not_if or only_if
guards on your execute resources so that they’ll always do the right thing
instead of chaining notifies together.
On Mon, Nov 25, 2013 at 8:03 AM, Daneel Yaitskov <rtfm.rtfm.rtfm@gmail.com
wrote:
All,
I faced with complex relation between resources.
Let's look at this:
remote_file copies a disk image
execute losetup binds the image with a device
execute mount attaches the device to the filesystem
directory creates folder on the mounted image.
This recipe is not reliable because of an exception in a middle of the
recipe
requires manual intervention to reset environment.
I.e. I should unmount the device because the first resource would write to
mounted .
I could wrap all these resources inside of one ruby_block and use a lot
nested begin/ensure
but then I lose any profit of the chef.
I want to preserve linear structure of the recipe and set rollback
callbacks on successfully executed resources.
Is there any standard way?
--
Daneel S. Yaitskov
--
Daniel DeLeo
--
Daneel S. Yaitskov