crowbar/barclamp-swift — pull request #80 by VictorLowther (2013-06-06 16:46:15+00:00)
Title: Rework how we allocate disks to barclamps. Will close DE1120 and DE1162. [3/8]

For many releases, Crowbar has built node\[:crowbar\]\[:disks\] at node
discovery time, and the Chef cookbooks have used what is in that array
to determine what drives they can use. This scheme has a few
shortcomings:

1. The code always assumed that /dev/sda was going to be the boot
device.
2. The list was built at discovery time, and so it was blind to any
changes in the disk topology that would happen when the raid
barclamp did its thing
3. The only choices for a disk role were OS and Storage, leading to
all sorts of fun when multiple roles wanted to grab a physical
disk or twenty to get all Big Data.

To fix the above shortcomings, I have replaced node[:crowbar][:disks]
with a set of methods on the
BarclampInventory::Barclamp::Inventory::Disk class (and its objects)
that let you:

1. Get a list of all unclaimed fixed nonremovable disks on a node.
2. Get a list of all disks that have been claimed by a barclamp on a
node.
3. Claim a disk for a barclamp.
4. Release a claim for a disk.

To make sure that the claims for a disk stay relatively sane, there
are some restrictions on when you can claim a disk:

1. You cannot claim a disk before the RAID barclamp has finished
making any changes it is going to make to a system.
2. You can only make and release claims to a disk on the node that
has the disk. In practice, this means that the only place you can
claim a disk is in a recipe running on the node that has the disks
to be claimed or released.

How it is implemented:

All claims to a disk are tracked on
node\[:crowbar\_wall\]\[:claimed\_disks\]\[disk.unique\_name\]
disk.unique_name is a method that looks up as unique a name as
possible for the disk, making the claim and release machinery as
insensitive to the vagaries of device naming as you can reasonably get
on a modern Linux system.

Related changes made in this patch series:

* Killed off the UI code in the Cinder barclamp that attempted to let you assign specific
disks to a role. Since we were using raw device names that were
prone to change over the node discovery process, and that we do
not know what the boot device will be until after the node is
allocated and we set up RAID (if applicable) on the system, the
device names that the UI was presenting would only be accurate
after the node was up and transitioned into a ready state. The UI
now only allows the local (which maps to a loopback-mounted Large
File that has been turned into a PV for Cinder's VG), first (which
picks the first unclaimed raw device), and all (which grabs all
unclaimed raw devices).
* Killed nova-volume entirely. It would have required the same
changes that Cinder required.

chef/data_bags/crowbar/bc-template-swift.json | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

Crowbar-Pull-ID: b33d4f791a3432f0d3d2d4ea58a1c80f9ce6c95e

Crowbar-Release: pebbles