IPA service to (re)scan SCSI devices prior to getting a list of it

[Lucas Alvares Gomes]

Reporting this bug upstream from an internal ticket [0].

Since we boot from a ramdisk the IPA service can be started prior to the SCSI devices nodes being detected in the host OS, this will make the function list_all_block_devices() from the hardware.py module to return an empty list causing the deployment to fail. The IPA service should scan the SCSI devices prior to trying to list them.

In my local tests I've tried a couple of ways to do it:

1) Sleeping 60 seconds prior to invoking list_all_block_devices()

This works but sleeping is ugly and should be avoided.

2) Modified the .service file adding a Requirement to the systemd's systemd-udev-settle.service file [1]

For some reason it didn't work, I've also tried the "Wants: " tag for the systemd unit but failed with the same error

3) invoked the "udevadm" utility prior to listing the devices, e.g:

# udevadm trigger --verbose --dry-run --type=devices --subsystem-match=scsi_disk
# udevadm settle

This works

[0] https://bugzilla.redhat.com/show_bug.cgi?id=1312187
[1] https://github.com/systemd/systemd/blob/master/units/systemd-udev-settle.service.in

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/284796
Committed: https://git.openstack.org/cgit/openstack/ironic-python-agent/commit/?id=055998c81217ededacc95f0f96a4a8bf684fbfe0
Submitter: Jenkins
Branch: master

commit 055998c81217ededacc95f0f96a4a8bf684fbfe0
Author: Lucas Alvares Gomes <email address hidden>
Date: Thu Feb 25 16:32:47 2016 +0000

    Wait for udev to settle before listing the block devices

    This patch is making the list_all_block_devices() method to wait for
    udev to settle it's event queue prior to listing the devices.

    Sometimes the ironic-python-agent service may start before all devices
    were detected and end up erroring out because it couldn't find a
    suitable disk for deployment.

    Closes-Bug: #1551300
    Change-Id: I1ae2062a711115a1ea14b79ae9ace7ddd2fff9d5

[Davanum Srinivas (DIMS) (dims-v)]

This issue was fixed in the openstack/ironic-python-agent 1.2.0 release.