nova docker driver cannot find cgroup in /proc/mounts on RHEL

[Boden R]

I'm using the nova docker driver on RHEL 3.10.11-1.el6.x86_64 (rebuilt kernel). Based on the format of /proc/mounts on RHEL, the cgroup devices path cannot be found.

On my box the line in /proc/mounts for cgroups looks like this:

none /sys/fs/cgroup cgroup rw,relatime,perf_event,blkio,net_cls,freezer,devices,memory,cpuacct,cpu,cpuset,clone_children 0 0

In the docker driver the method which searches /proc/mounts for the cgroup path looks like this:

    def _find_cgroup_devices_path(self):
        for ln in open('/proc/mounts'):
            if ln.startswith('cgroup ') and 'devices' in ln:
                return ln.split(' ')[1]

Therefore the method cannot find my cgroup path. I hacked around this with a 1 LOC change to the _find_cgroup_devices_path method which looks for 'cgroup' as the 3rd item in the line split:

if ln.split(' ')[2] == 'cgroup' and 'devices' in ln:

The update method in its entirety looks like:

169 def _find_cgroup_devices_path(self):
170 for ln in open('/proc/mounts'):
171 if ln.split(' ')[2] == 'cgroup' and 'devices' in ln:
172 return ln.split(' ')[1]

Based on the format in /proc/mounts on my ubuntu box, this change *should* work on ubuntu as well as rhel.

I did read that docker is only supported with devstack + unbuntu, so I realize this defect may get deferred or even closed. However I wanted to surface it as I believe future efforts of openstack + docker will need to consider non-ubuntu + devstack envs.

[Nicolas Fillot (nicolas.fillot)]

I confirm this bug, this also affects Debian (Jessie)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/62182

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/62182
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=21045a58497818f76f880fe74b3eb5ab09088cf3
Submitter: Jenkins
Branch: master

commit 21045a58497818f76f880fe74b3eb5ab09088cf3
Author: Daniel Kuffner <email address hidden>
Date: Sat Dec 14 18:31:26 2013 +0100

    nova docker driver cannot find cgroup in /proc/mounts on RHEL

    In order to support the docker hypervisor on rhel/centos or fedora
    we had to adapt the function which resolves the cgroup path.

    Change-Id: Ie24028f822d91d65d4f90a7941e7b11874a3b425
    Closes-Bug: #1243101