use of threading in libvirt driver causes deadlock when connecting to libvirtd

[Michael Kerrin]

the libvirt driver was running into this issue https://bitbucket.org/eventlet/eventlet/issue/137/use-of-threading-locks-causes-deadlock when trying to connect to the libvirtd daemon.

the driver has logging messages during the _connect method which was called within a native thread. The logging code takes out a eventlet lock and mixing OS native threads and eventlet locks causes deadlocks due to the above eventlet bug. The resulting deadlock was enough to hang the nova-compute process.

[Matt Riedemann (mriedem)]

Patch: https://review.openstack.org/#/c/57000/

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/57000
Committed: http://github.com/openstack/nova/commit/e4b0d8e9446ad3ad3a514b9cf65722f6ed95888d
Submitter: Jenkins
Branch: master

commit e4b0d8e9446ad3ad3a514b9cf65722f6ed95888d
Author: Michael Kerrin <email address hidden>
Date: Mon Nov 18 17:25:50 2013 +0000

    Use of logging in native thread causes deadlock connecting to libvirtd

    When connecting to libvirtd daemon we were calling the _connect
    method in a native thread. The use of logging in this method hit this
    bug in eventlet https://bitbucket.org/eventlet/eventlet/issue/137/
    causing nova-compute to hang.

    Closes-Bug: #1252409

    Change-Id: I0d22c3ed1b3288aeb1afae130f11a4f38dc6440a

[Matt Riedemann (mriedem)]

I'm looking to backport this to stable/havana but it requires (in order):

https://review.openstack.org/#/c/55866/
https://review.openstack.org/#/c/54595/

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/havana
Review: https://review.openstack.org/112421

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/112421
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=48d19691e21ddf7f52d8f80c67353e6a3e54552e
Submitter: Jenkins
Branch: stable/havana

commit 48d19691e21ddf7f52d8f80c67353e6a3e54552e
Author: Michael Kerrin <email address hidden>
Date: Mon Nov 18 17:25:50 2013 +0000

    Use of logging in native thread causes deadlock connecting to libvirtd

    When connecting to libvirtd daemon we were calling the _connect
    method in a native thread. The use of logging in this method hit this
    bug in eventlet https://bitbucket.org/eventlet/eventlet/issue/137/
    causing nova-compute to hang.

    Closes-Bug: #1252409

    Conflicts:
            nova/virt/libvirt/driver.py

    NOTE(mriedem): The conflict is due to set_host_enabled
    being used in the original change in Icehouse and the
    option rename for libvirt_nonblocking.

    Change-Id: I0d22c3ed1b3288aeb1afae130f11a4f38dc6440a
    (cherry picked from commit e4b0d8e9446ad3ad3a514b9cf65722f6ed95888d)