Handle empty dnsmasq pidfile properly

[Stanislaw Pitucha]

In some extreme conditions dnsmasq's pidfile can be empty, resulting in an exception when trying to convert the contents into integer. Dnsmasq doesn't try to do an atomic creation+write, so for example XFS has a chance of leaving the file empty after a complete system crash.

[Stanislaw Pitucha (stanislaw-pitucha)]

Patch submitted https://review.openstack.org/#change,788

[Openstack Gerrit (openstack-gerrit)]

Reviewed: https://review.openstack.org/788
Committed: http://github.com/openstack/nova/commit/a25f106c2f824d7d03bf1161da72f66fe4be5a9c
Submitter: Jenkins
Branch: master

 status fixcommitted
 done

commit a25f106c2f824d7d03bf1161da72f66fe4be5a9c
Author: Yun Shen <email address hidden>
Date: Thu Sep 29 12:09:37 2011 +0100

    Handle pidfile exception for dnsmasq

    Capture the exception in dnsmasq_pid_for method. If the pidfile cannot be read
    for some reason, it should be treated as if it does not exist. This prevents
    issues where the filesystem write delay leaves the file created but empty.
    Fixes bug 865399.

    Change-Id: I3b0f1211762696f925ae32d785ffa6a35c5e1d6b

[Openstack Gerrit (openstack-gerrit)]

Reviewed: https://review.openstack.org/1082
Committed: http://github.com/openstack/nova/commit/ad4eef0a0b296652f8ce08d86a10dea8a40b005b
Submitter: Jenkins
Branch: stable/diablo

 status fixcommitted
 done

commit ad4eef0a0b296652f8ce08d86a10dea8a40b005b
Author: Yun Shen <email address hidden>
Date: Thu Sep 29 12:09:37 2011 +0100

    Handle pidfile exception for dnsmasq

    Capture the exception in dnsmasq_pid_for method. If the pidfile cannot be read
    for some reason, it should be treated as if it does not exist. This prevents
    issues where the filesystem write delay leaves the file created but empty.
    Fixes bug 865399.

    (cherry picked from commit a25f106c2f824d7d03bf1161da72f66fe4be5a9c)

    Change-Id: Ifd79c7143060702bfe359f0e0a35867c685e27df

[Martin Pitt (pitti)]

Hello Stanislaw, or anyone else affected,

Accepted nova into oneiric-proposed, the package will build now and be available in a few hours. Please test and give feedback here. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you in advance!

[Adam Gandelman (gandelman-a)]

Verified the package nova-network 2011.3+git20111117-0ubuntu1 in oneiric-proposed resolves this issue without regression.

As a test case, I've run one instance, killed the dnsmasq process that nova-network creates, create an empty pid file in place of the original dnsmasq pid file, and run another instance on the same host. The dnsmasq process and successfully restarted without exceptions. Log available: http://paste.ubuntu.com/775578/

The same test case prior to this fix results in the following traceback in nova-network.log - http://paste.ubuntu.com/775581/