Comment 4 for bug 1039398

Reviewed: https://review.openstack.org/11799
Committed: http://github.com/openstack/nova/commit/a29442d81ead759e1b33d01ef1603fa677fa86bf
Submitter: Jenkins
Branch: master

commit a29442d81ead759e1b33d01ef1603fa677fa86bf
Author: Mark McLoughlin <email address hidden>
Date: Wed Aug 22 14:56:30 2012 +0100

    Clarify nwfilter not found error message

    In bug #1039398 the user got an error message about an instance's
    nwfilter not being found, but it gave the impression that live
    migration was involved.

    The ensure_filtering_rules_for_instance() method was originally
    just used for live migration, but since:

      https://code.launchpad.net/~chemikadze/nova/driver-agnostic-restart-instances/+merge/69069

    it has also been used when re-starting the compute service when
    there are running VMs.

    Clarify the error message and the comments in the code to reflect
    this.

    Waiting up to 30 seconds before reporting an error here seems
    pretty bad. It appears this is to handle the case where the
    nwfilters get defined in a separate thread. For reference, the
    code was added by this merge:

      https://code.launchpad.net/~nttdata/nova/live-migration/+merge/44940

    For now, just add a comment explaining why we're polling for
    the existence of the nwfilter.

    Change-Id: Ieb085a6753ac72116d5f5a706fd1a908703286ad