Comment 9 for bug 1510234

Reviewed: https://review.openstack.org/434327
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=a7505ee648b22f5827117bcc1192b5654c29cf9c
Submitter: Jenkins
Branch: master

commit a7505ee648b22f5827117bcc1192b5654c29cf9c
Author: Roman Podoliaka <email address hidden>
Date: Wed Feb 15 16:47:42 2017 +0200

    Make eventlet hub use a monotonic clock

    If system time is adjusted first forward and then backward while a
    nova service is running (e.g. nova-compute), then there is a high
    probability, that periodic tasks will stop for the duration of time
    the system clock was adjusted backward.

    This was supposed to be fixed by the following patch to oslo.service
    https://review.openstack.org/#/c/286838/ , but the order of imports
    in unit tests and production code is different, so nova services
    end up starting with the default eventlet hub, that does not use a
    monotonic clock and, thus, is affected by changes of system time.

    Testing this is problematic, as it's a subject of imports order and
    is not reproduced in functional or unit tests (oslo_service is always
    imported earlier than eventlet hub is initialized, so it just does
    "the right thing"). The alternative is to make an assertion when
    services start.

    Closes-Bug: #1510234

    Change-Id: I110cf31ad2a0c74a0cf30ec08bd94d3a56727b39