nova-compute stop report state after system time changed

[John Smith]

Description
===========
On compute node,if system time changed by NTP or using cmd "date -s",change time from 14:00:00 to 12:00:00 for example,the nova-compute service will stop reporting state to controller. Then nova service-list show the nova-compute service will be down.
In fact other periodic task such as _sync_power_states, also stopped.

I think system time change should not effect nova-compute.

Steps to reproduce
==================
It is 14:00:00 now for example, change system time to 12:00:00
    $ date -s 12:00:00
then we can find there is no log in nova-compute.log for a long time.

and nova service-list show the service is down.
+--------------------------------------+------------------+------------------+----------+---------+-------+----------------------------+-----------------+-------------+
| Id | Binary | Host | Zone | Status | State | Updated_at | Disabled Reason | Forced down |
+--------------------------------------+------------------+------------------+----------+---------+-------+----------------------------+-----------------+-------------+

| 3d0ea985-bc45-4cae-b45f-876520163dfa | nova-compute | nail-5300-2 | test1 | enabled | down | 2018-01-23T09:47:48.000000 | - | False |

Expected result
===============
nova service-list show nova-compute service still up.

Actual result
=============
nova service-list show the nova-compute service is down.

Environment
===========
openstack: Pike
python: python2.7
hypervisor: libvirt + KVM

[Charlotte Han (hanrong)]

[root@nail-5300-2 oslo_service]# /usr/bin/python2 /usr/bin/nova-compute
> /usr/lib/python2.7/site-packages/eventlet/hubs/__init__.py(115)get_hub()
-> try:
(Pdb) c
> /usr/lib/python2.7/site-packages/eventlet/hubs/__init__.py(70)use_hub()
-> if mod is None:
(Pdb) w
  /usr/bin/nova-compute(6)<module>()
-> from nova.cmd.compute import main
  /usr/lib/python2.7/site-packages/nova/cmd/compute.py(28)<module>()
-> from nova.cmd import common as cmd_common
  /usr/lib/python2.7/site-packages/nova/cmd/common.py(28)<module>()
-> import nova.conf
  /usr/lib/python2.7/site-packages/nova/conf/__init__.py(27)<module>()
-> from nova.conf import cinder
  /usr/lib/python2.7/site-packages/nova/conf/cinder.py(16)<module>()
-> from keystoneauth1 import loading as ks_loading
  /usr/lib/python2.7/site-packages/keystoneauth1/loading/__init__.py(13)<module>()
-> from keystoneauth1.loading import adapter
  /usr/lib/python2.7/site-packages/keystoneauth1/loading/adapter.py(13)<module>()
-> from keystoneauth1 import adapter
  /usr/lib/python2.7/site-packages/keystoneauth1/adapter.py(18)<module>()
-> from keystoneauth1 import session
  /usr/lib/python2.7/site-packages/keystoneauth1/session.py(26)<module>()
-> import requests
  /usr/lib/python2.7/site-packages/requests/__init__.py(52)<module>()
-> from .packages.urllib3.contrib import pyopenssl
  /usr/lib/python2.7/site-packages/requests/packages/__init__.py(27)<module>()
-> from . import urllib3
  /usr/lib/python2.7/site-packages/requests/packages/urllib3/__init__.py(8)<module>()
-> from .connectionpool import (
  /usr/lib/python2.7/site-packages/requests/packages/urllib3/connectionpool.py(35)<module>()
-> from .connection import (
  /usr/lib/python2.7/site-packages/requests/packages/urllib3/connection.py(44)<module>()
-> from .util.ssl_ import (
  /usr/lib/python2.7/site-packages/requests/packages/urllib3/util/__init__.py(3)<module>()
-> from .connection import is_connection_dropped
  /usr/lib/python2.7/site-packages/requests/packages/urllib3/util/connection.py(144)<module>()
-> HAS_IPV6 = _has_ipv6('::1')
  /usr/lib/python2.7/site-packages/requests/packages/urllib3/util/connection.py(134)_has_ipv6()
-> sock = socket.socket(socket.AF_INET6)
  /usr/lib/python2.7/site-packages/eventlet/greenio/base.py(133)__init__()
-> notify_opened(fd.fileno())
  /usr/lib/python2.7/site-packages/eventlet/hubs/__init__.py(193)notify_opened()
-> hub = get_hub()
  /usr/lib/python2.7/site-packages/eventlet/hubs/__init__.py(115)get_hub()
-> try:
> /usr/lib/python2.7/site-packages/eventlet/hubs/__init__.py(70)use_hub()
-> if mod is None:
(Pdb) os.environ['EVENTLET_HUB']
*** KeyError: 'EVENTLET_HUB'
(Pdb)

os.environ['EVENTLET_HUB'] should be 'oslo_service:service_hub' when get_hub function was used for the first time.

[John Smith (wang-zengzhi)]

This issue was fixed in master, see: https://bugs.launchpad.net/nova/+bug/1510234,but not merged in PIKE.

Here I cherry pick this to PIKE:
https://review.openstack.org/#/c/537811/