Improve the liveness checking for services

With this modification both nova-manage and scheduler use the flag
service_down_time and check positive and negative values in a
correct way.
Fixes bug: 867674.

Change-Id: I15c48d80cafa2089cd228c09c61b0a1e513730e8

2 files changed, 11 insertions, 4 deletions

diff --git a/nova/scheduler/driver.py b/nova/scheduler/driver.py
index 7bf26cfdf..577503cd8 100644
--- a/nova/scheduler/driver.py
+++ b/nova/scheduler/driver.py
@@ -21,8 +21,6 @@
 Scheduler base class that all Schedulers should inherit from
 """
 
-import datetime
-
 from nova import db
 from nova import exception
 from nova import flags
@@ -143,8 +141,8 @@ class Scheduler(object):
         """Check whether a service is up based on last heartbeat."""
         last_heartbeat = service['updated_at'] or service['created_at']
         # Timestamps in DB are UTC.
-        elapsed = utils.utcnow() - last_heartbeat
-        return elapsed < datetime.timedelta(seconds=FLAGS.service_down_time)
+        elapsed = utils.total_seconds(utils.utcnow() - last_heartbeat)
+        return abs(elapsed) <= FLAGS.service_down_time
 
     def hosts_up(self, context, topic):
         """Return the list of hosts that have a running service for topic."""
diff --git a/nova/utils.py b/nova/utils.py
index 7d34a87d8..ad585ba1c 100644
--- a/nova/utils.py
+++ b/nova/utils.py
@@ -1009,3 +1009,12 @@ def make_dev_path(dev, partition=None, base='/dev'):
     if partition:
         path += str(partition)
     return path
+
+
+def total_seconds(td):
+    """Local total_seconds implementation for compatibility with python 2.6"""
+    if hasattr(td, 'total_seconds'):
+        return td.total_seconds()
+    else:
+        return ((td.days * 86400 + td.seconds) * 10 ** 6 +
+                td.microseconds) / 10.0 ** 6