Support non-UTC timestamps in changes-since filter

Fixes nova aspect of lp 837464

Prevously only Zulu time was supported in the changes-since filter,
i.e. timestamps formatted as %Y-%m-%dT%H:%M:%SZ

We now support arbitrary timezones, with the offset from UTC expressed
via the ISO 8601 ±hh:mm notation.

Microsecond accurracy is also optionally supported in timestamps.

Notes:

- nova.utils.parse_isotime(), isotime() & normalized_time() are
  prime candidates for promotion to openstack-common, as these
  methods were duplicated from my corresponding glance patch:

    https://review.openstack.org/#change,4198

- this patch introduces a new dependency on python-iso8601, which
  has already been packaged for Fedora, EPEL and Ubuntu/Debian.

Change-Id: I89b45f4f3d910606c578d927420f78cea94f4e3b

1 files changed, 19 insertions, 4 deletions

diff --git a/nova/utils.py b/nova/utils.py
index 96f0a57f0..85f39dbe0 100644
--- a/nova/utils.py
+++ b/nova/utils.py
@@ -44,6 +44,7 @@ from eventlet import event
 from eventlet import greenthread
 from eventlet import semaphore
 from eventlet.green import subprocess
+import iso8601
 import netaddr
 
 from nova import exception
@@ -53,7 +54,7 @@ from nova.openstack.common import cfg
 
 
 LOG = logging.getLogger(__name__)
-ISO_TIME_FORMAT = "%Y-%m-%dT%H:%M:%SZ"
+ISO_TIME_FORMAT = "%Y-%m-%dT%H:%M:%S"
 PERFECT_TIME_FORMAT = "%Y-%m-%dT%H:%M:%S.%f"
 FLAGS = flags.FLAGS
 
@@ -534,13 +535,27 @@ def parse_strtime(timestr, fmt=PERFECT_TIME_FORMAT):
 
 
 def isotime(at=None):
-    """Returns iso formatted utcnow."""
-    return strtime(at, ISO_TIME_FORMAT)
+    """Stringify time in ISO 8601 format"""
+    if not at:
+        at = datetime.datetime.utcnow()
+    str = at.strftime(ISO_TIME_FORMAT)
+    tz = at.tzinfo.tzname(None) if at.tzinfo else 'UTC'
+    str += ('Z' if tz == 'UTC' else tz)
+    return str
 
 
 def parse_isotime(timestr):
     """Turn an iso formatted time back into a datetime."""
-    return parse_strtime(timestr, ISO_TIME_FORMAT)
+    try:
+        return iso8601.parse_date(timestr)
+    except (iso8601.ParseError, TypeError) as e:
+        raise ValueError(e.message)
+
+
+def normalize_time(timestamp):
+    """Normalize time in arbitrary timezone to UTC"""
+    offset = timestamp.utcoffset()
+    return timestamp.replace(tzinfo=None) - offset if offset else timestamp
 
 
 def parse_mailmap(mailmap='.mailmap'):