Implement rfc3339 balanced formatter/parser for kube-config use

config/dateutil.py

@@ -0,0 +1,80 @@
+# Copyright 2017 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import datetime
+import math
+import re
+
+
+class TimezoneInfo(datetime.tzinfo):
+    def __init__(self, h, m):
+        self._name = "UTC"
+        if h != 0 and m != 0:
+            self._name += "%+03d:%2d" % (h, m)
+        self._delta = datetime.timedelta(hours=h, minutes=math.copysign(m, h))
+
+    def utcoffset(self, dt):
+        return self._delta
+
+    def tzname(self, dt):
+        return self._name
+
+    def dst(self, dt):
+        return datetime.timedelta(0)
+
+
+UTC = TimezoneInfo(0, 0)
+
+# ref https://www.ietf.org/rfc/rfc3339.txt
+_re_rfc3339 = re.compile(r"(\d\d\d\d)-(\d\d)-(\d\d)"        # Full time
+                         r"[ Tt]"                           # Separator
+                         r"(\d\d):(\d\d):(\d\d)([.,]\d+)?"  # partial-time
+                         r"([zZ ]|[-+]\d\d?:\d\d)?",        # time-offset
+                         re.VERBOSE + re.IGNORECASE)
+_re_timezone = re.compile(r"([-+])(\d\d?):?(\d\d)?")
+
+
+def parse_rfc3339(s):
+    if type(s) == datetime.datetime:
+        # no need to parse it, just make sure it has a timezone.
+        if not s.tzinfo:
+            return s.replace(tzinfo=UTC)
+        return s
+    groups = _re_rfc3339.search(s).groups()
+    dt = [0] * 7
+    for x in range(6):
+        dt[x] = int(groups[x])
+    if groups[6] is not None:
+        dt[6] = int(groups[6])
+    tz = UTC
+    if groups[7] is not None and groups[7] != 'Z' and groups[7] != 'z':
+        tz_groups = _re_timezone.search(groups[7]).groups()
+        hour = int(tz_groups[1])
+        minute = 0
+        if tz_groups[0] == "-":
+            hour *= -1
+        if tz_groups[2]:
+            minute = int(tz_groups[2])
+        tz = TimezoneInfo(hour, minute)
+    return datetime.datetime(
+        year=dt[0], month=dt[1], day=dt[2],
+        hour=dt[3], minute=dt[4], second=dt[5],
+        microsecond=dt[6], tzinfo=tz)
+
+
+def format_rfc3339(date_time):
+    if date_time.tzinfo is None:
+        date_time = date_time.replace(tzinfo=UTC)
+    date_time = date_time.astimezone(UTC)
+    return date_time.strftime('%Y-%m-%dT%H:%M:%SZ')

config/kube_config.py

@@ -17,19 +17,17 @@
 import datetime
 import os
 import tempfile
-import time
 
 import google.auth
 import google.auth.transport.requests
 import urllib3
 import yaml
 
 from kubernetes.client import ApiClient, ConfigurationObject, configuration
-
+from .dateutil import parse_rfc3339, format_rfc3339, UTC
 from .config_exception import ConfigException
-from .rfc3339 import tf_from_timestamp, timestamp_from_tf
 
-EXPIRY_SKEW_PREVENTION_DELAY_S = 600
+EXPIRY_SKEW_PREVENTION_DELAY = datetime.timedelta(minutes=5)
 KUBE_CONFIG_DEFAULT_LOCATION = os.environ.get('KUBECONFIG', '~/.kube/config')
 _temp_files = {}
 
@@ -60,14 +58,8 @@ def _create_temp_file_with_content(content):
 
 
 def _is_expired(expiry):
-    tf = tf_from_timestamp(expiry)
-    n = time.time()
-    return tf + EXPIRY_SKEW_PREVENTION_DELAY_S <= n
-
-
-def _datetime_to_rfc3339(dt):
-    tf = (dt - datetime.datetime.utcfromtimestamp(0)).total_seconds()
-    return timestamp_from_tf(tf, time_offset="Z")
+    return ((parse_rfc3339(expiry) + EXPIRY_SKEW_PREVENTION_DELAY) <=
+            datetime.datetime.utcnow().replace(tzinfo=UTC))
 
 
 class FileOrData(object):
@@ -211,7 +203,7 @@ def _refresh_gcp_token(self):
         provider = self._user['auth-provider']['config']
         credentials = self._get_google_credentials()
         provider.value['access-token'] = credentials.token
-        provider.value['expiry'] = _datetime_to_rfc3339(credentials.expiry)
+        provider.value['expiry'] = format_rfc3339(credentials.expiry)
         if self._config_persister:
             self._config_persister(self._config.value)
 
@@ -353,8 +345,8 @@ def load_kube_config(config_file=None, context=None,
         from config file will be used.
     :param client_configuration: The kubernetes.client.ConfigurationObject to
         set configs to.
-    :param persist_config: If True and config changed (e.g. GCP token refresh)
-        the provided config file will be updated.
+    :param persist_config: IF True, config file will be updated when changed
+        (e.g GCP token refresh).
     """
 
     if config_file is None: