use email.utils to parse date and time

biothings/hub/dataload/dumper.py

@@ -1,5 +1,6 @@
 import asyncio
 import cgi
+import email.utils
 import inspect
 import os
 import pprint
@@ -772,34 +773,15 @@ def remote_is_better(self, remotefile, localfile):
             return True
         # In accordance with RFC 7231
         # The reason we are not using strptime is that it's locale sensitive
-        # and changing locale and then changing it bace is not thread safe.
-        # Although at the moment we are using Tornado which uses coroutines,
-        # we still have threads (for reasons) and down the line we may move
-        # to a different framework. The Dumper should be agnostic of what
-        # it is running on. Hence parsing the dates manually
-        last_modified_str = res.headers[self.LAST_MODIFIED]
-        http_date_regex = re.compile(
-            r'(?:Mon|Tue|Wed|Thu|Fri|Sat|Sun), '
-            r'(?P<day>\d{2}) '
-            r'(?P<month>Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec) '
-            r'(?P<year>\d{4}) '
-            r'(?P<hour>\d{2}):(?P<minute>\d{2}):(?P<second>\d{2}) '
-            r'GMT'
-        )
-        match = http_date_regex.match(last_modified_str)
-        if not match:
-            self.logger.warning("Last-Modified is in an obsolete format")
-            return True
-        month_map = {'Jan': 1, 'Feb': 2, 'Mar':3, 'Apr': 4, 'May': 5, 'Jun':6,
-                     'Jul': 7, 'Aug': 8, 'Sep': 9, 'Oct': 10, 'Nov': 11, 'Dec': 12}
-        dt_kwargs = {'tzinfo': timezone.utc}
-        for k in ('year', 'day', 'hour', 'minute', 'second'):
-            dt_kwargs[k] = int(match.group(k))
-        dt_kwargs['month'] = month_map[match.group('month')]
-        # RFC 7231 defines leap seconds
-        if dt_kwargs['second'] == 60:
-            dt_kwargs['second'] = 59
-        dt = datetime(**dt_kwargs)
+        # and changing locale and then changing it back is not thread safe.
+        dt_tuple = email.utils.parsedate(res.headers[self.LAST_MODIFIED])
+        # this utility function supports more malformed data so using this one
+        if dt_tuple[5] == 60:
+            _ = list(dt_tuple)
+            _[5] = 59
+            dt_tuple = tuple(_)
+        # deal with potential leap second as defined in the RFC, good enough solution
+        dt = datetime(*dt_tuple[:6], tzinfo=timezone.utc)  # HTTP-date is always in UTC
         remote_lastmodified = dt.timestamp()
         try:
             res = os.stat(localfile)