Use If-Modified-Since HTTP-header and avoid downloading a remote index if the local copy is recent enough.

2 files changed, 62 insertions, 7 deletions

diff --git a/pym/portage/dbapi/bintree.py b/pym/portage/dbapi/bintree.py
index 9527b0766..16ae8eccf 100644
--- a/pym/portage/dbapi/bintree.py
+++ b/pym/portage/dbapi/bintree.py
@@ -54,6 +54,11 @@ if sys.hexversion >= 0x3000000:
 else:
 	_unicode = unicode
 
+class UseCachedCopyOfRemoteIndex(Exception):
+	# If the local copy is recent enough
+	# then fetching the remote index can be skipped.
+	pass
+
 class bindbapi(fakedbapi):
 	_known_keys = frozenset(list(fakedbapi._known_keys) + \
 		["CHOST", "repository", "USE"])
@@ -852,6 +857,7 @@ class binarytree(object):
 				if e.errno != errno.ENOENT:
 					raise
 			local_timestamp = pkgindex.header.get("TIMESTAMP", None)
+			remote_timestamp = None
 			rmt_idx = self._new_pkgindex()
 			proc = None
 			tmp_filename = None
@@ -861,8 +867,13 @@ class binarytree(object):
 				# slash, so join manually...
 				url = base_url.rstrip("/") + "/Packages"
 				try:
-					f = _urlopen(url)
-				except IOError:
+					f = _urlopen(url, if_modified_since=local_timestamp)
+					if hasattr(f, 'headers') and f.headers.get('timestamp', ''):
+						remote_timestamp = f.headers.get('timestamp')
+				except IOError as err:
+					if hasattr(err, 'code') and err.code == 304: # not modified (since local_timestamp)
+						raise UseCachedCopyOfRemoteIndex()
+
 					path = parsed_url.path.rstrip("/") + "/Packages"
 
 					if parsed_url.scheme == 'sftp':
@@ -903,7 +914,8 @@ class binarytree(object):
 					_encodings['repo.content'], errors='replace')
 				try:
 					rmt_idx.readHeader(f_dec)
-					remote_timestamp = rmt_idx.header.get("TIMESTAMP", None)
+					if not remote_timestamp: # in case it had not been read from HTTP header
+						remote_timestamp = rmt_idx.header.get("TIMESTAMP", None)
 					if not remote_timestamp:
 						# no timestamp in the header, something's wrong
 						pkgindex = None
@@ -931,6 +943,12 @@ class binarytree(object):
 						writemsg("\n\n!!! %s\n" % \
 							_("Timed out while closing connection to binhost"),
 							noiselevel=-1)
+			except UseCachedCopyOfRemoteIndex:
+				writemsg_stdout("\n")
+				writemsg_stdout(
+					colorize("GOOD", _("Local copy of remote index is up-to-date and will be used.")) + \
+					"\n")
+				rmt_idx = pkgindex
 			except EnvironmentError as e:
 				writemsg(_("\n\n!!! Error fetching binhost package" \
 					" info from '%s'\n") % _hide_url_passwd(base_url))
diff --git a/pym/portage/util/_urlopen.py b/pym/portage/util/_urlopen.py
index 307624bc4..42961883d 100644
--- a/pym/portage/util/_urlopen.py
+++ b/pym/portage/util/_urlopen.py
@@ -2,6 +2,9 @@
 # Distributed under the terms of the GNU General Public License v2
 
 import sys
+from datetime import datetime
+from time import mktime
+from email.utils import formatdate, parsedate
 
 try:
 	from urllib.request import urlopen as _urlopen
@@ -14,15 +17,39 @@ except ImportError:
 	import urllib2 as urllib_request
 	from urllib import splituser as urllib_parse_splituser
 
-def urlopen(url):
+if sys.hexversion >= 0x3000000:
+	long = int
+
+# to account for the difference between TIMESTAMP of the index' contents
+#  and the file-'mtime'
+TIMESTAMP_TOLERANCE=5
+
+def urlopen(url, if_modified_since=None):
+	parse_result = urllib_parse.urlparse(url)
 	try:
-		return _urlopen(url)
+		if parse_result.scheme not in ("http", "https"):
+			return _urlopen(url)
+		request = urllib_request.Request(url)
+		request.add_header('User-Agent', 'Gentoo Portage')
+		if if_modified_since:
+			request.add_header('If-Modified-Since', _timestamp_to_http(if_modified_since))
+		opener = urllib_request.build_opener()
+		hdl = opener.open(request)
+		if hdl.headers.get('last-modified', ''):
+			try:
+				add_header = hdl.headers.add_header
+			except AttributeError:
+				# Python 2
+				add_header = hdl.headers.addheader
+			add_header('timestamp', _http_to_timestamp(hdl.headers.get('last-modified')))
+		return hdl
 	except SystemExit:
 		raise
-	except Exception:
+	except Exception as e:
+		if hasattr(e, 'code') and e.code == 304: # HTTPError 304: not modified
+			raise
 		if sys.hexversion < 0x3000000:
 			raise
-		parse_result = urllib_parse.urlparse(url)
 		if parse_result.scheme not in ("http", "https") or \
 			not parse_result.username:
 			raise
@@ -40,3 +67,13 @@ def _new_urlopen(url):
 	auth_handler = urllib_request.HTTPBasicAuthHandler(password_manager)
 	opener = urllib_request.build_opener(auth_handler)
 	return opener.open(url)
+
+def _timestamp_to_http(timestamp):
+	dt = datetime.fromtimestamp(float(long(timestamp)+TIMESTAMP_TOLERANCE))
+	stamp = mktime(dt.timetuple())
+	return formatdate(timeval=stamp, localtime=False, usegmt=True)
+
+def _http_to_timestamp(http_datetime_string):
+	tuple = parsedate(http_datetime_string)
+	timestamp = mktime(tuple)
+	return str(long(timestamp))