Provide a RFC 7231 compliant user agent string

The current default of "keystoneauth1" doesn't convey enough
information, and additionally when the user of a Session supplies their
own user agent, it stomps on any notion of keystoneauth1 being there.

Per RFC 7231 Section 5.5.3
(https://tools.ietf.org/html/rfc7231#section-5.5.3), user agents should
basically be a space-delimited list of product/version pairs in
decreasing order of importance. This change makes the default user agent
something like the following:

keystoneauth1/2.1.1 python-requests/2.8.1 CPython/3.4.1+

Due to the decreasing order of importance, when a user creates a Session
with something like Session(user_agent="my-product/1.0"),
'my-product/1.0' is then prepended to the above list. The only time this
is not the case is if a user agent is provided directly to
Session.request. In that case, the User-Agent header is set to whatever
the provided argument is, verbatim.

This was a change we had originally made to the Transport class in
python-openstacksdk (I80ca26fff3f2522b8232472676396abb86166f91), but
upon moving to keystoneauth instead of our own implementation, it was
noticed that we lost this, and keystoneauth is a better place for this
than for us to re-implement it inside of python-openstacksdk.

Change-Id: I46f336f25fac5b524547bb13e4f5438ebf1d4320

keystoneauth1/__init__.py

@@ -0,0 +1,16 @@
+# 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 pbr.version
+
+
+__version__ = pbr.version.VersionInfo('keystoneauth1').version_string()

keystoneauth1/session.py

@@ -15,6 +15,7 @@ import functools
 import hashlib
 import json
 import logging
+import platform
 import socket
 import time
 import uuid
@@ -23,6 +24,7 @@ import requests
 import six
 from six.moves import urllib
 
+import keystoneauth1
 from keystoneauth1 import _utils as utils
 from keystoneauth1 import exceptions
 
@@ -36,7 +38,9 @@ try:
 except ImportError:
     osprofiler_web = None
 
-USER_AGENT = 'keystoneauth1'
+DEFAULT_USER_AGENT = 'keystoneauth1/%s %s %s/%s' % (
+    keystoneauth1.__version__, requests.utils.default_user_agent(),
+    platform.python_implementation(), platform.python_version())
 
 _logger = utils.get_logger(__name__)
 
@@ -95,8 +99,12 @@ class Session(object):
                           of seconds or 0 for no timeout. (optional, defaults
                           to 0)
     :param string user_agent: A User-Agent header string to use for the
-                              request. If not provided a default is used.
+                              request. If not provided, a default of
-                              (optional, defaults to 'keystoneauth1')
+                              :attr:`~keystoneauth1.session.DEFAULT_USER_AGENT`
+                              is used, which contains the keystoneauth1 version
+                              as well as those of the requests library and
+                              which Python is being used. When a non-None value
+                              is passed, it will be prepended to the default.
     :param int/bool redirect: Controls the maximum number of redirections that
                               can be followed by a request. Either an integer
                               for a specific count or True/False for
@@ -127,7 +135,11 @@ class Session(object):
 
         # don't override the class variable if none provided
         if user_agent is not None:
-            self.user_agent = user_agent
+            # Per RFC 7231 Section 5.5.3, identifiers in a user-agent
+            # should be ordered by decreasing significance.
+            # If a user sets their product, we prepend it to the KSA
+            # version, requests version, and then the Python version.
+            self.user_agent = "%s %s" % (user_agent, DEFAULT_USER_AGENT)
 
         self._json = _JSONEncoder()
 
@@ -367,7 +379,7 @@ class Session(object):
         elif self.user_agent:
             user_agent = headers.setdefault('User-Agent', self.user_agent)
         else:
-            user_agent = headers.setdefault('User-Agent', USER_AGENT)
+            user_agent = headers.setdefault('User-Agent', DEFAULT_USER_AGENT)
 
         if self.original_ip:
             headers.setdefault('Forwarded',

keystoneauth1/tests/unit/test_session.py

@@ -89,12 +89,15 @@ class SessionTests(utils.TestCase):
         self.assertRequestBodyIs(json={'hello': 'world'})
 
     def test_user_agent(self):
-        session = client_session.Session(user_agent='test-agent')
+        custom_agent = 'custom-agent/1.0'
+        session = client_session.Session(user_agent=custom_agent)
         self.stub_url('GET', text='response')
         resp = session.get(self.TEST_URL)
 
         self.assertTrue(resp.ok)
-        self.assertRequestHeaderEqual('User-Agent', 'test-agent')
+        self.assertRequestHeaderEqual(
+            'User-Agent',
+            '%s %s' % (custom_agent, client_session.DEFAULT_USER_AGENT))
 
         resp = session.get(self.TEST_URL, headers={'User-Agent': 'new-agent'})
         self.assertTrue(resp.ok)

requirements.txt

@@ -2,6 +2,7 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 
+pbr>=1.6
 argparse
 iso8601>=0.1.9
 requests>=2.8.1