googleapis · dhermes · Jan 29, 2015 · Feb 5, 2015
diff --git a/gcloud/__init__.py b/gcloud/__init__.py
@@ -16,4 +16,89 @@
 
 from pkg_resources import get_distribution
 
+import six
+import socket
+
+try:
+    from google import appengine
+except ImportError:
+    appengine = None
+
+
 __version__ = get_distribution('gcloud').version
+
+
+HTTPConnection = six.moves.http_client.HTTPConnection
+
+
+class _UserAgentReifyProperty(object):
+    """Helper for extra environment information."""
+
+    _curr_environ = None
+    _user_agent = None
+
+    def __init__(self, wrapped):
+        self._property_name = wrapped.__name__
+        self._curr_environ = self.environ_at_init()
+
+    @staticmethod
+    def environ_at_init():
+        """Checks environment variables during instance initialization.
+
+        Intended to infer as much as possible from the environment without
+        running code.
+
+        :rtype: string or ``NoneType``
+        :returns: Either ``'-GAE'`` if on App Engine else ``None``
+        """
+        if appengine is not None:
+            return '-GAE'
+
+    def environ_post_init(self):
+        """Checks environment variables after instance initialization.
+
+        This is meant for checks which can't be performed instantaneously.
+
+        :rtype: string
+        :returns: Either ``'-GCE'`` if on Compute Engine else an empty string.
+        """
+        gce_environ = self.check_compute_engine()
+        if gce_environ is not None:
+            return gce_environ
+
+        return ''
+
+    @staticmethod
+    def check_compute_engine():
+        """Checks if the current environment is Compute Engine.
+
+        :rtype: string or ``NoneType``
+        :returns: The string ``'-GCE'`` if on Compute Engine else ``None``.
+        """
+        host = '169.254.169.254'
+        uri_path = '/computeMetadata/v1/project/project-id'
+        headers = {'Metadata-Flavor': 'Google'}
+        connection = HTTPConnection(host, timeout=0.1)
+        try:
+            connection.request('GET', uri_path, headers=headers)
+            response = connection.getresponse()
+            if response.status == 200:
+                return '-GCE'
+        except socket.error:  # Expect timeout or host is down
+            pass
+        finally:
+            connection.close()
+
+    def __get__(self, inst, objtype=None):
+        if inst is None:
+            return self
+
+        if self._curr_environ is None:
+            self._curr_environ = self.environ_post_init()
+
+        if self._user_agent is None:
+            self._user_agent = "gcloud-python/{0}{1}".format(
+                __version__, self._curr_environ)
+
+        setattr(inst, self._property_name, self._user_agent)
+        return self._user_agent
diff --git a/gcloud/connection.py b/gcloud/connection.py
@@ -14,10 +14,10 @@
 
 """ Shared implementation of connections to API servers."""
 
-from pkg_resources import get_distribution
-
 import httplib2
 
+import gcloud
+
 
 class Connection(object):
     """A generic connection to Google Cloud Platform.
@@ -29,12 +29,6 @@ class Connection(object):
     API_BASE_URL = 'https://www.googleapis.com'
     """The base of the API call URL."""
 
-    _EMPTY = object()
-    """A pointer to represent an empty value for default arguments."""
-
-    USER_AGENT = "gcloud-python/{0}".format(get_distribution('gcloud').version)
-    """The user agent for gcloud-python requests."""
-
     def __init__(self, credentials=None):
         """Constructor for Connection.
 
@@ -45,6 +39,11 @@ def __init__(self, credentials=None):
         self._http = None
         self._credentials = credentials
 
+    @gcloud._UserAgentReifyProperty  # pragma: NO COVER
+    def user_agent(self):
+        """The user agent for gcloud-python requests."""
+        # The decorator will handle the value.
+
     @property
     def credentials(self):
         """Getter for current credentials.

diff --git a/gcloud/datastore/connection.py b/gcloud/datastore/connection.py
@@ -59,7 +59,7 @@ def _request(self, dataset_id, method, data):
         headers = {
             'Content-Type': 'application/x-protobuf',
             'Content-Length': str(len(data)),
-            'User-Agent': self.USER_AGENT,
+            'User-Agent': self.user_agent,
         }
         headers, content = self.http.request(
             uri=self.build_api_url(dataset_id=dataset_id, method=method),

diff --git a/gcloud/datastore/test_api.py b/gcloud/datastore/test_api.py
@@ -300,7 +300,7 @@ def _verifyProtobufCall(self, called_with, URI, conn):
         self.assertEqual(called_with['headers']['Content-Type'],
                          'application/x-protobuf')
         self.assertEqual(called_with['headers']['User-Agent'],
-                         conn.USER_AGENT)
+                         conn.user_agent)
 
     def test_w_deferred_from_backend_but_not_passed(self):
         from gcloud.datastore import _datastore_v1_pb2 as datastore_pb

diff --git a/gcloud/datastore/test_connection.py b/gcloud/datastore/test_connection.py
@@ -36,15 +36,18 @@ def _make_query_pb(self, kind):
         return pb
 
     def _makeOne(self, *args, **kw):
-        return self._getTargetClass()(*args, **kw)
+        conn = self._getTargetClass()(*args, **kw)
+        # Set the user agent so the user_agent is not lazily loaded.
+        setattr(conn, 'user_agent', 'gcloud-python/test')
+        return conn
 
     def _verifyProtobufCall(self, called_with, URI, conn):
         self.assertEqual(called_with['uri'], URI)
         self.assertEqual(called_with['method'], 'POST')
         self.assertEqual(called_with['headers']['Content-Type'],
                          'application/x-protobuf')
         self.assertEqual(called_with['headers']['User-Agent'],
-                         conn.USER_AGENT)
+                         conn.user_agent)
 
     def test_ctor_defaults(self):
         conn = self._makeOne()
@@ -409,7 +412,7 @@ def test_lookup_multiple_keys_w_deferred(self):
         self.assertEqual(cw['method'], 'POST')
         self.assertEqual(cw['headers']['Content-Type'],
                          'application/x-protobuf')
-        self.assertEqual(cw['headers']['User-Agent'], conn.USER_AGENT)
+        self.assertEqual(cw['headers']['User-Agent'], conn.user_agent)
         rq_class = datastore_pb.LookupRequest
         request = rq_class()
         request.ParseFromString(cw['body'])

diff --git a/gcloud/storage/blob.py b/gcloud/storage/blob.py
@@ -300,7 +300,7 @@ def upload_from_file(self, file_obj, rewind=False, size=None,
         headers = {
             'Accept': 'application/json',
             'Accept-Encoding': 'gzip, deflate',
-            'User-Agent': conn.USER_AGENT,
+            'User-Agent': conn.user_agent,
         }
 
         upload = transfer.Upload(file_obj,

diff --git a/gcloud/storage/connection.py b/gcloud/storage/connection.py
@@ -169,7 +169,7 @@ def make_request(self, method, url, data=None, content_type=None,
         if content_type:
             headers['Content-Type'] = content_type
 
-        headers['User-Agent'] = self.USER_AGENT
+        headers['User-Agent'] = self.user_agent
 
         return self.http.request(uri=url, method=method, headers=headers,
                                  body=data)

diff --git a/gcloud/storage/test_blob.py b/gcloud/storage/test_blob.py
@@ -904,11 +904,11 @@ def _respond(self, **kw):
 class _Connection(_Responder):
 
     API_BASE_URL = 'http://example.com'
-    USER_AGENT = 'testing 1.2.3'
     credentials = object()
 
     def __init__(self, *responses):
         super(_Connection, self).__init__(*responses)
+        self.user_agent = 'testing 1.2.3'
         self._signed = []
         self.http = _HTTP(*responses)
 

diff --git a/gcloud/storage/test_connection.py b/gcloud/storage/test_connection.py
@@ -22,7 +22,10 @@ def _getTargetClass(self):
         return Connection
 
     def _makeOne(self, *args, **kw):
-        return self._getTargetClass()(*args, **kw)
+        conn = self._getTargetClass()(*args, **kw)
+        # Set the user agent so the user_agent is not lazily loaded.
+        setattr(conn, 'user_agent', 'gcloud-python/test')
+        return conn
 
     def test_ctor_defaults(self):
         PROJECT = 'project'
@@ -194,7 +197,7 @@ def test_make_request_no_data_no_content_type_no_headers(self):
         expected_headers = {
             'Accept-Encoding': 'gzip',
             'Content-Length': 0,
-            'User-Agent': conn.USER_AGENT,
+            'User-Agent': conn.user_agent,
         }
         self.assertEqual(http._called_with['headers'], expected_headers)
 
@@ -214,7 +217,7 @@ def test_make_request_w_data_no_extra_headers(self):
             'Accept-Encoding': 'gzip',
             'Content-Length': 0,
             'Content-Type': 'application/json',
-            'User-Agent': conn.USER_AGENT,
+            'User-Agent': conn.user_agent,
         }
         self.assertEqual(http._called_with['headers'], expected_headers)
 
@@ -234,7 +237,7 @@ def test_make_request_w_extra_headers(self):
             'Accept-Encoding': 'gzip',
             'Content-Length': 0,
             'X-Foo': 'foo',
-            'User-Agent': conn.USER_AGENT,
+            'User-Agent': conn.user_agent,
         }
         self.assertEqual(http._called_with['headers'], expected_headers)
 
@@ -258,7 +261,7 @@ def test_api_request_defaults(self):
         expected_headers = {
             'Accept-Encoding': 'gzip',
             'Content-Length': 0,
-            'User-Agent': conn.USER_AGENT,
+            'User-Agent': conn.user_agent,
         }
         self.assertEqual(http._called_with['headers'], expected_headers)
 
@@ -305,7 +308,7 @@ def test_api_request_w_query_params(self):
         expected_headers = {
             'Accept-Encoding': 'gzip',
             'Content-Length': 0,
-            'User-Agent': conn.USER_AGENT,
+            'User-Agent': conn.user_agent,
         }
         self.assertEqual(http._called_with['headers'], expected_headers)
 
@@ -333,7 +336,7 @@ def test_api_request_w_data(self):
             'Accept-Encoding': 'gzip',
             'Content-Length': len(DATAJ),
             'Content-Type': 'application/json',
-            'User-Agent': conn.USER_AGENT,
+            'User-Agent': conn.user_agent,
         }
         self.assertEqual(http._called_with['headers'], expected_headers)