static method to get_highest_client_server_version

This method takes a url for the cinder server endpoint and queries
the server for version info. It then returns the min of the server's
highest supported version and the cinderclients MAX_VERSION.

Change-Id: Ifb3478f1dba660a5d75d243dc2aaf6b421940752

cinderclient/client.py

@@ -97,6 +97,13 @@ def get_server_version(url):
         return api_versions.APIVersion("2.0"), api_versions.APIVersion("2.0")
 
 
+def get_highest_client_server_version(url):
+    min_server, max_server = get_server_version(url)
+    max_server_version = api_versions.APIVersion.get_string(max_server)
+
+    return min(float(max_server_version), float(api_versions.MAX_VERSION))
+
+
 def get_volume_api_from_url(url):
     scheme, netloc, path, query, frag = urlparse.urlsplit(url)
     components = path.split("/")

cinderclient/tests/unit/test_client.py

@@ -332,3 +332,22 @@ class GetAPIVersionTestCase(utils.TestCase):
         min_version, max_version = cinderclient.client.get_server_version(url)
         self.assertEqual(min_version, api_versions.APIVersion('3.0'))
         self.assertEqual(max_version, api_versions.APIVersion('3.16'))
+
+    @mock.patch('cinderclient.client.requests.get')
+    def test_get_highest_client_server_version(self, mock_request):
+
+        mock_response = utils.TestResponse({
+            "status_code": 200,
+            "text": json.dumps(fakes.fake_request_get())
+        })
+
+        mock_request.return_value = mock_response
+
+        url = "http://192.168.122.127:8776/v3/e5526285ebd741b1819393f772f11fc3"
+
+        highest = cinderclient.client.get_highest_client_server_version(url)
+        current_client_MAX_VERSION = float(api_versions.MAX_VERSION)
+        if current_client_MAX_VERSION > 3.16:
+            self.assertEqual(3.16, highest)
+        else:
+            self.assertEqual(current_client_MAX_VERSION, highest)