Add label-list webapp endpoint

This is useful for getting the list of all available labels.
Originally implemented in Iafff02d546abb34affa88310f6a97918166cbf47,
this is based on the new info available from
Icfb73fbe3b67321235a78ea7ed9bf4319567eb1a

Co-Authored-By: Tristan Cacqueray <tdecacqu@redhat.com>
Change-Id: I4b43ac0e2ba44516ff289e93dbf553033fc9e130
Depends-On: https://review.openstack.org/548376

doc/source/operation.rst

@@ -263,3 +263,12 @@ launchers, all will provide the same information.
    :reqheader Accept: ``application/json`` or ``text/*``
    :resheader Content-Type: ``application/json`` or ``text/plain``
                             depending on the :http:header:`Accept` header
+
+.. http:get:: /label-list
+
+   All available labels as reported by all launchers
+
+   :query fields: comma-separated list of fields to display
+   :reqheader Accept: ``application/json`` or ``text/*``
+   :resheader Content-Type: ``application/json`` or ``text/plain``
+                            depending on the :http:header:`Accept` header

nodepool/status.py

@@ -244,3 +244,24 @@ def request_list(zk):
         objs.append(dict(zip(headers_table.keys(),
                              values)))
     return (objs, headers_table)
+
+
+def label_list(zk):
+    headers_table = OrderedDict([
+        ("label", "Label"),
+    ])
+    objs = []
+
+    # Walk all launchers, find the labels they support and stick it
+    # all in a set.
+    # NOTE(ianw): maybe add to each entry a list of which
+    #             launchers support the label?
+    labels = set()
+    launchers = zk.getRegisteredLaunchers()
+    for launcher in launchers:
+        labels.update(launcher.supported_labels)
+
+    for label in labels:
+        objs.append({'label': label})
+
+    return (objs, headers_table)

nodepool/tests/test_webapp.py

@@ -206,6 +206,28 @@ class TestWebApp(tests.DBTestCase):
                                        'requestor': 'test_request_list', },
                                       objs[0])
 
+    def test_label_list_json(self):
+        configfile = self.setup_config('node.yaml')
+        pool = self.useNodepool(configfile, watermark_sleep=1)
+        self.useBuilder(configfile)
+        pool.start()
+        webapp = self.useWebApp(pool, port=0)
+        webapp.start()
+        port = webapp.server.socket.getsockname()[1]
+
+        self.waitForImage('fake-provider', 'fake-image')
+        self.waitForNodes('fake-label')
+
+        req = request.Request(
+            "http://localhost:%s/label-list" % port)
+        req.add_header('Accept', 'application/json')
+        f = request.urlopen(req)
+        self.assertEqual(f.info().get('Content-Type'),
+                         'application/json')
+        data = f.read()
+        objs = json.loads(data.decode('utf8'))
+        self.assertEqual([{'label': 'fake-label'}], objs)
+
     def test_webapp_config(self):
         configfile = self.setup_config('webapp.yaml')
         config = yaml.safe_load(open(configfile))

nodepool/webapp.py

@@ -99,6 +99,8 @@ class WebApp(threading.Thread):
                                        node_id=params.get('node_id'))
         elif path == '/request-list':
             results = status.request_list(zk)
+        elif path == '/label-list':
+            results = status.label_list(zk)
         else:
             return None