Add support for group trigger deletion in hawkular alerts

Adding delete_group_trigger method in hawkular alerts and
test_delete_group_trigger to alerts tests.

Since the `DELETE` action returns only a response code, without body,
I added `parse_json` flag to `_http` method in `hawkular/client.py`.
Without this addition an error is raised when trying to load
the json with no content. I'm setting it to `True` by default,
while sending it with `False` from the `_delete` method.
This Issue was solved in `hawkular/metrics.py` by checking that the
method is `GET`, a wrong solution IMHO cause `POST` and `PUT` methods
also return body.

Author: dkorn

hawkular/alerts.py

@@ -155,6 +155,16 @@ def create_group_trigger(self, trigger):
         data = self._serialize_object(trigger)
         return Trigger(self._post(self._service_url(['triggers', 'groups']), data))
 
+    def delete_group_trigger(self, group_id, keep_non_orphans=False, keep_orphans=False):
+         """
+         Delete a group trigger
+         :param group_id: ID of the group trigger to delete
+         :param keep_non_orphans: if True converts the non-orphan member triggers to standard triggers
+         :param keep_orphans: if True converts the orphan member triggers to standard triggers
+         """
+         params = {'keepNonOrphans': str(keep_non_orphans).lower(), 'keepOrphans': str(keep_orphans).lower()}
+         self._delete(self._service_url(['triggers', 'groups', group_id], params=params))
+
     def create_group_member(self, member):
         data = self._serialize_object(member)
         return Trigger(self._post(self._service_url(['triggers', 'groups', 'members']), data))

hawkular/client.py

@@ -165,7 +165,7 @@ def _get_status_url(self):
     def tenant(self, tenant_id):
         self.tenant_id = tenant_id
 
-    def _http(self, url, method, data=None, decoder=None):
+    def _http(self, url, method, data=None, decoder=None, parse_json=True):
         res = None
         req = Request(url=url)
         req.add_header('Content-Type', 'application/json')
@@ -193,10 +193,13 @@ def _http(self, url, method, data=None, decoder=None):
             req.get_method = lambda: method
             res = urlopen(req, context=self.context)
 
-            if res.getcode() == 200:
-                data = json.load(reader(res), cls=decoder)
-            elif res.getcode() == 204:
-                data = {}
+            if parse_json:
+                if res.getcode() == 200:
+                    data = json.load(reader(res), cls=decoder)
+                elif res.getcode() == 204:
+                    data = {}
+            else:
+                data = reader(res).read()
 
             return data
 
@@ -211,7 +214,7 @@ def _put(self, url, data):
         return self._http(url, 'PUT', data)
 
     def _delete(self, url):
-        return self._http(url, 'DELETE')
+        return self._http(url, 'DELETE', parse_json=False)
 
     def _post(self, url, data):
         return self._http(url, 'POST', data)

tests/test_alerts.py

@@ -22,6 +22,13 @@
 import os
 from tests import base
 
+try:
+    # Python 3
+    from urllib.error import HTTPError
+except ImportError:
+    # Fall back to Python 2's urllib2
+    from urllib2 import HTTPError
+
 
 class TestAlertsFunctionsBase(unittest.TestCase):
     def setUp(self):
@@ -125,6 +132,23 @@ def test_create_group_trigger(self):
         self.assertEqual(created_group_trigger.id, trigger.id)
         self.assertEqual(created_group_trigger.name, trigger.name)
 
+    def test_delete_group_trigger(self):
+        # Create a group trigger
+        gt = Trigger()
+        gt.id = 'delete_group_trigger'
+        gt.name = 'group_trigger_to_delete'
+        self.client.create_group_trigger(gt)
+
+        group_count = len(self.client.list_triggers())
+        # Delete the created group trigger
+        self.client.delete_group_trigger('delete_group_trigger')
+
+        # Compare number of remaining triggers and query the deleted trigger id
+        self.assertEqual(len(self.client.list_triggers()), group_count-1)
+        with self.assertRaises(HTTPError) as e:
+            self.client.get_trigger('delete_group_trigger')
+            self.assertEqual(e.getcode(), 404)
+
     def test_create_groups(self):
         # Create a group trigger
         t = Trigger()