Allow convenient filtering of metric descriptors by type prefix.

gcloud/monitoring/client.py

@@ -131,26 +131,36 @@ def fetch_metric_descriptor(self, metric_type):
         """
         return MetricDescriptor._fetch(self, metric_type)
 
-    def list_metric_descriptors(self, filter_string=None):
+    def list_metric_descriptors(self, filter_string=None, type_prefix=None):
         """List all metric descriptors for the project.
 
-        Example::
+        Examples::
 
             >>> for descriptor in client.list_metric_descriptors():
             ...     print(descriptor.type)
 
+            >>> for descriptor in client.list_metric_descriptors(
+            ...         type_prefix='custom.'):
+            ...     print(descriptor.type)
+
         :type filter_string: string or None
         :param filter_string:
             An optional filter expression describing the metric descriptors
             to be returned. See the `filter documentation`_.
 
+        :type type_prefix: string or None
+        :param type_prefix: An optional prefix constraining the selected
+            metric types. This adds ``metric.type = starts_with("<prefix>")``
+            to the filter.
+
         :rtype: list of :class:`~gcloud.monitoring.metric.MetricDescriptor`
         :returns: A list of metric descriptor instances.
 
         .. _filter documentation:
             https://cloud.google.com/monitoring/api/v3/filters
         """
-        return MetricDescriptor._list(self, filter_string)
+        return MetricDescriptor._list(self, filter_string,
+                                      type_prefix=type_prefix)
 
     def fetch_resource_descriptor(self, resource_type):
         """Look up a resource descriptor by type.

gcloud/monitoring/metric.py

@@ -132,7 +132,7 @@ def _fetch(cls, client, metric_type):
         return cls._from_dict(info)
 
     @classmethod
-    def _list(cls, client, filter_string=None):
+    def _list(cls, client, filter_string=None, type_prefix=None):
         """List all metric descriptors for the project.
 
         :type client: :class:`gcloud.monitoring.client.Client`
@@ -143,6 +143,11 @@ def _list(cls, client, filter_string=None):
             An optional filter expression describing the metric descriptors
             to be returned. See the `filter documentation`_.
 
+        :type type_prefix: string or None
+        :param type_prefix: An optional prefix constraining the selected
+            metric types. This adds ``metric.type = starts_with("<prefix>")``
+            to the filter.
+
         :rtype: list of :class:`MetricDescriptor`
         :returns: A list of metric descriptor instances.
 
@@ -152,14 +157,21 @@ def _list(cls, client, filter_string=None):
         path = '/projects/{project}/metricDescriptors/'.format(
             project=client.project)
 
-        descriptors = []
+        filters = []
+        if filter_string is not None:
+            filters.append(filter_string)
 
+        if type_prefix is not None:
+            filters.append('metric.type = starts_with("{prefix}")'.format(
+                prefix=type_prefix))
+
+        descriptors = []
         page_token = None
         while True:
             params = {}
 
-            if filter_string is not None:
-                params['filter'] = filter_string
+            if filters:
+                params['filter'] = ' AND '.join(filters)
 
             if page_token is not None:
                 params['pageToken'] = page_token

gcloud/monitoring/test_metric.py

@@ -321,6 +321,28 @@ def test_list_filtered(self):
                             'query_params': {'filter': FILTER}}
         self.assertEqual(request, expected_request)
 
+    def test_list_filtered_by_type_prefix(self):
+        PROJECT = 'my-project'
+        PATH = 'projects/{project}/metricDescriptors/'.format(project=PROJECT)
+
+        # Request only custom metrics.
+        PREFIX = 'custom.googleapis.com/'
+        FILTER = 'metric.type = starts_with("{prefix}")'.format(prefix=PREFIX)
+
+        # But let's say there are no custom metrics.
+        RESPONSE = {'metricDescriptors': []}
+
+        connection = _Connection(RESPONSE)
+        client = _Client(project=PROJECT, connection=connection)
+        descriptors = self._getTargetClass()._list(client, type_prefix=PREFIX)
+
+        self.assertEqual(len(descriptors), 0)
+
+        request, = connection._requested
+        expected_request = {'method': 'GET', 'path': '/' + PATH,
+                            'query_params': {'filter': FILTER}}
+        self.assertEqual(request, expected_request)
+
 
 class TestMetric(unittest2.TestCase):
 

system_tests/monitoring.py

@@ -79,6 +79,18 @@ def test_list_metric_descriptors(self):
             self.assertTrue(label.value_type)
             self.assertTrue(label.description)
 
+    def test_list_metric_descriptors_filtered(self):
+        client = monitoring.Client()
+
+        PREFIX = 'compute.googleapis.com/'
+        descriptors = client.list_metric_descriptors(type_prefix=PREFIX)
+
+        # There are currently 18 types with this prefix, but that may change.
+        self.assertGreater(len(descriptors), 10)
+
+        for descriptor in descriptors:
+            self.assertTrue(descriptor.type.startswith(PREFIX))
+
     def test_fetch_resource_descriptor(self):
         client = monitoring.Client()
         descriptor = client.fetch_resource_descriptor(RESOURCE_TYPE)