Add get_label_values function in prometheus_connect.py. (#235)

* Add get_label_values function in prometheus_connect.py.

* Improving the all_metrics function via get_label_values.

* Added tests for get_label_values().

Co-authored-by: Alexey Sergeev <alexey.sergeev@nordigy.ru>

Author: lixir

prometheus_api_client/prometheus_connect.py

@@ -91,21 +91,36 @@ def all_metrics(self, params: dict = None):
             (RequestException) Raises an exception in case of a connection error
             (PrometheusApiClientException) Raises in case of non 200 response status code
         """
+        self._all_metrics = self.get_label_values(label_name="__name__", params=params)
+        return self._all_metrics
+
+    def get_label_values(self, label_name: str, params: dict = None):
+        """
+        Get a list of all values for the label.
+
+        :param label_name: (str) The name of the label for which you want to get all the values.
+        :param params: (dict) Optional dictionary containing GET parameters to be
+            sent along with the API request, such as "time"
+        :returns: (list) A list of names for the label from the specified prometheus host
+        :raises:
+            (RequestException) Raises an exception in case of a connection error
+            (PrometheusApiClientException) Raises in case of non 200 response status code
+        """
         params = params or {}
         response = self._session.get(
-            "{0}/api/v1/label/__name__/values".format(self.url),
+            "{0}/api/v1/label/{1}/values".format(self.url, label_name),
             verify=self.ssl_verification,
             headers=self.headers,
             params=params,
         )
 
         if response.status_code == 200:
-            self._all_metrics = response.json()["data"]
+            labels = response.json()["data"]
         else:
             raise PrometheusApiClientException(
                 "HTTP Status Code {} ({!r})".format(response.status_code, response.content)
             )
-        return self._all_metrics
+        return labels
 
     def get_current_metric_value(
         self, metric_name: str, label_config: dict = None, params: dict = None

tests/test_prometheus_connect.py

@@ -23,6 +23,11 @@ def test_metrics_list(self):
         """Check if setup was done correctly."""
         metrics_list = self.pc.all_metrics()
         self.assertTrue(len(metrics_list) > 0, "no metrics received from prometheus")
+        # Checking that the results of all_metrics() and get_label_values("__name__") are the same.
+        self.assertEqual(metrics_list, self.pc.get_label_values("__name__"))
+        # Check for the "job" label.
+        label_values = self.pc.get_label_values("job")
+        self.assertTrue(len(label_values) > 0, "no metrics received from prometheus")
 
     def test_get_metric_range_data(self):  # noqa D102
         start_time = datetime.now() - timedelta(minutes=10)
@@ -159,11 +164,20 @@ def test_unauthorized(self):  # noqa D102
                 self.pc.all_metrics()
         self.assertEqual("HTTP Status Code 403 (b'Unauthorized')", str(exc.exception))
 
+        with self.mock_response("Unauthorized", status_code=403):
+            with self.assertRaises(PrometheusApiClientException) as exc:
+                self.pc.get_label_values("label_name")
+        self.assertEqual("HTTP Status Code 403 (b'Unauthorized')", str(exc.exception))
+
     def test_broken_responses(self):  # noqa D102
         with self.assertRaises(PrometheusApiClientException) as exc:
             self.pc.all_metrics()
         self.assertEqual("HTTP Status Code 403 (b'BOOM!')", str(exc.exception))
 
+        with self.assertRaises(PrometheusApiClientException) as exc:
+            self.pc.get_label_values("label_name")
+        self.assertEqual("HTTP Status Code 403 (b'BOOM!')", str(exc.exception))
+
         with self.assertRaises(PrometheusApiClientException) as exc:
             self.pc.get_current_metric_value("metric")
         self.assertEqual("HTTP Status Code 403 (b'BOOM!')", str(exc.exception))
@@ -196,3 +210,12 @@ def test_all_metrics_method(self):  # noqa D102
             self.assertEqual(handler.call_count, 1)
             request = handler.requests[0]
             self.assertEqual(request.path_url, "/api/v1/label/__name__/values")
+
+    def test_get_label_values_method(self):  # noqa D102
+        all_metrics_payload = {"status": "success", "data": ["value1", "value2"]}
+
+        with self.mock_response(all_metrics_payload) as handler:
+            self.assertTrue(len(self.pc.get_label_values("label_name")))
+            self.assertEqual(handler.call_count, 1)
+            request = handler.requests[0]
+            self.assertEqual(request.path_url, "/api/v1/label/label_name/values")