Add root_path configuration option

This allows to specify a root path to prepend each api call.

Change-Id: I033553809c72608388250d3ac66e17b5a2784e61

observabilityclient/prometheus_client.py

@@ -53,13 +53,18 @@ class PrometheusMetric(object):
 
 
 class PrometheusAPIClient(object):
-    def __init__(self, host, session=None):
+    def __init__(self, host, session=None, root_path=""):
         self._host = host
+        if not self._host.endswith('/'):
+            self._host += '/'
         if session is None:
             self._session = requests.Session()
         else:
             self._session = session
         self._session.verify = False
+        self._root_path = root_path
+        if root_path != "" and not self._root_path.endswith('/'):
+            self._root_path += '/'
 
     def set_ca_cert(self, ca_cert):
         self._session.verify = ca_cert
@@ -73,7 +78,7 @@ class PrometheusAPIClient(object):
 
     def _get_url(self, endpoint):
         scheme = 'https' if self._session.verify else 'http'
-        return f"{scheme}://{self._host}/api/v1/{endpoint}"  # noqa: E231
+        return f"{scheme}://{self._host}{self._root_path}api/v1/{endpoint}"
 
     def _get(self, endpoint, params=None):
         url = self._get_url(endpoint)

observabilityclient/tests/unit/test_prometheus_client.py

@@ -85,7 +85,8 @@ class PrometheusAPIClientTestBase(testtools.TestCase):
 class PrometheusAPIClientTest(PrometheusAPIClientTestBase):
     def test_get(self):
         url = "test"
-        expected_url = "http://localhost:9090/api/v1/test"
+        root_path = "root_path"
+        expected_url = f"http://localhost:9090/{root_path}/api/v1/{url}"
 
         params = {"query": "ceilometer_image_size{publisher='localhost'}"}
         expected_params = params
@@ -93,7 +94,8 @@ class PrometheusAPIClientTest(PrometheusAPIClientTestBase):
         return_value = self.GoodResponse()
         with mock.patch.object(requests.Session, 'get',
                                return_value=return_value) as m:
-            c = client.PrometheusAPIClient("localhost:9090")
+            c = client.PrometheusAPIClient("localhost:9090",
+                                           root_path=root_path)
             c._get(url, params)
 
         m.assert_called_with(expected_url,
@@ -121,7 +123,7 @@ class PrometheusAPIClientTest(PrometheusAPIClientTestBase):
 
     def test_post(self):
         url = "test"
-        expected_url = "http://localhost:9090/api/v1/test"
+        expected_url = f"http://localhost:9090/api/v1/{url}"
 
         params = {"query": "ceilometer_image_size{publisher='localhost'}"}
         expected_params = params

observabilityclient/tests/unit/test_utils.py

@@ -55,7 +55,7 @@ class GetPrometheusClientTest(testtools.TestCase):
                 mock.patch.object(prometheus_client.PrometheusAPIClient,
                                   "__init__", return_value=None) as m:
             metric_utils.get_prometheus_client()
-        m.assert_called_with("somehost:1234", None)
+        m.assert_called_with("somehost:1234", None, "")
 
     def test_get_prometheus_client_env_override(self):
         with mock.patch.dict(os.environ,
@@ -65,7 +65,7 @@ class GetPrometheusClientTest(testtools.TestCase):
                 mock.patch.object(prometheus_client.PrometheusAPIClient,
                                   "__init__", return_value=None) as m:
             metric_utils.get_prometheus_client()
-        m.assert_called_with("env_override:1234", None)
+        m.assert_called_with("env_override:1234", None, "")
 
     def test_get_prometheus_client_no_config_file(self):
         patched_env = {'PROMETHEUS_HOST': 'env_override',
@@ -76,7 +76,19 @@ class GetPrometheusClientTest(testtools.TestCase):
                 mock.patch.object(prometheus_client.PrometheusAPIClient,
                                   "__init__", return_value=None) as m:
             metric_utils.get_prometheus_client()
-        m.assert_called_with("env_override:env_port", None)
+        m.assert_called_with("env_override:env_port", None, "")
+
+    def test_get_prometheus_client_prefix_in_env_variable(self):
+        patched_env = {'PROMETHEUS_HOST': 'env_override',
+                       'PROMETHEUS_PORT': 'env_port',
+                       'PROMETHEUS_ROOT_PATH': 'root_path_env'}
+        with mock.patch.dict(os.environ, patched_env), \
+                mock.patch.object(metric_utils, 'get_config_file',
+                                  return_value=None), \
+                mock.patch.object(prometheus_client.PrometheusAPIClient,
+                                  "__init__", return_value=None) as m:
+            metric_utils.get_prometheus_client()
+        m.assert_called_with("env_override:env_port", None, "root_path_env")
 
     def test_get_prometheus_client_missing_configuration(self):
         with mock.patch.dict(os.environ, {}), \

observabilityclient/utils/metric_utils.py

@@ -49,6 +49,7 @@ def get_prometheus_client(session=None):
     host = None
     port = None
     ca_cert = None
+    root_path = ""
     conf_file = get_config_file()
     if conf_file is not None:
         conf = yaml.safe_load(conf_file)
@@ -58,6 +59,8 @@ def get_prometheus_client(session=None):
             port = conf['port']
         if 'ca_cert' in conf:
             ca_cert = conf['ca_cert']
+        if 'root_path' in conf:
+            root_path = conf['root_path']
         conf_file.close()
 
     # NOTE(jwysogla): We allow to overide the prometheus.yaml by
@@ -68,10 +71,12 @@ def get_prometheus_client(session=None):
         port = os.environ['PROMETHEUS_PORT']
     if 'PROMETHEUS_CA_CERT' in os.environ:
         ca_cert = os.environ['PROMETHEUS_CA_CERT']
+    if 'PROMETHEUS_ROOT_PATH' in os.environ:
+        root_path = os.environ['PROMETHEUS_ROOT_PATH']
     if host is None or port is None:
         raise ConfigurationError("Can't find prometheus host and "
                                  "port configuration.")
-    client = PrometheusAPIClient(f"{host}:{port}", session)  # noqa: E231
+    client = PrometheusAPIClient(f"{host}:{port}", session, root_path)
     if ca_cert is not None:
         client.set_ca_cert(ca_cert)
     return client

releasenotes/notes/add-root-path-192ac0e6ea99b84f.yaml

@@ -0,0 +1,9 @@
+---
+features:
+  - |
+    Added a "root_path" configuration option with a PROMETHEUS_ROOT_PATH
+    environment variable override, which allows to set a root path, which gets
+    prepended to the URL path section for each Prometheus API call. So for
+    example when Prometheus is hosted on localhost:80/prometheus, setting the
+    root_path to "prometheus" will enable the observabilityclient to send
+    requests to URLs like localhost:80/prometheus/api/v1/labels.