Add prometheus data source for watcher decision engine

This adds a new data source for the Watcher decision engine that
implements the watcher.decision_engine.datasources.DataSourceBase.

related spec was merged at [1].

Implements: blueprint prometheus-datasource

[1] https://review.opendev.org/c/openstack/watcher-specs/+/933300

Change-Id: I6a70c4acc70a864c418cf347f5f6951cb92ec906

watcher/conf/__init__.py

@@ -42,6 +42,7 @@ from watcher.conf import nova_client
 from watcher.conf import paths
 from watcher.conf import placement_client
 from watcher.conf import planner
+from watcher.conf import prometheus_client
 from watcher.conf import service
 
 CONF = cfg.CONF
@@ -70,3 +71,4 @@ clients_auth.register_opts(CONF)
 ironic_client.register_opts(CONF)
 collector.register_opts(CONF)
 placement_client.register_opts(CONF)
+prometheus_client.register_opts(CONF)

watcher/conf/prometheus_client.py

@@ -0,0 +1,58 @@
+# Copyright 2024 Red Hat, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+
+from oslo_config import cfg
+
+prometheus_client = cfg.OptGroup(name='prometheus_client',
+                                 title='Configuration Options for Prometheus',
+                                 help="See https://docs.openstack.org/watcher/"
+                                      "latest/datasources/prometheus.html for "
+                                      "details on how these options are used.")
+
+PROMETHEUS_CLIENT_OPTS = [
+    cfg.StrOpt('host',
+               help="The hostname or IP address for the prometheus server."),
+    cfg.StrOpt('port',
+               help="The port number used by the prometheus server."),
+    cfg.StrOpt('fqdn_label',
+               default="fqdn",
+               help="The label that Prometheus uses to store the fqdn of "
+                    "exporters. Defaults to 'fqdn'."),
+    cfg.StrOpt('username',
+               help="The basic_auth username to use to authenticate with the "
+                    "Prometheus server."),
+    cfg.StrOpt('password',
+               secret=True,
+               help="The basic_auth password to use to authenticate with the "
+                    "Prometheus server."),
+    cfg.StrOpt('cafile',
+               help="Path to the CA certificate for establishing a TLS "
+                    "connection with the Prometheus server."),
+    cfg.StrOpt('certfile',
+               help="Path to the client certificate for establishing a TLS "
+                    "connection with the Prometheus server."),
+    cfg.StrOpt('keyfile',
+               help="Path to the client key for establishing a TLS "
+                    "connection with the Prometheus server."),
+]
+
+
+def register_opts(conf):
+    conf.register_group(prometheus_client)
+    conf.register_opts(PROMETHEUS_CLIENT_OPTS, group=prometheus_client)
+
+
+def list_opts():
+    return [(prometheus_client, PROMETHEUS_CLIENT_OPTS)]