Add optional healthcheck middleware

This adds the healthcheck middleware from oslo, configurable via the
[healthcheck]/enabled option. This middleware adds a status check at
`/healthcheck`.

This is useful for load balancers to determine if a service is up (and
add or remove it from rotation), or for monitoring tools to see the
health of the server.

This endpoint is unauthenticated, as not all load balancers or
monitoring tools support authenticating with a health check endpoint.

Change-Id: I7929d5f4502c3f84b1cf30526c94a458081a6a29
Closes-Bug: #1748515

ironic/api/app.py

@@ -18,6 +18,7 @@
 import keystonemiddleware.audit as audit_middleware
 from oslo_config import cfg
 import oslo_middleware.cors as cors_middleware
+from oslo_middleware import healthcheck
 import osprofiler.web as osprofiler_web
 import pecan
 
@@ -103,6 +104,14 @@ def setup_app(pecan_config=None, extra_hooks=None):
     if CONF.profiler.enabled:
         app = osprofiler_web.WsgiMiddleware(app)
 
+    # add in the healthcheck middleware if enabled
+    # NOTE(jroll) this is after the auth token middleware as we don't want auth
+    # in front of this, and WSGI works from the outside in. Requests to
+    # /healthcheck will be handled and returned before the auth middleware
+    # is reached.
+    if CONF.healthcheck.enabled:
+        app = healthcheck.Healthcheck(app, CONF)
+
     # Create a CORS wrapper, and attach ironic-specific defaults that must be
     # included in all CORS responses.
     app = IronicCORS(app, CONF)

ironic/conf/__init__.py

@@ -29,6 +29,7 @@ from ironic.conf import deploy
 from ironic.conf import dhcp
 from ironic.conf import drac
 from ironic.conf import glance
+from ironic.conf import healthcheck
 from ironic.conf import ilo
 from ironic.conf import inspector
 from ironic.conf import ipmi
@@ -62,6 +63,7 @@ deploy.register_opts(CONF)
 drac.register_opts(CONF)
 dhcp.register_opts(CONF)
 glance.register_opts(CONF)
+healthcheck.register_opts(CONF)
 ilo.register_opts(CONF)
 inspector.register_opts(CONF)
 ipmi.register_opts(CONF)

ironic/conf/healthcheck.py

@@ -0,0 +1,29 @@
+#    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
+
+from ironic.common.i18n import _
+
+opts = [
+    cfg.BoolOpt('enabled',
+                default=False,
+                help=_('Enable the health check endpoint at /healthcheck. '
+                       'Note that this is unauthenticated. More information '
+                       'is available at '
+                       'https://docs.openstack.org/oslo.middleware/latest/'
+                       'reference/healthcheck_plugins.html.')),
+]
+
+
+def register_opts(conf):
+    conf.register_opts(opts, group='healthcheck')

ironic/conf/opts.py

@@ -47,6 +47,7 @@ _opts = [
     ('dhcp', ironic.conf.dhcp.opts),
     ('drac', ironic.conf.drac.opts),
     ('glance', ironic.conf.glance.list_opts()),
+    ('healthcheck', ironic.conf.healthcheck.opts),
     ('ilo', ironic.conf.ilo.opts),
     ('inspector', ironic.conf.inspector.list_opts()),
     ('ipmi', ironic.conf.ipmi.opts),

ironic/tests/unit/api/test_healthcheck.py

@@ -0,0 +1,39 @@
+#    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.
+"""
+Tests to assert that audit middleware works as expected.
+"""
+
+import mock
+from oslo_config import cfg
+from oslo_middleware import healthcheck
+
+from ironic.tests.unit.api import base
+
+
+CONF = cfg.CONF
+
+
+class TestHealthcheckMiddleware(base.BaseApiTest):
+    """Provide a basic smoke test to ensure healthcheck middleware works."""
+
+    @mock.patch.object(healthcheck, 'Healthcheck')
+    def test_enable(self, mock_healthcheck):
+        CONF.set_override('enabled', True, group='healthcheck')
+        self._make_app()
+        mock_healthcheck.assert_called_once_with(mock.ANY, CONF)
+
+    @mock.patch.object(healthcheck, 'Healthcheck')
+    def test_disable(self, mock_healthcheck):
+        CONF.set_override('enabled', False, group='healthcheck')
+        self._make_app()
+        self.assertFalse(mock_healthcheck.called)

releasenotes/notes/add-healthcheck-middleware-86120fa07a7c8151.yaml

@@ -0,0 +1,10 @@
+---
+features:
+  - |
+    Adds the healthcheck middleware from oslo, configurable via the
+    ``[healthcheck]/enabled`` option. This middleware adds a status check at
+    `/healthcheck`. This is useful for load balancers to determine if a service
+    is up (and add or remove it from rotation), or for monitoring tools to see
+    the health of the server. This endpoint is unauthenticated, as not all load
+    balancers or monitoring tools support authenticating with a health check
+    endpoint.

tools/config/ironic-config-generator.conf

@@ -10,6 +10,7 @@ namespace = ironic_lib.utils
 namespace = oslo.db
 namespace = oslo.messaging
 namespace = oslo.middleware.cors
+namespace = oslo.middleware.healthcheck
 namespace = oslo.concurrency
 namespace = oslo.policy
 namespace = oslo.log