Add healthcheck middleware

Implements blueprint oslo-middleware-healthcheck
Change-Id: Id19a47c07ff4fbf954ab188b7186361ed9ef213a

3 files changed, 147 insertions, 0 deletions

diff --git a/oslo_middleware/healthcheck/__init__.py b/oslo_middleware/healthcheck/__init__.py
new file mode 100644
index 0000000..559770a
--- /dev/null
+++ b/oslo_middleware/healthcheck/__init__.py
@@ -0,0 +1,74 @@
+# Copyright 2011 OpenStack Foundation.
+# All Rights Reserved.
+#
+#    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.
+
+import stevedore
+import webob.dec
+import webob.exc
+import webob.response
+
+from oslo_middleware import base
+
+
+class Healthcheck(base.Middleware):
+    """Helper class that returns debug information.
+
+    Can be inserted into any WSGI application chain to get information about
+    the request and response.
+    """
+
+    NAMESPACE = "oslo.middleware.healthcheck"
+
+    @classmethod
+    def factory(cls, global_conf, **local_conf):
+        """Factory method for paste.deploy."""
+        conf = global_conf.copy()
+        conf.update(local_conf)
+
+        def healthcheck_filter(app):
+            return cls(app, conf)
+        return cls
+
+    def __init__(self, application, conf):
+        super(Healthcheck, self).__init__(application)
+        self._path = conf.get('path', '/healthcheck')
+        self._backend_names = []
+        backends = conf.get('backends')
+        if backends:
+            self._backend_names = backends.split(',')
+
+        self._backends = stevedore.NamedExtensionManager(
+            self.NAMESPACE, self._backend_names,
+            name_order=True, invoke_on_load=True,
+            invoke_args=(conf,))
+
+    @webob.dec.wsgify
+    def process_request(self, req):
+        if req.path != self._path:
+            return None
+
+        healthy = True
+        reasons = []
+        for ext in self._backends:
+            result = ext.obj.healthcheck()
+            healthy &= result.available
+            if result.reason:
+                reasons.append(result.reason)
+
+        return webob.response.Response(
+            status=(webob.exc.HTTPOk.code if healthy
+                    else webob.exc.HTTPServiceUnavailable.code),
+            body='\n'.join(reasons),
+            content_type="text/plain",
+        )
diff --git a/oslo_middleware/healthcheck/disable_by_file.py b/oslo_middleware/healthcheck/disable_by_file.py
new file mode 100644
index 0000000..7e964a4
--- /dev/null
+++ b/oslo_middleware/healthcheck/disable_by_file.py
@@ -0,0 +1,38 @@
+# Copyright 2011 OpenStack Foundation.
+# All Rights Reserved.
+#
+#    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.
+
+import logging
+import os
+
+from oslo_middleware.healthcheck import pluginbase
+from oslo_middleware.i18n import _LW
+
+LOG = logging.getLogger(__name__)
+
+
+class DisableByFileHealthcheck(pluginbase.HealthcheckBaseExtension):
+    def healthcheck(self):
+        path = self.conf.get('disable_by_file_path')
+        if path is None:
+            LOG.warning(_LW('DisableByFile healthcheck middleware enabled '
+                            'without disable_by_file_path set'))
+            return pluginbase.HealthcheckResult(available=True,
+                                                reason="")
+        elif not os.path.exists(path):
+            return pluginbase.HealthcheckResult(available=True,
+                                                reason="")
+        else:
+            return pluginbase.HealthcheckResult(available=False,
+                                                reason="DISABLED BY FILE")
diff --git a/oslo_middleware/healthcheck/pluginbase.py b/oslo_middleware/healthcheck/pluginbase.py
new file mode 100644
index 0000000..8c6e9d4
--- /dev/null
+++ b/oslo_middleware/healthcheck/pluginbase.py
@@ -0,0 +1,35 @@
+# Copyright 2011 OpenStack Foundation.
+# All Rights Reserved.
+#
+#    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.
+
+import abc
+import collections
+
+import six
+
+HealthcheckResult = collections.namedtuple(
+    'HealthcheckResult', ['available', 'reason'], verbose=True)
+
+
+@six.add_metaclass(abc.ABCMeta)
+class HealthcheckBaseExtension(object):
+    def __init__(self, conf):
+        self.conf = conf
+
+    @abc.abstractmethod
+    def healthcheck():
+        """method called by the healthcheck middleware
+
+        return: HealthcheckResult object
+        """