Add ComputeNode Tracker

A ComputeNodeTracker class, very similar to the resource_tracker.py
of nova[1] at nova/compute/resource_tracker.py with a few changes.

This does not implement any in memory cache for the compute_nodes
but reads the data everytime from the db. This can be improved or
kept as is. This also imposes the compute_node object contract on
the driver API for available resources so that random keys are not
used instead the object fields are honored.

[1]: https://github.com/openstack/nova/

Change-Id: I1e3aa35ad9927b0d29c8970a5fa3cb6530df281f

zun/compute/compute_node_tracker.py

@@ -0,0 +1,49 @@
+# 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.
+
+from oslo_log import log as logging
+
+from zun.common import exception
+from zun.common.i18n import _LI
+from zun.common.i18n import _LW
+from zun import objects
+
+LOG = logging.getLogger(__name__)
+
+
+class ComputeNodeTracker(object):
+    def __init__(self, host, container_driver):
+        self.host = host
+        self.container_driver = container_driver
+
+    def update_available_resources(self, context):
+        # Check if the compute_node is already registered
+        node = self._get_compute_node(context, self.host)
+        if not node:
+            # If not, register it and pass the object to the driver
+            node = objects.NodeInfo(context)
+            node.hostname = self.host
+            node.create()
+            LOG.info(_LI('Node created for :%(host)s'), {'host': self.host})
+        self.container_driver.get_available_resources(node)
+        # NOTE(sbiswas7): Consider removing the return statement if not needed
+        return node
+
+    def _get_compute_node(self, context):
+        """Returns compute node for the host"""
+        try:
+            return objects.NodeInfo.get_by_hostname(context, self.host)
+        except exception.NotFound:
+            LOG.warning(_LW("No compute node record for: %(host)s"),
+                        {'host': self.host})

zun/container/driver.py

@@ -158,9 +158,7 @@ class ContainerDriver(object):
         """Update a container."""
         raise NotImplementedError()
 
-    def get_available_resources(self):
-        data = {}
+    def get_available_resources(self, compute_node_obj):
         numa_topo_obj = objects.NUMATopology()
         os_capability_linux.LinuxHost().get_host_numa_topology(numa_topo_obj)
-        data['numa_topology'] = numa_topo_obj
-        return data
+        compute_node_obj.numa_topology = numa_topo_obj

zun/tests/unit/container/docker/test_docker_driver.py

@@ -17,6 +17,7 @@ from zun import conf
 from zun.container.docker.driver import DockerDriver
 from zun.container.docker.driver import NovaDockerDriver
 from zun.container.docker import utils as docker_utils
+from zun import objects
 from zun.objects import fields
 from zun.tests.unit.container import base
 from zun.tests.unit.db import utils as db_utils
@@ -540,5 +541,6 @@ class TestNovaDockerDriver(base.DriverTestCase):
     def test_get_available_resources(self, mock_output):
         mock_output.return_value = LSCPU_ON
         conf.CONF.set_override('floating_cpu_set', "0")
-        output = self.driver.get_available_resources()
-        self.assertEqual(_numa_topo_spec, output['numa_topology'].to_list())
+        node_obj = objects.ComputeNode()
+        self.driver.get_available_resources(node_obj)
+        self.assertEqual(_numa_topo_spec, node_obj.numa_topology.to_list())