From 9f7922a7ca2eb3e9ee1c15fcb78fc2706fffb280 Mon Sep 17 00:00:00 2001
From: Hongbin Lu <hongbin034@gmail.com>
Date: Sat, 18 Jan 2020 22:16:59 +0000
Subject: [PATCH] Load container driver from entry point

Change-Id: I66fed92c4f67b4552aca3bd8d81b6dda32d70442
---
 devstack/lib/zun                              |  2 +-
 .../container_driver-e82fe9c64c9b994b.yaml    | 11 +++++++++++
 setup.cfg                                     |  4 ++++
 zun/conf/container_driver.py                  |  4 ++--
 zun/container/driver.py                       | 19 +++++++++++++++++--
 .../unit/compute/test_compute_manager.py      |  4 +---
 6 files changed, 36 insertions(+), 8 deletions(-)
 create mode 100644 releasenotes/notes/container_driver-e82fe9c64c9b994b.yaml

diff --git a/devstack/lib/zun b/devstack/lib/zun
index b5cd46bad..d014b9eb7 100644
--- a/devstack/lib/zun
+++ b/devstack/lib/zun
@@ -174,7 +174,7 @@ function create_zun_conf {
     # (Re)create ``zun.conf``
     rm -f $ZUN_CONF
     if [[ ${ZUN_DRIVER} == "docker" ]]; then
-        iniset $ZUN_CONF DEFAULT container_driver docker.driver.DockerDriver
+        iniset $ZUN_CONF DEFAULT container_driver docker
     fi
     iniset $ZUN_CONF DEFAULT debug "$ENABLE_DEBUG_LOG_LEVEL"
     if [[ $SERVICE_IP_VERSION == 6 ]]; then
diff --git a/releasenotes/notes/container_driver-e82fe9c64c9b994b.yaml b/releasenotes/notes/container_driver-e82fe9c64c9b994b.yaml
new file mode 100644
index 000000000..bd5dbf3a3
--- /dev/null
+++ b/releasenotes/notes/container_driver-e82fe9c64c9b994b.yaml
@@ -0,0 +1,11 @@
+---
+upgrade:
+  - |
+    Starting from this release, container driver is loaded from entry point.
+    Deployers should specify the entry point (i.e. ``docker``) in config option
+    ``container_driver`` under ``[DEFAULT]`` session.
+deprecations:
+  - |
+    Specifying container driver class via config option ``container_driver``
+    is deprecated. Use driver name in entry point ``zun.container.driver``
+    instead.
diff --git a/setup.cfg b/setup.cfg
index 60d0a5880..0141229ec 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -68,6 +68,10 @@ zun.scheduler.driver =
     fake_scheduler = zun.tests.unit.scheduler.fakes:FakeScheduler
     filter_scheduler = zun.scheduler.filter_scheduler:FilterScheduler
 
+zun.container.driver =
+    docker = zun.container.docker.driver:DockerDriver
+    fake = zun.tests.unit.container.fake_driver:FakeDriver
+
 zun.image.driver =
     glance = zun.image.glance.driver:GlanceDriver
     docker = zun.image.docker.driver:DockerDriver
diff --git a/zun/conf/container_driver.py b/zun/conf/container_driver.py
index 92813f19d..fa27d75f9 100644
--- a/zun/conf/container_driver.py
+++ b/zun/conf/container_driver.py
@@ -15,11 +15,11 @@ from oslo_config import cfg
 
 driver_opts = [
     cfg.StrOpt('container_driver',
-               default='docker.driver.DockerDriver',
+               default='docker',
                help="""Defines which driver to use for controlling container.
 Possible values:
 
-* ``docker.driver.DockerDriver``
+* ``docker``
 
 Services which consume this:
 
diff --git a/zun/container/driver.py b/zun/container/driver.py
index e309d75db..0fad80a66 100644
--- a/zun/container/driver.py
+++ b/zun/container/driver.py
@@ -18,6 +18,7 @@ import os_resource_classes as orc
 from oslo_log import log as logging
 from oslo_utils import importutils
 from oslo_utils import units
+from stevedore import driver as stevedore_driver
 
 from zun.common.i18n import _
 from zun.common import utils
@@ -51,9 +52,23 @@ def load_container_driver(container_driver=None):
 
     LOG.info("Loading container driver '%s'", container_driver)
     try:
-        if not container_driver.startswith('zun.'):
+        if container_driver.startswith('docker.driver.'):
+            # case 1: (deprecated) CONF.container_driver is
+            # 'docker.driver.DockerDriver'
             container_driver = 'zun.container.%s' % container_driver
-        driver = importutils.import_object(container_driver)
+            driver = importutils.import_object(container_driver)
+        elif container_driver.startswith('zun.'):
+            # case 2: (deprecated) CONF.container_driver is
+            # 'zun.container.docker.driver.DockerDriver'
+            driver = importutils.import_object(container_driver)
+        else:
+            # case 3: CONF.container_driver is (for example) 'docker'
+            # load from entry point in this case.
+            driver = stevedore_driver.DriverManager(
+                "zun.container.driver",
+                container_driver,
+                invoke_on_load=True).driver
+
         if not isinstance(driver, ContainerDriver):
             raise Exception(_('Expected driver of type: %s') %
                             str(ContainerDriver))
diff --git a/zun/tests/unit/compute/test_compute_manager.py b/zun/tests/unit/compute/test_compute_manager.py
index 3cae80df9..a20b4fbfe 100644
--- a/zun/tests/unit/compute/test_compute_manager.py
+++ b/zun/tests/unit/compute/test_compute_manager.py
@@ -99,9 +99,7 @@ class TestManager(base.TestCase):
         p.start()
         self.addCleanup(p.stop)
 
-        zun.conf.CONF.set_override(
-            'container_driver',
-            'zun.tests.unit.container.fake_driver.FakeDriver')
+        zun.conf.CONF.set_override('container_driver', 'fake')
         self.compute_manager = manager.Manager()
         self.compute_manager._resource_tracker = FakeResourceTracker()