Allow docker plugin to run w/o deps

The docker plugin tests would not run without the docker lib being
installed even though the client was mocked in the tests. This
patch adds conditional import of the client and registration of
the plugin so that the contrib tests can be run in the gates
without having to hack requirements or add more third party
libs.

Change-Id: Ia114f8ebc0cf0b72af8e6e5d2c3264fb7952d7f9
Partial-Bug: #1251380

contrib/docker-plugin/plugin/docker_container.py

@@ -17,9 +17,19 @@
 
 from heat.engine import properties
 from heat.engine import resource
+from heat.openstack.common import log as logging
 from heat.openstack.common.gettextutils import _
 
-import docker
+logger = logging.getLogger(__name__)
+
+DOCKER_INSTALLED = False
+# conditionally import so tests can work without having the dependency
+# satisfied
+try:
+    import docker
+    DOCKER_INSTALLED = True
+except ImportError:
+    docker = None
 
 
 class DockerContainer(resource.Resource):
@@ -128,13 +138,14 @@ class DockerContainer(resource.Resource):
         'logs_tail': _('Container last logs line')
     }
 
-    docker_client = docker.Client()
-
     def get_client(self):
-        client = self.docker_client
-        endpoint = self.properties.get('docker_endpoint')
-        if endpoint:
-            client = docker.Client(endpoint)
+        client = None
+        if DOCKER_INSTALLED:
+            endpoint = self.properties.get('docker_endpoint')
+            if endpoint:
+                client = docker.Client(endpoint)
+            else:
+                client = docker.Client()
         return client
 
     def _parse_networkinfo_ports(self, networkinfo):
@@ -261,6 +272,11 @@ class DockerContainer(resource.Resource):
 
 
 def resource_mapping():
-    return {
-        'OS::Docker::Container': DockerContainer
-    }
+    # only register if docker client installed
+    if DOCKER_INSTALLED:
+        return {
+            'OS::Docker::Container': DockerContainer
+        }
+    else:
+        logger.warn("Docker plug-in loaded, but docker lib not installed.")
+    return {}

contrib/docker-plugin/tests/test_docker_container.py

@@ -51,8 +51,8 @@ class DockerContainerTest(HeatTestCase):
     def setUp(self):
         super(DockerContainerTest, self).setUp()
         utils.setup_dummy_db()
-        for res_name, res_class in docker_container.resource_mapping().items():
-            resource._register_class(res_name, res_class)
+        resource._register_class('OS::Docker::Container',
+                                 docker_container.DockerContainer)
 
     def create_container(self, resource_name):
         t = template_format.parse(template)