From 4e6a6deca6655d949daa69d5b5ef2e31b85532e6 Mon Sep 17 00:00:00 2001
From: Joshua Harlow <harlowja@yahoo-inc.com>
Date: Thu, 24 Apr 2014 16:29:11 -0700
Subject: [PATCH] Add a jobboard fetching context manager

Allow the jobboard backend to be fetched and automatically
connected and closed by providing a method that does the
fetching, connecting and closing as a context manager.

Change-Id: I3b2ea707009f8154f2c68652f101490c09f35c8c
---
 taskflow/jobs/backends/__init__.py | 12 ++++++++++++
 taskflow/jobs/jobboard.py          | 12 ++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/taskflow/jobs/backends/__init__.py b/taskflow/jobs/backends/__init__.py
index b720024b..0299636a 100644
--- a/taskflow/jobs/backends/__init__.py
+++ b/taskflow/jobs/backends/__init__.py
@@ -14,6 +14,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import contextlib
 import logging
 
 import six
@@ -53,3 +54,14 @@ def fetch(name, conf, namespace=BACKEND_NAMESPACE, **kwargs):
         return mgr.driver
     except RuntimeError as e:
         raise exc.NotFound("Could not find jobboard %s" % (board), e)
+
+
+@contextlib.contextmanager
+def backend(name, conf, namespace=BACKEND_NAMESPACE, **kwargs):
+    """Fetches a jobboard backend, connects to it and allows it to be used in
+    a context manager statement with the jobboard being closed upon completion.
+    """
+    jb = fetch(name, conf, namespace=namespace, **kwargs)
+    jb.connect()
+    with contextlib.closing(jb):
+        yield jb
diff --git a/taskflow/jobs/jobboard.py b/taskflow/jobs/jobboard.py
index 070b3ea3..0f3d4455 100644
--- a/taskflow/jobs/jobboard.py
+++ b/taskflow/jobs/jobboard.py
@@ -132,6 +132,18 @@ class JobBoard(object):
             this must be the same name that was used for claiming this job.
         """
 
+    @abc.abstractmethod
+    def connect(self):
+        """Opens the connection to any backend system."""
+
+    @abc.abstractmethod
+    def close(self):
+        """Close the connection to any backend system.
+
+        Once closed the jobboard can no longer be used (unless reconnection
+        occurs).
+        """
+
 
 # Jobboard events
 POSTED = 'POSTED'  # new job is/has been posted