add LoggingConfigurable base class

IPython/config/configurable.py

@@ -261,3 +261,18 b' class SingletonConfigurable(Configurable):'
         """Has an instance been created?"""
         return hasattr(cls, "_instance") and cls._instance is not None
 
+
+class LoggingConfigurable(Configurable):
+    """A parent class for Configurables that log.
+    
+    Subclasses have a log trait, and the default behavior
+    is to get the logger from the currently running Application
+    via Application.instance().log.
+    """
+    
+    log = Instance('logging.Logger')
+    def _log_default(self):
+        from IPython.config.application import Application
+        return Application.instance().log
+        
+        
  No newline at end of file

IPython/parallel/apps/launcher.py

@@ -50,7 +50,7 b' except ImportError:'
 from zmq.eventloop import ioloop
 
 from IPython.config.application import Application
-from IPython.config.configurable import Configurable
+from IPython.config.configurable import LoggingConfigurable
 from IPython.utils.text import EvalFormatter
 from IPython.utils.traitlets import Any, Int, List, Unicode, Dict, Instance
 from IPython.utils.path import get_ipython_module_path
@@ -96,7 +96,7 b' class UnknownStatus(LauncherError):'
     pass
 
 
-class BaseLauncher(Configurable):
+class BaseLauncher(LoggingConfigurable):
     """An asbtraction for starting, stopping and signaling a process."""
 
     # In all of the launchers, the work_dir is where child processes will be
@@ -108,9 +108,6 b' class BaseLauncher(Configurable):'
     # the work_dir option.
     work_dir = Unicode(u'.')
     loop = Instance('zmq.eventloop.ioloop.IOLoop')
-    log = Instance('logging.Logger')
-    def _log_default(self):
-        return Application.instance().log
     
     start_data = Any()
     stop_data = Any()

IPython/parallel/apps/logwatcher.py

@@ -19,8 +19,7 b' import sys'
 import zmq
 from zmq.eventloop import ioloop, zmqstream
 
-from IPython.config.application import Application
-from IPython.config.configurable import Configurable
+from IPython.config.configurable import LoggingConfigurable
 from IPython.utils.traitlets import Int, Unicode, Instance, List
 
 #-----------------------------------------------------------------------------
@@ -28,17 +27,13 b' from IPython.utils.traitlets import Int, Unicode, Instance, List'
 #-----------------------------------------------------------------------------
 
 
-class LogWatcher(Configurable):
+class LogWatcher(LoggingConfigurable):
     """A simple class that receives messages on a SUB socket, as published
     by subclasses of `zmq.log.handlers.PUBHandler`, and logs them itself.
     
     This can subscribe to multiple topics, but defaults to all topics.
     """
     
-    log = Instance('logging.Logger')
-    def _log_default(self):
-        return Application.instance().log
-    
     # configurables
     topics = List([''], config=True,
         help="The ZMQ topics to subscribe to. Default is to subscribe to all messages")

IPython/parallel/controller/dictdb.py

@@ -44,8 +44,7 b' We support a subset of mongodb operators:'
 
 from datetime import datetime
 
-from IPython.config.application import Application
-from IPython.config.configurable import Configurable
+from IPython.config.configurable import LoggingConfigurable
 
 from IPython.utils.traitlets import Dict, Unicode, Instance
 
@@ -80,13 +79,10 b' class CompositeFilter(object):'
                 return False
         return True
 
-class BaseDB(Configurable):
+class BaseDB(LoggingConfigurable):
     """Empty Parent class so traitlets work on DB."""
     # base configurable traits:
     session = Unicode("")
-    log = Instance('logging.Logger')
-    def _log_default(self):
-        return Application.instance().log
 
 class DictDB(BaseDB):
     """Basic in-memory dict-based object for saving Task Records.

IPython/parallel/controller/heartmonitor.py

@@ -18,8 +18,7 b' import zmq'
 from zmq.devices import ThreadDevice
 from zmq.eventloop import ioloop, zmqstream
 
-from IPython.config.application import Application
-from IPython.config.configurable import Configurable
+from IPython.config.configurable import LoggingConfigurable
 from IPython.utils.traitlets import Set, Instance, CFloat
 
 class Heart(object):
@@ -48,7 +47,7 b' class Heart(object):'
     def start(self):
         return self.device.start()
         
-class HeartMonitor(Configurable):
+class HeartMonitor(LoggingConfigurable):
     """A basic HeartMonitor class
     pingstream: a PUB stream
     pongstream: an XREP stream
@@ -59,10 +58,6 b' class HeartMonitor(Configurable):'
         ' (in ms) [default: 100]',
     )
     
-    log = Instance('logging.Logger')
-    def _log_default(self):
-        return Application.instance().log
-    
     pingstream=Instance('zmq.eventloop.zmqstream.ZMQStream')
     pongstream=Instance('zmq.eventloop.zmqstream.ZMQStream')
     loop = Instance('zmq.eventloop.ioloop.IOLoop')