Do not log stack traces when out of disk

This commit silences monasca-notifications in situations where
it cannot write to its log file due to ENOSPC by preventing
the logging module from raising exceptions (recommended best
practice for production use).

The old behaviour can be restored by setting the
logging/raise_exceptions setting in the configuration file to
True (defaults to False).

Change-Id: Idbe5bdf56fb280412c34f04de8f2e2f301a7a432
Story: 2001089
Task: 4749

monasca_notification/main.py

@@ -102,6 +102,14 @@ def main(argv=None):
     config = yaml.safe_load(open(config_file, 'r'))
 
     # Setup logging
+    try:
+        if config['logging']['raise_exceptions'] is True:
+            logging.raiseExceptions = True
+        else:
+            logging.raiseExceptions = False
+    except KeyError:
+        logging.raiseExceptions = False
+        pass
     logging.config.dictConfig(config['logging'])
 
     for proc in range(0, config['processors']['notification']['number']):

notification.yaml

@@ -89,6 +89,9 @@ zookeeper:
         60: /notification/60_seconds
 
 logging: # Used in logging.dictConfig
+    # This sets logging.raiseExcetpions. It is recommended to leave this set to False.
+    # See https://docs.python.org/2/howto/logging.html#exceptions-raised-during-logging
+    raise_exceptions: False
     version: 1
     disable_existing_loggers: False
     formatters: