introduce argument allowing the formatter to ignore key errors

Author: sleongkoan

fluent/handler.py

@@ -23,8 +23,12 @@ class FluentRecordFormatter(logging.Formatter, object):
     Best used with server storing data in an ElasticSearch cluster for example.
 
     :param fmt: a dict with format string as values to map to provided keys.
+    :param datefmt: strftime()-compatible date/time format string.
+    :param style: (NOT USED)
+    :param fill_missing_fmt_key: if True, do not raise a KeyError if the format
+        key is not found. Put None if not found.s
     """
-    def __init__(self, fmt=None, datefmt=None, style='%'):
+    def __init__(self, fmt=None, datefmt=None, style='%', fill_missing_fmt_key=False):
         super(FluentRecordFormatter, self).__init__(None, datefmt)
 
         if not fmt:
@@ -38,6 +42,8 @@ def __init__(self, fmt=None, datefmt=None, style='%'):
 
         self.hostname = socket.gethostname()
 
+        self.fill_missing_fmt_key = fill_missing_fmt_key
+
     def format(self, record):
         # Only needed for python2.6
         if sys.version_info[0:2] <= (2, 6) and self.usesTime():
@@ -47,9 +53,18 @@ def format(self, record):
         super(FluentRecordFormatter, self).format(record)
         # Add ours
         record.hostname = self.hostname
+
         # Apply format
-        data = dict([(key, value % record.__dict__)
-                     for key, value in self._fmt_dict.items()])
+        data = {}
+        for key, value in self._fmt_dict.items():
+            try:
+                value = value % record.__dict__
+            except KeyError as exc:
+                value = None
+                if not self.fill_missing_fmt_key:
+                    raise exc
+
+            data[key] = value
 
         self._structuring(data, record)
         return data