master: annotate LogForwarder messages.

mitogen/master.py:
    Annotate forwarded log entries with their original source, logger
    name, and message.

ansible:
    mark stderr in red with -vvv

    Tempting to make this appaer 100% of the time, but some crappy
    bashrcs may cause lots of junk to be printed.

ansible_mitogen/logging.py

@@ -46,6 +46,9 @@ class Handler(logging.Handler):
         self.normal_method = normal_method
 
     def emit(self, record):
+        if getattr(record, 'mitogen_name', '') == 'stderr':
+            record.levelno = logging.ERROR
+
         s = '[pid %d] %s' % (os.getpid(), self.format(record))
         if record.levelno >= logging.ERROR:
             self.display.error(s, wrap_text=False)

docs/getting_started.rst

@@ -125,6 +125,19 @@ Logging Environment Variables
     logs of any IO interaction, which is useful when debugging deadlocks.
 
 
+
+Logging Records
+~~~~~~~~~~~~~~~
+
+Messages received from a child context via :class:`mitogen.master.LogForwarder`
+receive extra attributes:
+
+* `mitogen_context`: :class:`mitogen.master.Context` referring to the message
+  source.
+* `mitogen_name`: original logger name in the source context.
+* `mitogen_msg`: original message in the source context.
+
+
 Creating A Context
 ------------------
 

mitogen/master.py

@@ -309,7 +309,11 @@ class LogForwarder(object):
             self._cache[msg.src_id] = logger = logging.getLogger(name)
 
         name, level_s, s = msg.data.split('\x00', 2)
-        logger.log(int(level_s), '%s: %s', name, s)
+        logger.log(int(level_s), '%s: %s', name, s, extra={
+            'mitogen_message': s,
+            'mitogen_context': self._router.context_by_id(msg.src_id),
+            'mitogen_name': name,
+        })
 
     def __repr__(self):
         return 'LogForwarder(%r)' % (self._router,)