bitbake: server/process: Improve exception and idle function logging

Currently if the idle functions loop suffers a traceback, it is
silently dropped and there is no log message to say what happened.
This change at least means the traceback is in the cooker log, making
some debugging possible.

Add some logging to show when handlers are added/removed to allow
a better idea of what the server code is doing from the server log
file.

(Bitbake rev: 9cf3102dc36513124fe5ead2f1e448b51833b6ac)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/server/process.py

@@ -106,6 +106,7 @@ class ProcessServer():
         """Register a function to be called while the server is idle"""
         assert hasattr(function, '__call__')
         self._idlefuns[function] = data
+        serverlog("Registering idle function %s" % str(function))
 
     def run(self):
 
@@ -361,6 +362,7 @@ class ProcessServer():
             try:
                 retval = function(self, data, False)
                 if retval is False:
+                    serverlog("Removing idle function %s" % str(function))
                     del self._idlefuns[function]
                     nextsleep = None
                 elif retval is True:
@@ -378,6 +380,7 @@ class ProcessServer():
                 if not isinstance(exc, bb.BBHandledException):
                     logger.exception('Running idle function')
                 del self._idlefuns[function]
+                serverlog("Exception %s broke the idle_thread, exiting" % traceback.format_exc())
                 self.quit = True
 
         # Create new heartbeat event?
@@ -395,6 +398,7 @@ class ProcessServer():
                 except Exception as exc:
                     if not isinstance(exc, bb.BBHandledException):
                         logger.exception('Running heartbeat function')
+                    serverlog("Exception %s broke in idle_commands, exiting" % traceback.format_exc())
                     self.quit = True
         if nextsleep and bb.event._heartbeat_enabled and now + nextsleep > self.next_heartbeat:
             # Shorten timeout so that we we wake up in time for