lvmdbusd: Exit daemon when unable to retrieve state

In some cases we get stuck where we are unable to retrieve the current
state of lvm as we are encountering an error.  When the error is
persistent we will log and exit the daemon instead of consuming vast
amounts of resources.

Signed-off-by: Tony Asleson <tasleson@redhat.com>

daemons/lvmdbusd/cfg.py

@@ -87,3 +87,13 @@ blackbox = None
 
 # RequestEntry ctor
 create_request_entry = None
+
+
+def exit_daemon():
+    """
+    Exit the daemon cleanly
+    :return:
+    """
+    if run and loop:
+        run.value = 0
+        loop.quit()

daemons/lvmdbusd/fetch.py

@@ -14,6 +14,7 @@ from . import cfg
 from .utils import MThreadRunner, log_debug, log_error
 import threading
 import queue
+import time
 import traceback
 
 
@@ -82,6 +83,8 @@ class StateUpdate(object):
 
 	@staticmethod
 	def update_thread(obj):
+		exception_count = 0
+
 		queued_requests = []
 		while cfg.run.value != 0:
 			# noinspection PyBroadException
@@ -136,12 +139,26 @@ class StateUpdate(object):
 				# wake up if we get an exception
 				queued_requests = []
 
+				# We retrieved OK, clear exception count
+				exception_count = 0
+
 			except queue.Empty:
 				pass
-			except Exception:
+			except Exception as e:
 				st = traceback.format_exc()
 				log_error("update_thread exception: \n%s" % st)
 				cfg.blackbox.dump()
+				exception_count += 1
+				if exception_count >= 5:
+					for i in queued_requests:
+						i.set_result(e)
+
+					log_error("Too many errors in update_thread, exiting daemon")
+					cfg.exit_daemon()
+
+				else:
+					# Slow things down when encountering errors
+					time.sleep(1)
 
 	def __init__(self):
 		self.lock = threading.RLock()