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Fix race condition on configuration writeback

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If the sync thread had moved beyond the point of checking _writepending, but had not quite managed to trigger
isAlive() to be false, the sync cfg to file would transition to never work.  Address this by adding one lock and one boolean.
Inside the lock, the two booleans are manipulated to atomically mark the end of thread sync activity linked with
check for pending data to write.
This commit is contained in:
Jarrod Johnon 2014-09-19 08:57:17 -04:00
parent e9ac1617a8
commit 89ca5b412b
1 changed files with 17 additions and 11 deletions
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28
confluent_server/confluent/config/configmanager.py
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@ -405,6 +405,8 @@ class ConfigManager(object):
_cfgdir = "/etc/confluent/cfg/"
_cfgwriter = None
_writepending = False
_syncrunning = False
_syncstate = threading.RLock()
_attribwatchers = {}
_nodecollwatchers = {}
_notifierids = {}
@ -1123,15 +1125,13 @@ class ConfigManager(object):
@classmethod
def _bg_sync_to_file(cls):
if cls._writepending:
# already have a write scheduled
return
elif cls._cfgwriter is not None and cls._cfgwriter.isAlive():
#write in progress, request write when done
cls._writepending = True
else:
cls._cfgwriter = threading.Thread(target=cls._sync_to_file)
cls._cfgwriter.start()
with cls._syncstate:
if cls._syncrunning:
cls._writepending = True
return
cls._syncrunning = True
cls._cfgwriter = threading.Thread(target=cls._sync_to_file)
cls._cfgwriter.start()
@classmethod
def _sync_to_file(cls):
@ -1170,8 +1170,14 @@ class ConfigManager(object):
del dbf[ck]
else:
dbf[ck] = cPickle.dumps(currdict[category][ck])
if cls._writepending:
cls._writepending = False
willrun = False
with cls._syncstate:
if cls._writepending:
cls._writepending = False
willrun = True
else:
cls._syncrunning = False
if willrun:
return cls._sync_to_file()
def _recalculate_expressions(self, cfgobj, formatter, node, changeset):