zuul/nodepool
Code Issues Proposed changes

Fix connection handling in recursive tree cache

Browse Source 
There were two errors related to connection handling in the new
treecache implementation:

1) Upon disconnection, the cache receives a "NONE" event with
the client state ("CONNECTING") and no path.  This is a signal to
the watcher that the connection state has changed.  Since we process
connection changes via the session listener, we should ignore this
event.  We were previously attempting to process it and assumed that
the path attribute would be present.  This change ignores NONE events
with no path.

2) The treecache is responsible for re-establishing watches if the
connection is LOST or SUSPENDED.  Previously, it would only
re-establish watches and refresh the cache if the connection was LOST.
This change updates it to re-establish/refresh in both cases.  The
"_started" variable is no longer necessary to distinguish between the
two.  However, it may be useful for future consumers to know whether
or not the cache is synced, so it is converted to "_ready" in case
we want to expose that in the future.

Change-Id: Id1f9c34628d1cc04881621a83d1d1f78e9e0f366
This commit is contained in:
James E. Blair 2023-05-02 14:42:31 -07:00
parent 3e8dce8873
commit c4c7052f10
2 changed files with 16 additions and 5 deletions
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8
nodepool/tests/unit/test_zk.py
View File

@ -1219,6 +1219,14 @@ class TestTreeCache(tests.DBTestCase):
'/test/foo': {},
})
# Simulate a change happening while the state was suspendede
cache._cached_paths.add('/test/bar')
cache._sessionListener(KazooState.SUSPENDED)
cache._sessionListener(KazooState.CONNECTED)
self.waitForCache(cache, {
'/test/foo': {},
})
def test_tree_cache_root(self):
client = self.zk.kazoo_client
data = b'{}'

13
nodepool/zk/zookeeper.py
View File

@ -741,7 +741,7 @@ class NodepoolTreeCache(abc.ABC):
self.root = root
self._cached_objects = {}
self._cached_paths = set()
self._started = False
self._ready = False
self._stopped = False
self._queue = queue.Queue()
self._background_thread = threading.Thread(
@ -763,9 +763,9 @@ class NodepoolTreeCache(abc.ABC):
def _sessionListener(self, state):
if state == KazooState.LOST:
self._started = False
elif (state == KazooState.CONNECTED and
not self._started and not self._stopped):
self._ready = False
elif state == KazooState.CONNECTED and not self._stopped:
self._ready = False
self.zk.kazoo_client.handler.short_spawn(self._start)
def _cacheListener(self, event):
@ -776,7 +776,7 @@ class NodepoolTreeCache(abc.ABC):
self.zk.kazoo_client.add_watch(self.root, self._cacheListener,
AddWatchMode.PERSISTENT_RECURSIVE)
self._walkTree()
self._started = True
self._ready = True
def stop(self):
self._stopped = True
@ -827,6 +827,9 @@ class NodepoolTreeCache(abc.ABC):
# as a delete which may be followed by a normal delete event.
# That case, and any other variations should be anticipated.
if event.type == EventType.NONE:
if event.path is None:
# We're probably being told of a connection change; ignore.
return
try:
data, stat = self.zk.kazoo_client.get(event.path)
exists = True