xyuanlu commented on code in PR #2409:
URL: https://github.com/apache/helix/pull/2409#discussion_r1144092886
##########
meta-client/src/main/java/org/apache/helix/metaclient/impl/zk/ZkMetaClient.java:
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@@ -266,18 +279,25 @@ public void asyncSet(String key, T data, int version,
AsyncCallback.StatCallback
@Override
public void connect() {
- // TODO: throws IllegalStateException when already connected
try {
+ _zkClientConnectionMutex.lock();
_zkClient.connect(_initConnectionTimeout, _zkClient);
+ // register this client as state change listener to react to ZkClient
EXPIRED event.
+ // When ZkClient has expired connection to ZK, it sill auto reconnect
until ZkClient
+ // is closed or connection re-established.
+ // We will need to close ZkClient when user set retry connection timeout.
+ _zkClient.subscribeStateChanges(this);
Review Comment:
TFTR. This is a good point.
As our offline discussed, since ZkClient has a single thread (_eventThread)
handling all events, it is possible that one previous event handling callback
blocking all following event being send out. This is a generic problem with
single event thread. To coup with this, we
1. Mentioned explicitly in document that user should not register blocking
callbacks to client. (ZooKeeper document also suggested this)
2. In Helix use case, all callbacks are just simply forward.
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