jiajunwang commented on a change in pull request #1119:
URL: https://github.com/apache/helix/pull/1119#discussion_r459124001
##########
File path:
zookeeper-api/src/main/java/org/apache/helix/zookeeper/zkclient/ZkClient.java
##########
@@ -1221,21 +1234,84 @@ private void reconnect() {
}
}
+
+
+ private void doAsyncSync(final ZooKeeper zk, final String path, final long
startT,
+ final ZkAsyncCallbacks.SyncCallbackHandler cb) {
+ zk.sync(path, cb,
+ new ZkAsyncRetryCallContext(_asyncCallRetryThread, cb, _monitor,
startT, 0, true) {
+ @Override
+ protected void doRetry() throws Exception {
+ doAsyncSync(zk, path, System.currentTimeMillis(), cb);
+ }
+ });
+ }
+
+ /*
+ * Note, issueSync takes a ZooKeeper (client) object and pass it to
doAsyncSync().
+ * The reason we do this is that we want to ensure each new session event
is preceded with exactly
+ * one sync() to server. The sync() is to make sure the server would not
see stale data.
+ *
+ * ZooKeeper client object has an invariant of each object has one session.
With this invariant
+ * we can achieve each one sync() to server upon new session establishment.
The reasoning is:
+ * issueSync() is called when fireNewSessionEvents() which in under
eventLock of ZkClient. Thus
+ * we are guaranteed the ZooKeeper object passed in would have the new
incoming sessionId. If by
+ * the time sync() is invoked, the session expires. The sync() would fail
with a stale session.
+ * This is exactly what we want. The newer session would ensure another
fireNewSessionEvents.
+ */
+ private boolean issueSync(String sessionId, ZooKeeper zk) throws
ZkInterruptedException {
Review comment:
“Please see my reply to the original thread.”, where I mentioned that
this con is not real : )
When you get the zk first then compared it with the session Id, you will
have the right zk to use for sure. Or the check will fail and we will not
really send sync request.
----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
For queries about this service, please contact Infrastructure at:
[email protected]
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
