kaisun2000 commented on a change in pull request #1119:
URL: https://github.com/apache/helix/pull/1119#discussion_r459111898
##########
File path:
zookeeper-api/src/main/java/org/apache/helix/zookeeper/zkclient/ZkClient.java
##########
@@ -1221,20 +1237,109 @@ private void reconnect() {
}
}
+ private class SyncCallbackHandler extends ZkAsyncCallbacks.DefaultCallback
implements AsyncCallback.VoidCallback {
+ private String _sessionId;
+
+ SyncCallbackHandler(String sessionId) {
+ _sessionId = sessionId;
+ }
+
+ @Override
+ public void processResult(int rc, String path, Object ctx) {
+ LOG.info("sycnOnNewSession with sessionID {} async return code: {}",
_sessionId, rc);
+ callback(rc, path, ctx);
+ }
+
+ @Override
+ public void handle() {
+ // Make compiler happy, not used.
+ }
+
+ @Override
+ protected boolean needRetry(int rc) {
+ try {
+ switch (KeeperException.Code.get(rc)) {
+ /** Connection to the server has been lost */
+ case CONNECTIONLOSS:
+ return true;
+ default:
+ return false;
+ }
+ } catch (ClassCastException | NullPointerException ex) {
+ LOG.error("Session {} failed to handle unknown return code {}. Skip
retrying. ex {}",
+ _sessionId, rc, ex);
+ return false;
+ }
+ }
+ }
+
+ private void doAsyncSync(final ZooKeeper zk, final String path, final long
startT,
+ final SyncCallbackHandler cb) {
+ zk.sync(path, cb,
+ new ZkAsyncRetryCallContext(_asyncCallRetryThread, cb, _monitor,
startT, 0, false) {
+ @Override
+ protected void doRetry() throws Exception {
+ doAsyncSync(zk, path, startT, cb);
+ }
+ });
+ }
+
+ private boolean retrySync(String sessionId) throws ZkInterruptedException {
+ if (!_syncOnNewSession) {
+ return true;
+ }
+
+ SyncCallbackHandler callbackHandler = new SyncCallbackHandler(sessionId);
+
+ final ZkConnection zkConnection = (ZkConnection) getConnection();
Review comment:
Just saw this comment.
The gist is that the checking of sessionId and doAsyncSync() is not atomic.
After `if (zk.getSessionId().equals(sessionId))` succeed, the Zookeeper object
may be changed due to a new session established. This would make the current
doAsyncSync() work for the new session. Since the new session would trigger
another fireNewSession(), which would put another retrySync(). Then we will
have another sync() to the Zookeeper for the new session. So in sum, the new
session can be two sync() in a row.
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