Hi Scott, The R client could receive either version 1 or version 2. In the case it receives version 1, it will receive the notification for the version 2 change once the server the client is connected to receives the update. If the getData returns version 2 instead, it won't get the watch triggered by the setData of steps 2 and 3 below. It should get it triggered by a future update, though, assuming there is one.
-Flavio -----Original Message----- From: Scott Fines [mailto:[email protected]] Sent: 23 May 2013 14:48 To: [email protected] Subject: Understanding event interleaving Hello all, This is perhaps a silly question, but one I'm not clear on. Suppose you have two clients (R and W), and they are interacting through znode Z. Now consider the following situation: 0. Z at version 1 1. R begins getData(Z) (attach Watcher) 2. W begins setData(Z) 3. W completed setData(Z) successfully --e.g. the client call returns with no errors 4. R completes getData(Z) successfully -- e.g. the client call returns with no errors My questions are then: 1. What version of data will R receive? Version 1, or Version 2? My assumption here is that R would receive version 1 of the data--is that correct? 2. Does R's watch fire with the changes made by W? If so, is a WatchEvent delivered all the way to the caller? A comment made on ZOOKEEPER-1505 (https://issues.apache.org/jira/browse/ZOOKEEPER-1505) implies that it would not, but I'm unclear if that is in reference to the proposed changes or not. Thanks for your help! Scott Fines
