Zookeeper watches :: No notification in case of child node modification - apache-zookeeper

Question

We are seeing an issue with zookeeper watches. We creating a node “/newtest” and intent is to add/modify nodes inside it. We are putting a watch on "/newtest”. Our observation is that if a child is added or deleted we get the notification but if a child is modified we do not get the notification.
Below is the output from zkCli.sh commands
========
[zk: localhost:2181(CONNECTED) 21] ls /newtest watch <=== to get the child nodes plus the watch
[1, 5, 4] <=== 1,5, 4 are the child nodes
[zk: localhost:2181(CONNECTED) 24] set /newtest/5 hello6 <=== updating the data for node “5”, no watch notification
cZxid = 0xc16
ctime = Fri Mar 11 01:03:29 UTC 2016
mZxid = 0xc78
mtime = Fri Mar 11 01:19:48 UTC 2016
pZxid = 0xc16
cversion = 0
dataVersion = 2
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 6
numChildren = 0
[zk: localhost:2181(CONNECTED) 25] create /newtest/6 hello6 <=== creating a new node
WATCHER::
Created /newtest/6
WatchedEvent state:SyncConnected type:NodeChildrenChanged path:/newtest <== watcher notification
[zk: localhost:2181(CONNECTED) 26] ls /newtest watch <=== Again watch
[1, 6, 5, 4]
[zk: localhost:2181(CONNECTED) 27] set /newtest/6 hello6 <== updating node “6”, no notification
cZxid = 0xc79
ctime = Fri Mar 11 01:19:59 UTC 2016
mZxid = 0xc86
mtime = Fri Mar 11 01:23:18 UTC 2016
pZxid = 0xc79
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 6
numChildren = 0
========
Please suggest a solution. Zookeeper version is zookeeper.version=3.4.6--1

Answer 1

I would suggest not using zkCli.sh for anything other than testing and small/quick operations. If you want to get notifications when a child node is modified I would suggest writing your own watchers in Java using Apache Curator, and more specifically using a Tree Cache.