Why Watch keyword is used in zookeeper

Question

Hi,

I am not able to understand the concept of Watch keyword in zookeeeper, how it is going to make any change?

Answer 1

Hey,

Watches show a notification when the specified znode or znode’s children data changes. You can set a watch only to get command:-

Syntax:-

get /path [watch] 1

Sample:-

get /FirstZnode 1

Output:-

[zk: localhost:2181(CONNECTED) 1] get /FirstZnode 1
“Myfirstzookeeper-app”
cZxid = 0x7f
ctime = Tue Sep 29 16:15:47 IST 2015
mZxid = 0x7f
mtime = Tue Sep 29 16:15:47 IST 2015
pZxid = 0x7f
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 22
numChildren = 0

The output is similar to normal get command, but it will wait for znode changes in the background.