Why Watch keyword is used in zookeeper?

0 votes

Hi,

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

May 27 in Big Data Hadoop by Naina

edited May 27 by Gitika 23 views

1 answer to this question.

0 votes

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.

answered May 27 by Gitika
• 25,340 points

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