How to check the list of watches

How to check the list of watches

Zookeeper use watches to notify a client on znode changes. This article explains how to check watches set by ZooKeeper servers and how it is used.

Solution:

Zookeeper uses the 'wchc' command to list all watches set on the Zookeeper server.

# echo wchc | nc zookeeper 2181

Reference

https://zookeeper.apache.org/doc/r3.4.12/zookeeperAdmin.html

The wchp and wchc commands are not enabled by default because of their known DOS vulnerability. For more information, see ZOOKEEPER-2693and Zookeeper 3.5.2 - Denial of Service.

By default those commands are disabled, they can be enabled via Java system property:

-Dzookeeper.4lw.commands.whitelist=*

on in zookeeper config: 4lw.commands.whitelist=*\

Last modified 2021.08.12 : General corrections and updates. (5969b688)