How to watch child child nodes in Python using kazoo?

Question

I recently started working with Python for Zookeeper. I use the library kazoofor Zookeeper.

I have a very simple example of using kazoo for Zookeeper. I have a root node, which is - /root. Now I need to monitor the root of the node /root, and if the new node that is being added to the root node /rootis this /root/testing, then I will only store the clock on the /root/testingnode. I do not want to keep track of any nodes other than testingnode. And then if any new children are added to the /root/testingnode, I will also look at them.

Say a child below this is added -

`/root/testing/test1`

Then I will look at test1node.

Can this be done with Kazoo in Zookeeper? I can only keep track of one Zookeeper node ( /root) using the code below:

#!/usr/bin/python
import time

from kazoo.client import KazooClient

zk = KazooClient(hosts='127.0.0.1:2181')
zk.start()

########################################
@zk.ChildrenWatch("/root/testing")
def watch_children(children):
   print(children)

########################################

while True:
    time.sleep(5)

Can someone help me with this in creating a few hours for a child node?

Answer 1

Try something like this.

import time
from kazoo.client import KazooClient

zk = KazooClient(hosts='127.0.0.1:2181')
zk.start()

children = zk.get_children("/root/",)
if "/testing" in children:
    children_testing = zk.get_children("/root/testing/")
        if children_testing != []: 
            @zk.ChildrenWatch("/root/testing")
            def watch_children(children):
                print(children)
        else:
            @zk.ChildrenWatch("/root/")
            def watch_children(children):
                print(children)
while True:
    time.sleep(5)

Answer 2

If you are trying to monitor multiple nodes, rather than one, you can use several threads (basically it runs different code at the same time on different "threads"). Python has a streaming module for simultaneous actions, which may be exactly what you want. The following is sample code with streams enabled.

import threading

def watch_node(node):
    #implement your node watching script here

def watch_in_background(node):
    watcher = threading.Thread(target=watch_node,args=(node))   #initializes a thread that can run the watch_node function in the background, passing the node argument to it
    watcher.start()                                             #tells the thread to start running
    return watcher                                              #returns the thread object just in case you want to use it for something

watch_in_background(<node>)                                     #so this code will now watch the node in the background, allowing you to do other things, like watch multiple nodes