Kazoo

Warnings

• breaking Kazoo frequently updates its supported Python versions, often dropping compatibility with older Python releases. Ensure your environment matches the supported versions to avoid compatibility issues.
  Fix: Refer to the latest Kazoo release notes or documentation for current Python compatibility. For example, Kazoo 2.10.0 dropped support for Python 3.7, now supporting Python 3.8-3.12.
• gotcha KazooClient operates asynchronously. It's crucial to correctly manage the client's lifecycle (start, stop, close) and handle connection state changes (CONNECTED, SUSPENDED, LOST) using listeners or by checking `zk.connected` before performing operations. Operations performed while not connected can lead to errors or unexpected behavior.
  Fix: Implement a connection state listener using `@zk.add_listener` and structure your logic to react to connection events. Ensure `zk.start()` is called and the client has connected before attempting Zookeeper operations.
• gotcha The `hosts` parameter for `KazooClient` expects a comma-separated string of `host:port` pairs (e.g., '127.0.0.1:2181,127.0.0.2:2181'). Using spaces or other delimiters can lead to connection failures.
  Fix: Always provide the Zookeeper host string in the correct `host:port,host:port` format. Validate the string if it's sourced from configuration or environment variables.

Install

• pip install kazoo Install stable version

Imports

• KazooClient

  from kazoo.client import KazooClient

• KazooException

  from kazoo.exceptions import KazooException

Quickstart

This quickstart demonstrates how to connect to Apache ZooKeeper using Kazoo, set up a connection state listener, create an ephemeral node, and retrieve its data. Remember to have a ZooKeeper instance running and set the `ZOOKEEPER_HOSTS` environment variable accordingly.

import os
import time
from kazoo.client import KazooClient
from kazoo.exceptions import KazooException

# Get Zookeeper host(s) from environment variable, e.g., '127.0.0.1:2181,127.0.0.1:2182'
ZOOKEEPER_HOSTS = os.environ.get('ZOOKEEPER_HOSTS', '127.0.0.1:2181')

zk = KazooClient(hosts=ZOOKEEPER_HOSTS)

@zk.add_listener
def my_listener(state):
    """Listener for Zookeeper connection state changes."""
    print(f"Zookeeper state changed: {state}")
    if state == 'CONNECTED':
        print("Successfully connected to Zookeeper!")
    elif state == 'LOST':
        print("Connection to Zookeeper lost. Attempting to reconnect...")
    elif state == 'SUSPENDED':
        print("Connection to Zookeeper suspended. Will attempt to reconnect.")

try:
    print(f"Attempting to connect to Zookeeper at {ZOOKEEPER_HOSTS}...")
    zk.start()
    zk.ensure_path("/my/kazoo/path")
    print("Created /my/kazoo/path if it didn't exist.")

    # Create an ephemeral node that will be deleted when the client disconnects
    node_path = "/my/kazoo/path/ephemeral_node"
    zk.create(node_path, b"hello_kazoo", ephemeral=True, sequence=False)
    print(f"Created ephemeral node: {node_path} with data 'hello_kazoo'")

    data, stat = zk.get(node_path)
    print(f"Retrieved data from {node_path}: {data.decode('utf-8')}, Stat: {stat}")

    # Keep the client alive for a few seconds to observe state changes or for other operations
    time.sleep(5)

except KazooException as e:
    print(f"A Kazoo-specific error occurred: {e}")
except Exception as e:
    print(f"An unexpected error occurred: {e}")
finally:
    if zk.connected:
        zk.stop()
        print("KazooClient stopped.")
    zk.close()
    print("KazooClient closed.")