Asyncio zookeeper client (aiozk)

Table of Contents

• Asyncio zookeeper client (aiozk)
  • Status
  • Installation
  • Quick Example
  • Recipes
    • Caution
  • Testing
    • Run tests
    • Testing approach
    • Recipes testing
    • Run some tests directly
  • References

Status

Have no major bugs in client/session/connection, but recipes need more test code to become more robust.

Any help and interest are welcome 😀

Installation

$ pip install aiozk

Quick Example

import asyncio
from aiozk import ZKClient


async def main():
    zk = ZKClient('localhost')
    await zk.start()
    await zk.create('/foo', data=b'bazz', ephemeral=True)
    assert b'bazz' == await zk.get_data('/foo')
    await zk.close()

asyncio.run(main())

Recipes

You may use recipes, similar to zoonado, kazoo, and other libs:

# assuming zk is aiozk.ZKClient

# Lock
async with await zk.recipes.Lock('/path/to/lock').acquire():
    # ... Do some stuff ...
    pass

# Barrier
barrier = zk.recipes.Barrier('/path/to/barrier)
await barrier.create()
await barrier.lift()
await barrier.wait()

# DoubleBarrier
double_barrier = zk.recipes.DoubleBarrier('/path/to/double/barrier', min_participants=4)
await double_barrier.enter(timeout=0.5)
# ...  Do some stuff ...
await double_barrier.leave(timeout=0.5)

You can find full list of recipes provided by aiozk here: aiozk recipes

To understand ideas behind recipes please read this and even more recipes here. Make sure you're familiar with all recipes before doing something new by yourself, especially when it involves more than few zookeeper calls.

Caution

Don't mix different type of recipes at the same znode path. For example, creating a Lock and a DoubleBarrier object at the same path. It may cause undefined behavior 😓

Testing

NB: please ensure that you're using recent docker-compose version. You can get it by running

pip install --user -U docker-compose

Run tests

# you should have access to docker

docker-compose build
./test-runner.sh

Or you can run tests with tox

pip install --user tox tox-docker
tox

Testing approach

Most of tests are integration tests and running on real zookeeper instances. We've chosen zookeeper 3.5 version since it has an ability to dynamic reconfiguration and we're going to do all connecting/reconnecting/watches tests on zk docker cluster as this gives us the ability to restart any server and see what happens.

# first terminal: launch zookeeper cluster
docker-compose rm -fv && docker-compose build zk && docker-compose up --scale zk=7 zk_seed zk

# it will launch cluster in this terminal and remain. last lines should be like this:

zk_6       | Servers: 'server.1=172.23.0.9:2888:3888:participant;0.0.0.0:2181\nserver.2=172.23.0.2:2888:3888:participant;0.0.0.0:2181\nserver.3=172.23.0.3:2888:3888:participant;0.0.0.0:2181\nserver.4=172.23.0.4:2888:3888:participant;0.0.0.0:2181\nserver.5=172.23.0.5:2888:3888:participant;0.0.0.0:2181\nserver.6=172.23.0.7:2888:3888:participant;0.0.0.0:2181'
zk_6       | CONFIG: server.1=172.23.0.9:2888:3888:participant;0.0.0.0:2181
zk_6       | server.2=172.23.0.2:2888:3888:participant;0.0.0.0:2181
zk_6       | server.3=172.23.0.3:2888:3888:participant;0.0.0.0:2181
zk_6       | server.4=172.23.0.4:2888:3888:participant;0.0.0.0:2181
zk_6       | server.5=172.23.0.5:2888:3888:participant;0.0.0.0:2181
zk_6       | server.6=172.23.0.7:2888:3888:participant;0.0.0.0:2181
zk_6       | server.7=172.23.0.6:2888:3888:observer;0.0.0.0:2181
zk_6       |
zk_6       |
zk_6       | Reconfiguring...
zk_6       | ethernal loop
zk_7       | Servers: 'server.1=172.23.0.9:2888:3888:participant;0.0.0.0:2181\nserver.2=172.23.0.2:2888:3888:participant;0.0.0.0:2181\nserver.3=172.23.0.3:2888:3888:participant;0.0.0.0:2181\nserver.4=172.23.0.4:2888:3888:participant;0.0.0.0:2181\nserver.5=172.23.0.5:2888:3888:participant;0.0.0.0:2181\nserver.6=172.23.0.7:2888:3888:participant;0.0.0.0:2181\nserver.7=172.23.0.6:2888:3888:participant;0.0.0.0:2181'
zk_7       | CONFIG: server.1=172.23.0.9:2888:3888:participant;0.0.0.0:2181
zk_7       | server.2=172.23.0.2:2888:3888:participant;0.0.0.0:2181
zk_7       | server.3=172.23.0.3:2888:3888:participant;0.0.0.0:2181
zk_7       | server.4=172.23.0.4:2888:3888:participant;0.0.0.0:2181
zk_7       | server.5=172.23.0.5:2888:3888:participant;0.0.0.0:2181
zk_7       | server.6=172.23.0.7:2888:3888:participant;0.0.0.0:2181
zk_7       | server.7=172.23.0.6:2888:3888:participant;0.0.0.0:2181
zk_7       | server.8=172.23.0.8:2888:3888:observer;0.0.0.0:2181
zk_7       |
zk_7       |
zk_7       | Reconfiguring...
zk_7       | ethernal loop

Run tests in docker:

docker-compose run --no-deps aiozk
# last lines will be about testing results

............lot of lines ommited........
.
----------------------------------------------------------------------
Ran 3 tests in 1.059s

OK

Run tests locally:

# ZK_IP can be something from logs above, like: ZK_HOST=172.21.0.6:2181
ZK_HOST=<ZK_IP> ./venv/bin/pytest

Recipes testing

It seems that usually recipes require several things to be tested:

• That recipe flow is working as expected
• Timeouts: reproduce every timeout with meaningful values (timeout 0.5s and block for 0.6s)

Run some tests directly

Another way to run tests only which you are interested in quickly. Or this is useful when you run tests under the other version of python.

# Run zookeeper container
docker run -p 2181:2181 zookeeper

# Run pytest directly at the development source tree
export ZK_HOST=localhost
pytest -s --log-cli-level=DEBUG aiozk/test/test_barrier.py

References

• It is based on wglass/zoonado implementation