Concurrency safety

[0x2b3bfa0]

The redisdb fixture runs FLUSHALL after every single test, indiscriminately deleting all the data stored on Redis.

When using an existing Redis instance for all the tests (i.e. with the redis_noproc fixture) and running tests in parallel with pytest-xdist, some tests will fail at random, because all the data is flushed amidst their execution.

pytest-redis/pytest_redis/factories/client.py

Lines 61 to 62 in 21bc790

	yield redis_client
	redis_client.flushall()

What action do you want to perform

$ pytest --numprocesses=2 test.py

import time

from pytest_redis.factories import redis_noproc, redisdb


redis_noproc = redis_noproc()
redis = redisdb("redis_noproc")


def test_one(redis):
    ...


def test_two(redis):
    redis.set("key", b"value")
    time.sleep(1)  # In the meantime, test_one will run, triggering a FLUSHALL.
    assert redis.get("key") == b"value"

What are the results

The test_two will fail, because the test_one will trigger a FLUSHALL as soon as it returns.

What are the expected results

Both tests should succeed.

[0x2b3bfa0]

pytest-dev/pytest-xdist#385 (comment)

The easiest workaround for our use case was using pytest --dist=loadgroup to run all the tests relying on the redis fixture serially:

import pytest
import redis


@pytest.mark.xdist_group(name="redis")
def test_one(redis: redis.Redis):
    ...


@pytest.mark.xdist_group(name="redis")
def test_two(redis: redis.Redis):
    ...