override_config in multithreaded (parallel) tests execution

[Sajam]

Our test suite that utilizes override_config decorator sometimes fails when we execute tests in parallel (value in config in the test body is different than the one defined in override_config).

My theory is that config in test_A gets overridden in the middle of the test execution by test_B that started after override_config from test_A has been applied.

[SebCorbin]

For parallel testing and overriding, have you considered using another backend that would prevent this from happening (try in-memory for example)? It would also help to know which one you are using in the tests.

[justmobilize]

Which one would work? If they are running on the same machine in parallel, they would still grab the value from the same spot

[rmaciejczyk]

Recently I've run through a pretty similar issue. In my case using the database backend with different spots for each site it turned out it also used the in-memory cache which affected all the sites and messed up config values. For such case you can either turn the cache off

CONSTANCE_DATABASE_CACHE_BACKEND

or (like I do) set a different cache store prefix for each site

CONSTANCE_DATABASE_PREFIX

[brechin]

Currently trying this (using pytest):

@pytest.fixture(scope='session', autouse=True)
def setup_constance_prefix(worker_id):
    """For parallel test-running, use non-overlapping prefixes for Constance config vars to avoid clobbering."""
    if worker_id:
        settings.CONSTANCE_REDIS_PREFIX = 'constance:{}:'.format(worker_id)