How to turn off prefect internal logs when running pytest

[ddehghan]

Hi everyone,

I'm struggling to suppress Prefect's internal logs during tests and would really appreciate any help.

No matter what I try, I keep seeing logs like:

17:23:20.248 | DEBUG   | EventsWorkerThread | prefect._internal.concurrency - Running call get() in thread 'EventsWorkerThread'
17:23:20.248 | DEBUG   | EventsWorkerThread | prefect._internal.concurrency - <WatcherThreadCancelScope, name='get' RUNNING, runtime=0.00> entered
17:23:20.251 | DEBUG   | RunSyncEventLoopThread | prefect._internal.concurrency - Running call coroutine_wrapper() in thread 'RunSyncEventLoopThread'
17:23:20.251 | DEBUG   | RunSyncEventLoopThread | prefect._internal.concurrency - <WatcherThreadCancelScope, name='coroutine_wrapper' RUNNING, runtime=0.00> entered
17:23:20.251 | DEBUG   | RunSyncEventLoopThread | prefect._internal.concurrency - <WatcherThreadCancelScope, name='coroutine_wrapper' COMPLETED, runtime=0.00> exited
17:23:20.251 | DEBUG   | RunSyncEventLoopThread | prefect._internal.concurrency - Scheduling coroutine for call coroutine_wrapper(<dropped>) in running loop <_UnixSelectorEventLoop running=True closed=False debug=False>

Setup:

• Prefect and PostgreSQL are running in Docker.
• Tests are run from my local macOS development machine.

What I’ve tried:

• Using prefect_test_harness(), but it doesn’t work well for me because my tasks involve SQL and rate limiting. SQLite was throwing table lock errors (due to concurrent reads/writes).
• Setting PREFECT_LOGGING_LEVEL=CRITICAL on my local machine — no effect.
• Setting the same inside the Prefect Docker container — also no effect.

Environment:

prefect version
17:30:28.322 | DEBUG   | prefect.profiles - Using profile 'ephemeral'
Version:             3.4.6
API version:         0.8.4
Python version:      3.12.8
Git commit:          d10c6e6a
Built:               Wed, Jun 11, 2025 08:01 PM
OS/Arch:             darwin/arm64
Profile:             ephemeral
Server type:         server
Pydantic version:    2.11.5
Integrations:
   prefect-dask:      0.3.5

From my dev machine:

$ prefect config view --show-defaults | grep LOG
17:30:47.685 | DEBUG   | prefect.profiles - Using profile 'ephemeral'
PREFECT_API_LOG_RETRYABLE_ERRORS='False' (from defaults)
PREFECT_API_SERVICES_EVENT_LOGGER_ENABLED='False' (from defaults)
PREFECT_INTERNAL_LOGGING_LEVEL='CRITICAL' (from env)
PREFECT_LOGGING_COLORS='True' (from defaults)
PREFECT_LOGGING_EXTRA_LOGGERS='[]' (from defaults)
PREFECT_LOGGING_INTERNAL_LEVEL='CRITICAL' (from env)
PREFECT_LOGGING_LEVEL='ERROR' (from env)
PREFECT_LOGGING_LOG_PRINTS='false' (from env)
PREFECT_LOGGING_MARKUP='False' (from defaults)
PREFECT_LOGGING_SERVER_LEVEL='CRITICAL' (from defaults)
PREFECT_LOGGING_SETTINGS_PATH='/Users/david/.prefect/logging.yml' (from defaults)
PREFECT_LOGGING_TO_API_BATCH_INTERVAL='2.0' (from defaults)
PREFECT_LOGGING_TO_API_BATCH_SIZE='4000000' (from defaults)
PREFECT_LOGGING_TO_API_ENABLED='True' (from defaults)
PREFECT_LOGGING_TO_API_MAX_LOG_SIZE='1000000' (from defaults)
PREFECT_LOGGING_TO_API_WHEN_MISSING_FLOW='warn' (from defaults)
PREFECT_RUNNER_SERVER_LOG_LEVEL='ERROR' (from defaults)
PREFECT_SERVER_LOGGING_LEVEL='CRITICAL' (from env)

Has anyone managed to fully suppress these internal DEBUG logs — especially from prefect._internal.concurrency — during tests? Any workaround or configuration trick that actually works?

Thanks!

[zzstoatzz]

hi @ddehghan what about something like this?

@pytest.fixture(autouse=True)
def suppress_prefect_internal_logs():
    """Add this to conftest.py to suppress Prefect internal DEBUG logs."""
    internal_logger = logging.getLogger("prefect._internal")
    original_levels = []
    
    for handler in internal_logger.handlers:
        original_levels.append((handler, handler.level))
        if handler.level == 0:  # Debug handler
            handler.setLevel(logging.CRITICAL)
    
    yield
    
    for handler, level in original_levels:
        handler.setLevel(level)