"Handling signal: ttou" message while running DAG in airflow

I don't really want to change worker_refresh_interval or worker_refresh_batch_size without a good reason. An alternative is to set an environment variable:

GUNICORN_CMD_ARGS="--log-level WARNING"

If setting this in a docker-compose.yml file, the following is tested with apache-airflow==1.10.6 with gunicorn==19.9.0:

environment:
    - 'GUNICORN_CMD_ARGS=--log-level WARNING'

If setting this in a Dockerfile, the following is tested with apache-airflow==1.10.6 with gunicorn==19.9.0:

ENV GUNICORN_CMD_ARGS --log-level WARNING

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Credit: answer by amoskaliov

Those messages are expected. The ttou (and ttin) signals are used to refresh gunicorn workers of the webserver so that it picks up DAG changes. You can modify or disable this behavior with the worker_refresh_interval and worker_refresh_batch_size airflow config values.