potiuk commented on a change in pull request #16170:
URL: https://github.com/apache/airflow/pull/16170#discussion_r642123454
##########
File path: docs/docker-stack/entrypoint.rst
##########
@@ -120,8 +120,82 @@ takes precedence over the
:envvar:`AIRFLOW__CORE__SQL_ALCHEMY_CONN` variable.
For newer versions, the ``airflow db check`` command is used, which means that
a ``select 1 as is_alive;`` query
is executed. This also means that you can keep your password in secret backend.
+Waits for celery broker connection
+----------------------------------
+
+In case Postgres or MySQL DB is used, and one of the ``scheduler``,
``celery``, ``worker``, or ``flower``
+commands are used the entrypoint will wait until the celery broker DB
connection is available.
+
+The script detects backend type depending on the URL schema and assigns
default port numbers if not specified
+in the URL. Then it loops until connection to the host/port specified can be
established
+It tries :envvar:`CONNECTION_CHECK_MAX_COUNT` times and sleeps
:envvar:`CONNECTION_CHECK_SLEEP_TIME` between checks.
+To disable check, set ``CONNECTION_CHECK_MAX_COUNT=0``.
+
+Supported schemes:
+
+* ``amqp(s)://`` (rabbitmq) - default port 5672
+* ``redis://`` - default port 6379
+* ``postgres://`` - default port 5432
+* ``mysql://`` - default port 3306
+
+Waiting for connection involves checking if a matching port is open.
+The host information is derived from the variables
:envvar:`AIRFLOW__CELERY__BROKER_URL` and
+:envvar:`AIRFLOW__CELERY__BROKER_URL_CMD`. If
:envvar:`AIRFLOW__CELERY__BROKER_URL_CMD` variable
+is passed to the container, it is evaluated as a command to execute and result
of this evaluation is used
+as :envvar:`AIRFLOW__CELERY__BROKER_URL`. The
:envvar:`AIRFLOW__CELERY__BROKER_URL_CMD` variable
+takes precedence over the :envvar:`AIRFLOW__CELERY__BROKER_URL` variable.
+
+.. _entrypoint:commands:
+
+Executing commands
+------------------
+
+If first argument equals to "bash" - you are dropped to a bash shell or you
can executes bash command
+if you specify extra arguments. For example:
+
+.. code-block:: bash
+
+ docker run -it apache/airflow:2.1.0-python3.6 bash -c "ls -la"
+ total 16
+ drwxr-xr-x 4 airflow root 4096 Jun 5 18:12 .
+ drwxr-xr-x 1 root root 4096 Jun 5 18:12 ..
+ drwxr-xr-x 2 airflow root 4096 Jun 5 18:12 dags
+ drwxr-xr-x 2 airflow root 4096 Jun 5 18:12 logs
+
+If first argument is equal to ``python`` - you are dropped in python shell or
python commands are executed if
+you pass extra parameters. For example:
+
+.. code-block:: bash
+
+ > docker run -it apache/airflow:2.1.0-python3.6 python -c "print('test')"
+ test
+
+If first argument equals to "airflow" - the rest of the arguments is treated
as an airflow command
+to execute. Example:
+
+.. code-block:: bash
+
+ docker run -it apache/airflow:2.1.0-python3.6 airflow webserver
+
+If there are any other arguments - they are simply passed to the "airflow"
command
+
+.. code-block:: bash
+
+ > docker run -it apache/airflow:2.1.0-python3.6 version
+ 2.1.0
+
+Additional quick test options
+-----------------------------
+
+The options below are mostly used for quick testing the image - for example
with
+quick-start docker-compose or when you want to perform a local test with new
packages
+added. They are not supposed to be run in the production environment as they
add additional
+overhead for execution of additional commands. Those options in production
should be realized
+either as maintenance operations on the database or should be embedded in teh
custom image used
Review comment:
```suggestion
either as maintenance operations on the database or should be embedded in
the custom image used
```
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