I had this after reading #12537 and #9047. Currently `DockerOperator`’s `volumes` argument is passed directly to docker-py’s `bind` (aka `docker -v`). But `-v`’s behaviour has long been problematic, and [Docker has been pushing users to the new `--mount` syntax instead](https://docs.docker.com/storage/bind-mounts/#choose-the--v-or---mount-flag). With #12537, it seems like `-v`’s behaviour is also confusing to some Airflow users, so I want to migrate Airflow’s internals to `--mount`.

However, `--mount` has a different syntax to `-v`, and the behaviour is also slightly different, so for compatibility reasons we can’t just do it under the hood. I can think of two possible solutions to this:

A. Deprecate `volumes` altogether and introduce `DockerOperator(mounts=...)`

This will emit a deprecation warning when the user passes `DockerOperator(volumes=...)` to tell them to convert to `DockerOperator(mounts=...)` instead. `volumes` will stay unchanged otherwise, and continue to be passed to bind mounts.

`mounts` will take a list of [`docker.types.Mount`](https://docker-py.readthedocs.io/en/stable/api.html#docker.types.Mount) to describe the mounts. They will be passed directly to the mounts API. Some shorthands could be useful as well, for example:

```python
DockerOperator(
    ...
    mounts=[
        ('/root/data1', './data1'),  # Source and target, default to volume mount.
        ('/root/data2', './data2', 'bind'),  # Bind mount.
    ],
)
```

B. Reuse `volumes` and do introspection to choose between binds and mounts

The `volumes` argument can be augmented to also accept `docker.types.Mount` instances, and internally we’ll do something like

```python
binds = []
mounts = []
for vol in volumes:
    if isinstance(vol, str):
        binds.append(vol)
    elif isintance(vol, docker.types.Mount):
        mounts.append(vol)
    else:
        raise ValueError('...')
if binds:
    warnings.warn('...', DeprecationWarning)
```

and pass the collected lists to binds and mounts respectively.

I’m very interested in hearing thoughts on this.


**Are you willing to submit a PR?**
Yes

**Related Issues**

* #12537: Confusing on the bind syntax.
* #9047: Implement mounting in `DockerSwarmOperator` (it’s a subclass of `DockerOperator`, but the `volumes` option is currently unused).

airflow/providers/docker/example_dags/example_docker_copy_data.py
default_args=default_args,
    schedule_interval=timedelta(minutes=10),
    start_date=days_ago(2),
)
locate_file_cmd = """
    sleep 10
    find {{params.source_location}} -type f  -printf "%f\n" | head -1
"""
t_view = BashOperator(
    task_id="view_file",
    bash_command=locate_file_cmd,
    do_xcom_push=True,
    params={"source_location": "/your/input_dir/path"},
    dag=dag,
)
def is_data_available(*args, **kwargs):
    """Return True if data exists in XCom table for view_file task, false otherwise."""
    ti = kwargs["ti"]
    data = ti.xcom_pull(key=None, task_ids="view_file")
    return not data == ""
t_is_data_available = ShortCircuitOperator(
    task_id="check_if_data_available", python_callable=is_data_available, dag=dag
)
t_move = DockerOperator(
    api_version="1.19",
    docker_url="tcp://localhost:2375",  
    image="centos:latest",
    network_mode="bridge",
    volumes=[
        "/your/host/input_dir/path:/your/input_dir/path",