.. Licensed to the Apache Software Foundation (ASF) under one
   or more contributor license agreements.  See the NOTICE file
   distributed with this work for additional information
   regarding copyright ownership.  The ASF licenses this file
   to you under the Apache License, Version 2.0 (the
   "License"); you may not use this file except in compliance
   with the License.  You may obtain a copy of the License at

..   http://www.apache.org/licenses/LICENSE-2.0

.. Unless required by applicable law or agreed to in writing,
   software distributed under the License is distributed on an
   "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   KIND, either express or implied.  See the License for the
   specific language governing permissions and limitations
   under the License.


Upgrading to Airflow 2.0+
-------------------------

.. contents:: :local:

Apache Airflow 2.0 is a major release and the purpose of this document is to assist
users to migrate from Airflow 1.10.x to Airflow 2.0.

Step 1: Upgrade to Python 3
'''''''''''''''''''''''''''

Airflow 1.10 will be the last release series to support Python 2. Airflow 2.0.0 will
require Python 3.6+ and at this point in time has been tested with Python versions 3.6, 3.7,
and 3.8, but does not yet support Python 3.9.

If you have a specific task that still requires Python 2 then you can use the :class:`~airflow.operators.python.PythonVirtualenvOperator` or the ``KubernetesPodOperator`` for this.

For a list of breaking changes between Python 2 and Python 3, please refer to this
[handy blog](https://blog.couchbase.com/tips-and-tricks-for-upgrading-from-python-2-to-python-3/)
from the CouchBaseDB team.


Step 2: Upgrade to Airflow 1.10.14 (a.k.a our "bridge" release)
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

To minimize friction for users upgrading from Airflow 1.10 to Airflow 2.0 and beyond, Airflow 1.10.14 "a bridge release" has
been created. This is intended to be the final 1.10 feature release. Airflow 1.10.14 includes support for various features
that have been backported from Airflow 2.0 to make it easy for users to test their Airflow
environment before upgrading to Airflow 2.0.

We strongly recommend that all users upgrading to Airflow 2.0, first
upgrade to Airflow 1.10.14 and test their Airflow deployment and only then upgrade to Airflow 2.0. After the
Airflow 2.0 GA (General Availability) release, it is expected that all future Airflow development would be
based on Airflow 2.0. The Airflow 1.10.x release tree will be supported for a limited time after the GA
release of Airflow 2.0.

Features in 1.10.14 include:

1. Most breaking DAG and architecture changes of Airflow 2.0 have been backported to Airflow 1.10.14. This backward-compatibility does not mean
that 1.10.14 will process these DAGs the same way as Airflow 2.0. Instead, this means that most Airflow 2.0
compatible DAGs will work in Airflow 1.10.14. This backport will give users time to modify their DAGs over time
without any service disruption.

2. We have also backported the updated Airflow 2.0 CLI commands to Airflow 1.10.4, so that users can modify their scripts
to be compatible with Airflow 2.0 before the upgrade.

3. For users of the KubernetesExecutor, we have backported the ``pod_template_file`` capability for the KubernetesExecutor
as well as a script that will generate a ``pod_template_file`` based on your ``airflow.cfg`` settings. To generate this file
simply run the following command:

.. code-block:: bash

     airflow generate_pod_template -o <output file path>

Once you have performed this step, simply write out the file path to this file in the ``pod_template_file`` config of the ``kubernetes``
section of your ``airflow.cfg``

Step 3: Install and run the Upgrade check scripts
'''''''''''''''''''''''''''''''''''''''''''''''''

After upgrading to Airflow 1.10.14, we recommend that you install the "upgrade check" scripts. These scripts will read through your ``airflow.cfg`` and all of your DAGs and will give a detailed report of all changes required before upgrading. We are testing this script diligently, and our goal is that any Airflow setup that can pass these tests will be able to upgrade to 2.0 without any issues.

.. code-block:: bash

     pip install apache-airflow-upgrade-check

Once this is installed, please run the upgrade check script.

.. code-block:: bash

     airflow upgrade_check

More details about this process are here :ref:`Upgrade Check Scripts<upgrade-check>`.


Step 4: Import Operators from Backport Providers
''''''''''''''''''''''''''''''''''''''''''''''''

Now that you are set up in Airflow 1.10.14 with Python a 3.6+ environment, you are ready to start porting your DAGs to Airflow 2.0 compliance!

The most important step in this transition is also the easiest step to do in pieces. All Airflow 2.0 operators are backwards compatible with Airflow 1.10
using the backport provider packages. In your own time, you can transition to using these backport-providers
by pip installing the provider via ``pypi`` and changing the import path.

For example: While historically you might have imported the DockerOperator in this fashion:

.. code-block:: python

    from airflow.operators.docker_operator import DockerOperator

You would now run this command to install the provider:

.. code-block:: bash

    pip install apache-airflow-backport-providers-docker


and then import the operator with this path:

.. code-block:: python

    from airflow.providers.docker.operators.docker import DockerOperator

Please note that the backport provider packages are just backports of the provider packages compatible with Airflow 2.0.
For example:

.. code-block:: bash

    pip install 'apache-airflow[docker]'

automatically installs the ``apache-airflow-providers-docker`` package.
But you can manage/upgrade/remove provider packages separately from the Airflow core.

After you upgrade to Apache Airflow 2.0, those provider packages are installed automatically when you install Airflow with extras.
Several of the providers (http, ftp, sqlite, imap) will also be installed automatically when you install Airflow even without extras.
You can read more about providers at :doc:`apache-airflow-providers:index`.

Step 5: Upgrade Airflow DAGs
''''''''''''''''''''''''''''

**Change to undefined variable handling in templates**

Prior to Airflow 2.0 Jinja Templates would permit the use of undefined variables. They would render as an
empty string, with no indication to the user an undefined variable was used. With this release, any template
rendering involving undefined variables will fail the task, as well as displaying an error in the UI when
rendering.

The behavior can be reverted when instantiating a DAG.

.. code-block:: python

    import jinja2

    dag = DAG('simple_dag', template_undefined=jinja2.Undefined)

Alternatively, it is also possible to override each Jinja Template variable on an individual basis
by using the ``| default`` Jinja filter as shown below.

.. code-block:: python

    {{ a | default(1) }}


**Changes to the KubernetesPodOperator**

Much like the ``KubernetesExecutor``, the ``KubernetesPodOperator`` will no longer take Airflow custom classes and will
instead expect either a pod_template yaml file, or ``kubernetes.client.models`` objects.

The one notable exception is that we will continue to support the ``airflow.kubernetes.secret.Secret`` class.

Whereas previously a user would import each individual class to build the pod as so:

.. code-block:: python

    from airflow.kubernetes.pod import Port
    from airflow.kubernetes.volume import Volume
    from airflow.kubernetes.secret import Secret
    from airflow.kubernetes.volume_mount import VolumeMount


    volume_config = {
        'persistentVolumeClaim': {
            'claimName': 'test-volume'
        }
    }
    volume = Volume(name='test-volume', configs=volume_config)
    volume_mount = VolumeMount('test-volume',
                               mount_path='/root/mount_file',
                               sub_path=None,
                               read_only=True)

    port = Port('http', 80)
    secret_file = Secret('volume', '/etc/sql_conn', 'airflow-secrets', 'sql_alchemy_conn')
    secret_env = Secret('env', 'SQL_CONN', 'airflow-secrets', 'sql_alchemy_conn')

    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo", "10"],
        labels={"foo": "bar"},
        secrets=[secret_file, secret_env],
        ports=[port],
        volumes=[volume],
        volume_mounts=[volume_mount],
        name="airflow-test-pod",
        task_id="task",
        affinity=affinity,
        is_delete_operator_pod=True,
        hostnetwork=False,
        tolerations=tolerations,
        configmaps=configmaps,
        init_containers=[init_container],
        priority_class_name="medium",
    )


Now the user can use the ``kubernetes.client.models`` class as a single point of entry for creating all k8s objects.

.. code-block:: python

    from kubernetes.client import models as k8s
    from airflow.kubernetes.secret import Secret


    configmaps = ['test-configmap-1', 'test-configmap-2']

    volume = k8s.V1Volume(
        name='test-volume',
        persistent_volume_claim=k8s.V1PersistentVolumeClaimVolumeSource(claim_name='test-volume'),
    )

    port = k8s.V1ContainerPort(name='http', container_port=80)
    secret_file = Secret('volume', '/etc/sql_conn', 'airflow-secrets', 'sql_alchemy_conn')
    secret_env = Secret('env', 'SQL_CONN', 'airflow-secrets', 'sql_alchemy_conn')
    secret_all_keys = Secret('env', None, 'airflow-secrets-2')
    volume_mount = k8s.V1VolumeMount(
        name='test-volume', mount_path='/root/mount_file', sub_path=None, read_only=True
    )

    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo", "10"],
        labels={"foo": "bar"},
        secrets=[secret_file, secret_env],
        ports=[port],
        volumes=[volume],
        volume_mounts=[volume_mount],
        name="airflow-test-pod",
        task_id="task",
        is_delete_operator_pod=True,
        hostnetwork=False)


We decided to keep the Secret class as users seem to really like that simplifies the complexity of mounting
Kubernetes secrets into workers.

For a more detailed list of changes to the KubernetesPodOperator API, please read the section in the Appendix titled "Changed Parameters for the KubernetesPodOperator"


**Change default value for dag_run_conf_overrides_params**

DagRun configuration dictionary will now by default overwrite params dictionary. If you pass some key-value pairs
through ``airflow dags backfill -c`` or ``airflow dags trigger -c``, the key-value pairs will
override the existing ones in params. You can revert this behaviour by setting ``dag_run_conf_overrides_params`` to ``False``
in your ``airflow.cfg``.

**DAG discovery safe mode is now case insensitive**

When ``DAG_DISCOVERY_SAFE_MODE`` is active, Airflow will now filter all files that contain the string ``airflow`` and ``dag``
in a case insensitive mode. This is being changed to better support the new ``@dag`` decorator.

**Change to Permissions**

The DAG-level permission actions, ``can_dag_read`` and ``can_dag_edit`` are deprecated as part of Airflow 2.0. They are
being replaced with ``can_read`` and ``can_edit``. When a role is given DAG-level access, the resource name (or "view menu",
in Flask App-Builder parlance) will now be prefixed with ``DAG:``. So the action ``can_dag_read`` on ``example_dag_id``, is
now represented as ``can_read`` on ``DAG:example_dag_id``.
There is a special view called ``DAGs`` (it was called ``all_dags`` in versions 1.10.x) which allows the role to access
all the DAGs. The default ``Admin``, ``Viewer``, ``User``, ``Op`` roles can all access the ``DAGs`` view.

*As part of running ``airflow db upgrade``, existing permissions will be migrated for you.*

When DAGs are initialized with the ``access_control`` variable set, any usage of the old permission names will automatically be updated in the database, so this won't be a breaking change. A DeprecationWarning will be raised.

**Drop legacy UI in favor of FAB RBAC UI**

.. warning::
    Breaking change

    Previously we were using two versions of UI, which were hard to maintain as we need to implement/update the same feature
    in both versions. With this release we've removed the older UI in favor of Flask App Builder RBAC UI. No need to set the
    RBAC UI explicitly in the configuration now as this is the only default UI. We did it to avoid
    the huge maintenance burden of two independent user interfaces

Please note that that custom auth backends will need re-writing to target new FAB based UI.

As part of this change, a few configuration items in ``[webserver]`` section are removed and no longer applicable,
including ``authenticate``, ``filter_by_owner``, ``owner_mode``, and ``rbac``.

Before upgrading to this release, we recommend activating the new FAB RBAC UI. For that, you should set
the ``rbac`` options  in ``[webserver]`` in the ``airflow.cfg`` file to ``true``

.. code-block:: ini

    [webserver]
    rbac = true

In order to login to the interface, you need to create an administrator account.

Assuming you have already installed Airflow 1.10.14, you can create a user with
Airflow 2.0 CLI command syntax ``airflow users create``.
You don't need to make changes to the configuration file as the FAB RBAC UI is
the only supported UI.

.. code-block:: bash

    airflow users create \
        --role Admin \
        --username admin \
        --firstname FIRST_NAME \
        --lastname LAST_NAME \
        --email EMAIL@example.org

**Breaking Change in OAuth**

The ``flask-ouathlib`` has been replaced with ``authlib`` because ``flask-outhlib`` has
been deprecated in favor of ``authlib``.
The Old and New provider configuration keys that have changed are as follows

======================== ==================
Old Keys                 New keys
======================== ==================
``consumer_key``         ``client_id``
``consumer_secret``      ``client_secret``
``base_url``             ``api_base_url``
``request_token_params`` ``client_kwargs``
======================== ==================

For more information, visit https://flask-appbuilder.readthedocs.io/en/latest/security.html#authentication-oauth


Step 6: Upgrade Configuration settings
'''''''''''''''''''''''''''''''''''''''''''

Airflow 2.0 is stricter with respect to expectations on configuration data and requires explicit
specifications of configuration values in more cases rather than defaulting to a generic value.

Some of these are detailed in the Upgrade Check guide, but a significant area of change is with
respect to the Kubernetes Executor. This is called out below for users of the Kubernetes Executor.

**Upgrade KubernetesExecutor settings**

*The KubernetesExecutor Will No Longer Read from the airflow.cfg for Base Pod Configurations.*

In Airflow 2.0, the KubernetesExecutor will require a base pod template written in yaml. This file can exist
anywhere on the host machine and will be linked using the ``pod_template_file`` configuration in the ``airflow.cfg`` file.
You can create a ``pod_template_file`` by running the following command:  ``airflow generate_pod_template``

The ``airflow.cfg`` will still accept values for the ``worker_container_repository``, the ``worker_container_tag``, and
the default namespace.

The following ``airflow.cfg`` values will be deprecated::

    worker_container_image_pull_policy
    airflow_configmap
    airflow_local_settings_configmap
    dags_in_image
    dags_volume_subpath
    dags_volume_mount_point
    dags_volume_claim
    logs_volume_subpath
    logs_volume_claim
    dags_volume_host
    logs_volume_host
    env_from_configmap_ref
    env_from_secret_ref
    git_repo
    git_branch
    git_sync_depth
    git_subpath
    git_sync_rev
    git_user
    git_password
    git_sync_root
    git_sync_dest
    git_dags_folder_mount_point
    git_ssh_key_secret_name
    git_ssh_known_hosts_configmap_name
    git_sync_credentials_secret
    git_sync_container_repository
    git_sync_container_tag
    git_sync_init_container_name
    git_sync_run_as_user
    worker_service_account_name
    image_pull_secrets
    gcp_service_account_keys
    affinity
    tolerations
    run_as_user
    fs_group
    [kubernetes_node_selectors]
    [kubernetes_annotations]
    [kubernetes_environment_variables]
    [kubernetes_secrets]
    [kubernetes_labels]


**The ``executor_config`` Will Now Expect a ``kubernetes.client.models.V1Pod`` Class When Launching Tasks**

In Airflow 1.10.x, users could modify task pods at runtime by passing a dictionary to the ``executor_config`` variable.
Users will now have full access the Kubernetes API via the ``kubernetes.client.models.V1Pod``.

While in the deprecated version a user would mount a volume using the following dictionary:

.. code-block:: python

    second_task = PythonOperator(
        task_id="four_task",
        python_callable=test_volume_mount,
        executor_config={
            "KubernetesExecutor": {
                "volumes": [
                    {
                        "name": "example-kubernetes-test-volume",
                        "hostPath": {"path": "/tmp/"},
                    },
                ],
                "volume_mounts": [
                    {
                        "mountPath": "/foo/",
                        "name": "example-kubernetes-test-volume",
                    },
                ]
            }
        }
    )

In the new model a user can accomplish the same thing using the following code under the ``pod_override`` key:

.. code-block:: python

    from kubernetes.client import models as k8s

    second_task = PythonOperator(
        task_id="four_task",
        python_callable=test_volume_mount,
        executor_config={"pod_override": k8s.V1Pod(
            spec=k8s.V1PodSpec(
                containers=[
                    k8s.V1Container(
                        name="base",
                        volume_mounts=[
                            k8s.V1VolumeMount(
                                mount_path="/foo/",
                                name="example-kubernetes-test-volume"
                            )
                        ]
                    )
                ],
                volumes=[
                    k8s.V1Volume(
                        name="example-kubernetes-test-volume",
                        host_path=k8s.V1HostPathVolumeSource(
                            path="/tmp/"
                        )
                    )
                ]
            )
        )
        }
    )

For Airflow 2.0, the traditional ``executor_config`` will continue operation with a deprecation warning,
but will be removed in a future version.


Step 7: Upgrade to Airflow 2.0
'''''''''''''''''''''''''''''''

After running the upgrade checks as described above, installing the backported providers, modifying
the DAGs to be compatible, and updating the configuration settings, you should be ready to upgrade to Airflow 2.0.

A final run of the upgrade checks is always a good idea to make sure you have missed anything. At
this stage the problems detected should be either be zero or minimal which you plan to fix after
upgrading the Airflow version.

At this point, just follow the standard Airflow version upgrade process:

* Make sure your Airflow meta database is backed up
* Pause all the DAGs and make sure there is nothing actively running

  * The reason to pause DAGs is to make sure that nothing is actively being written to the database during the database upgrade which will follow in a later step.
  * To be extra careful, it is best to have a database backup after the DAGs have been paused.

* Install / upgrade the Airflow version to the 2.0 version of choice
* Make sure to install the right providers

  * This can be done by using the "extras" option as part of the Airflow installation, or by individually installing the providers.
  * Please note that you may have to uninstall the backport providers before installing the new providers, if you are installing using pip. This would not apply if you are installing using an Airflow Docker image with a set of specified requirements, where the change automatically gets a fresh set of modules.
  * You can read more about providers at :doc:`apache-airflow-providers:index`.

* Upgrade the Airflow meta database using ``airflow db upgrade``.

  * The above command may be unfamiliar, since it is shown using the Airflow 2.0 CLI syntax.
  * The database upgrade may modify the database schema as needed and also map the existing data to be compliant with the update database schema.

  .. note::

      The database upgrade may take a while depending on the number of DAGs in the database and the volume of history
      stored in the database for task history, xcom variables, etc.
      In our testing, we saw that performing the Airflow database upgrade from Airflow 1.10.14 to Airflow 2.0
      took between two to three minutes on an Airflow database on PostgreSQL with around 35,000 task instances and
      500 DAGs.
      For a faster database upgrade and for better overall performance, it is recommended that you periodically archive
      the old historical elements which are no longer of value.

* Restart Airflow Scheduler, Webserver, and Workers


Appendix
''''''''

Changed Parameters for the KubernetesPodOperator
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

**Port has migrated from a List[Port] to a List[V1ContainerPort]**

Before:

.. code-block:: python

    from airflow.kubernetes.pod import Port
    port = Port('http', 80)
    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo 10"],
        ports=[port],
        task_id="task",
    )

After:

.. code-block:: python

    from kubernetes.client import models as k8s
    port = k8s.V1ContainerPort(name='http', container_port=80)
    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo 10"],
        ports=[port],
        task_id="task",
    )

**Volume_mounts have migrated from a List[VolumeMount] to a List[V1VolumeMount]**

Before:

.. code-block:: python

    from airflow.kubernetes.volume_mount import VolumeMount
    volume_mount = VolumeMount('test-volume',
                               mount_path='/root/mount_file',
                               sub_path=None,
                               read_only=True)
    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo 10"],
        volume_mounts=[volume_mount],
        task_id="task",
    )

After:

.. code-block:: python

    from kubernetes.client import models as k8s
    volume_mount = k8s.V1VolumeMount(
        name='test-volume', mount_path='/root/mount_file', sub_path=None, read_only=True
    )
    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo 10"],
        volume_mounts=[volume_mount],
        task_id="task",
    )


**Volume has migrated from a List[Volume] to a List[V1Volume]**

Before:

.. code-block:: python

    from airflow.kubernetes.volume import Volume

    volume_config = {
        'persistentVolumeClaim': {
            'claimName': 'test-volume'
    }
    }
    volume = Volume(name='test-volume', configs=volume_config)
    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo 10"],
        volumes=[volume],
        task_id="task",
    )

After:

.. code-block:: python

    from kubernetes.client import models as k8s
    volume = k8s.V1Volume(
        name='test-volume',
        persistent_volume_claim=k8s.V1PersistentVolumeClaimVolumeSource(claim_name='test-volume'),
    )
    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo 10"],
        volumes=[volume],
        task_id="task",
    )

**env_vars has migrated from a Dict to a List[V1EnvVar]**

Before:

.. code-block:: python

    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo 10"],
        env_vars={"ENV1": "val1", "ENV2": "val2"},
        task_id="task",
    )

After:

.. code-block:: python

    from kubernetes.client import models as k8s

    env_vars = [
        k8s.V1EnvVar(
            name="ENV1",
            value="val1"
        ),
        k8s.V1EnvVar(
            name="ENV2",
            value="val2"
        )]

    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo 10"],
        env_vars=env_vars,
        task_id="task",
    )


**PodRuntimeInfoEnv has been removed**

PodRuntimeInfoEnv can now be added to the ``env_vars`` variable as a ``V1EnvVarSource``

Before:

.. code-block:: python

    from airflow.kubernetes.pod_runtime_info_env import PodRuntimeInfoEnv

    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo 10"],
        pod_runtime_info_envs=[PodRuntimeInfoEnv("ENV3", "status.podIP")],
        task_id="task",
    )

After:

.. code-block:: python

    from kubernetes.client import models as k8s

    env_vars = [
        k8s.V1EnvVar(
            name="ENV3",
            value_from=k8s.V1EnvVarSource(
                field_ref=k8s.V1ObjectFieldSelector(
                    field_path="status.podIP"
                )
            )
        )
    ]

    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo 10"],
        env_vars=env_vars,
        task_id="task",
    )

**configmaps has been removed**

Configmaps can now be added to the ``env_from`` variable as a ``V1EnvVarSource``

Before:

.. code-block:: python

    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo 10"],
        configmaps=['test-configmap'],
        task_id="task"
    )


After:

.. code-block:: python

    from kubernetes.client import models as k8s

    configmap ="test-configmap"
    env_from = [k8s.V1EnvFromSource(
                    config_map_ref=k8s.V1ConfigMapEnvSource(
                        name=configmap
                    )
                )]

    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo 10"],
        env_from=env_from,
        task_id="task"
    )


**Resources has migrated from a Dict to a V1ResourceRequirements**

Before:

.. code-block:: python

    resources = {
        'limit_cpu': 0.25,
        'limit_memory': '64Mi',
        'limit_ephemeral_storage': '2Gi',
        'request_cpu': '250m',
        'request_memory': '64Mi',
        'request_ephemeral_storage': '1Gi',
    }
    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo 10"],
        labels={"foo": "bar"},
        name="test",
        task_id="task" + self.get_current_task_name(),
        in_cluster=False,
        do_xcom_push=False,
        resources=resources,
    )

After:

.. code-block:: python

    from kubernetes.client import models as k8s

    resources=k8s.V1ResourceRequirements(
        requests={
            'memory': '64Mi',
            'cpu': '250m',
            'ephemeral-storage': '1Gi'
        },
        limits={
            'memory': '64Mi',
            'cpu': 0.25,
            'nvidia.com/gpu': None,
            'ephemeral-storage': '2Gi'
        }
    )
    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo 10"],
        labels={"foo": "bar"},
        name="test-" + str(random.randint(0, 1000000)),
        task_id="task" + self.get_current_task_name(),
        in_cluster=False,
        do_xcom_push=False,
        resources=resources,
    )


**image_pull_secrets has migrated from a String to a List[k8s.V1LocalObjectReference]**

Before:

.. code-block:: python

    k = KubernetesPodOperator(
        namespace='default',
        image="ubuntu:16.04",
        cmds=["bash", "-cx"],
        arguments=["echo 10"],
        name="test",
        task_id="task",
        image_pull_secrets="fake-secret",
        cluster_context='default'
    )

After:

.. code-block:: python

    quay_k8s = KubernetesPodOperator(
        namespace='default',
        image='quay.io/apache/bash',
        image_pull_secrets=[k8s.V1LocalObjectReference('testquay')],
        cmds=["bash", "-cx"],
        name="airflow-private-image-pod",
        task_id="task-two",
    )


Migration Guide from Experimental API to Stable API v1
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

In Airflow 2.0, we added the new REST API. Experimental API still works, but support may be dropped in the future.

The experimental API however does not require authentication, so it is disabled by default. You need to explicitly enable the experimental API if you want to use it.
If your application is still using the experimental API, you should **seriously** consider migrating to the stable API.

The stable API exposes many endpoints available through the webserver. Here are the
differences between the two endpoints that will help you migrate from the
experimental REST API to the stable REST API.

**Base Endpoint**

The base endpoint for the stable API v1 is ``/api/v1/``. You must change the
experimental base endpoint from ``/api/experimental/`` to ``/api/v1/``.
The table below shows the differences:

================================= ==================================================================================== ==================================================================================
Purpose                           Experimental REST API Endpoint                                                       Stable REST API Endpoint
================================= ==================================================================================== ==================================================================================
Create a DAGRuns(POST)            ``/api/experimental/dags/<DAG_ID>/dag_runs``                                         ``/api/v1/dags/{dag_id}/dagRuns``
List DAGRuns(GET)                 ``/api/experimental/dags/<DAG_ID>/dag_runs``                                         ``/api/v1/dags/{dag_id}/dagRuns``
Check Health status(GET)          ``/api/experimental/test``                                                           ``/api/v1/health``
Task information(GET)             ``/api/experimental/dags/<DAG_ID>/tasks/<TASK_ID>``                                  ``/api/v1//dags/{dag_id}/tasks/{task_id}``
TaskInstance public variable(GET) ``/api/experimental/dags/<DAG_ID>/dag_runs/<string:execution_date>/tasks/<TASK_ID>`` ``/api/v1/dags/{dag_id}/dagRuns/{dag_run_id}/taskInstances/{task_id}``
Pause DAG(PATCH)                  ``/api/experimental/dags/<DAG_ID>/paused/<string:paused>``                           ``/api/v1/dags/{dag_id}``
Information of paused DAG(GET)    ``/api/experimental/dags/<DAG_ID>/paused``                                           ``/api/v1/dags/{dag_id}``
Latest DAG Runs(GET)              ``/api/experimental/latest_runs``                                                    ``/api/v1/dags/{dag_id}/dagRuns``
Get all pools(GET)                ``/api/experimental/pools``                                                          ``/api/v1/pools``
Create a pool(POST)               ``/api/experimental/pools``                                                          ``/api/v1/pools``
Delete a pool(DELETE)             ``/api/experimental/pools/<string:name>``                                            ``/api/v1/pools/{pool_name}``
DAG Lineage(GET)                  ``/api/experimental/lineage/<DAG_ID>/<string:execution_date>/``                      ``/api/v1/dags/{dag_id}/dagRuns/{dag_run_id}/taskInstances/{task_id}/xcomEntries``
================================= ==================================================================================== ==================================================================================


This endpoint ``/api/v1/dags/{dag_id}/dagRuns`` also allows you to filter dag_runs with parameters such as ``start_date``, ``end_date``, ``execution_date`` etc in the query string.
Therefore the operation previously performed by this endpoint:

.. code-block:: bash

    /api/experimental/dags/<string:dag_id>/dag_runs/<string:execution_date>

can now be handled with filter parameters in the query string.
Getting information about latest runs can be accomplished with the help of
filters in the query string of this endpoint(``/api/v1/dags/{dag_id}/dagRuns``). Please check the Stable API
reference documentation for more information


Changes to Exception handling for from DAG callbacks
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Exception from DAG callbacks used to crash the Airflow Scheduler. As part
of our efforts to make the Scheduler more performant and reliable, we have changed this behavior to log the exception
instead. On top of that, a new dag.callback_exceptions counter metric has
been added to help better monitor callback exceptions.


Airflow CLI changes in 2.0
^^^^^^^^^^^^^^^^^^^^^^^^^^

The Airflow CLI has been organized so that related commands are grouped together as subcommands,
which means that if you use these commands in your scripts, you have to make changes to them.

This section describes the changes that have been made, and what you need to do to update your scripts.
The ability to manipulate users from the command line has been changed. ``airflow create_user``,  ``airflow delete_user``
and ``airflow list_users`` has been grouped to a single command ``airflow users`` with optional flags ``create``, ``list`` and ``delete``.
The ``airflow list_dags`` command is now ``airflow dags list``, ``airflow pause`` is ``airflow dags pause``, etc.

In Airflow 1.10 and 2.0 there is an ``airflow config`` command but there is a difference in behavior. In Airflow 1.10,
it prints all config options while in Airflow 2.0, it's a command group. ``airflow config`` is now ``airflow config list``.
You can check other options by running the command ``airflow config --help``

For a complete list of updated CLI commands, see https://airflow.apache.org/cli.html.

You can learn about the commands by running ``airflow --help``. For example to get help about the ``celery`` group command,
you have to run the help command: ``airflow celery --help``.

============================= ================================= =====================
Old command                   New command                       Group
============================= ================================= =====================
``airflow worker``            ``airflow celery worker``         ``celery``
``airflow flower``            ``airflow celery flower``         ``celery``
``airflow trigger_dag``       ``airflow dags trigger``          ``dags``
``airflow delete_dag``        ``airflow dags delete``           ``dags``
``airflow show_dag``          ``airflow dags show``             ``dags``
``airflow list_dag``          ``airflow dags list``             ``dags``
``airflow dag_status``        ``airflow dags status``           ``dags``
``airflow backfill``          ``airflow dags backfill``         ``dags``
``airflow list_dag_runs``     ``airflow dags list-runs``        ``dags``
``airflow pause``             ``airflow dags pause``            ``dags``
``airflow unpause``           ``airflow dags unpause``          ``dags``
``airflow next_execution``    ``airflow dags next-execution``   ``dags``
``airflow test``              ``airflow tasks test``            ``tasks``
``airflow clear``             ``airflow tasks clear``           ``tasks``
``airflow list_tasks``        ``airflow tasks list``            ``tasks``
``airflow task_failed_deps``  ``airflow tasks failed-deps``     ``tasks``
``airflow task_state``        ``airflow tasks state``           ``tasks``
``airflow run``               ``airflow tasks run``             ``tasks``
``airflow render``            ``airflow tasks render``          ``tasks``
``airflow initdb``            ``airflow db init``               ``db``
``airflow resetdb``           ``airflow db reset``              ``db``
``airflow upgradedb``         ``airflow db upgrade``            ``db``
``airflow checkdb``           ``airflow db check``              ``db``
``airflow shell``             ``airflow db shell``              ``db``
``airflow pool``              ``airflow pools``                 ``pools``
``airflow create_user``       ``airflow users create``          ``users``
``airflow delete_user``       ``airflow users delete``          ``users``
``airflow list_users``        ``airflow users list``            ``users``
``airflow rotate_fernet_key`` ``airflow rotate-fernet-key``
``airflow sync_perm``         ``airflow sync-perm``
============================= ================================= =====================


**Example Usage for the ``users`` group**

To create a new user:

.. code-block:: bash

    airflow users create --username jondoe --lastname doe --firstname jon --email jdoe@apache.org --role Viewer --password test

To list users:

.. code-block:: bash

    airflow users list

To delete a user:

.. code-block:: bash

    airflow users delete --username jondoe


To add a user to a role:

.. code-block:: bash

    airflow users add-role --username jondoe --role Public

To remove a user from a role:

.. code-block:: bash

    airflow users remove-role --username jondoe --role Public


**Use exactly single character for short option style change in CLI**

For Airflow short option, use exactly one single character. New commands are available according to the following table:

==================================================== ====================================================
Old command                                          New command
==================================================== ====================================================
``airflow (dags\|tasks\|scheduler) [-sd, --subdir]`` ``airflow (dags\|tasks\|scheduler) [-S, --subdir]``
``airflow test [-dr, --dry_run]``                    ``airflow tasks test [-n, --dry-run]``
``airflow test [-tp, --task_params]``                ``airflow tasks test [-t, --task-params]``
``airflow test [-pm, --post_mortem]``                ``airflow tasks test [-m, --post-mortem]``
``airflow run [-int, --interactive]``                ``airflow tasks run [-N, --interactive]``
``airflow backfill [-dr, --dry_run]``                ``airflow dags backfill [-n, --dry-run]``
``airflow clear [-dx, --dag_regex]``                 ``airflow tasks clear [-R, --dag-regex]``
``airflow kerberos [-kt, --keytab]``                 ``airflow kerberos [-k, --keytab]``
``airflow webserver [-hn, --hostname]``              ``airflow webserver [-H, --hostname]``
``airflow worker [-cn, --celery_hostname]``          ``airflow celery worker [-H, --celery-hostname]``
``airflow flower [-hn, --hostname]``                 ``airflow celery flower [-H, --hostname]``
``airflow flower [-fc, --flower_conf]``              ``airflow celery flower [-c, --flower-conf]``
``airflow flower [-ba, --basic_auth]``               ``airflow celery flower [-A, --basic-auth]``
==================================================== ====================================================

For Airflow long option, use [kebab-case](https://en.wikipedia.org/wiki/Letter_case) instead of [snake_case](https://en.wikipedia.org/wiki/Snake_case)

================================== ===================================
Old option                         New option
================================== ===================================
``--task_regex``                   ``--task-regex``
``--start_date``                   ``--start-date``
``--end_date``                     ``--end-date``
``--dry_run``                      ``--dry-run``
``--no_backfill``                  ``--no-backfill``
``--mark_success``                 ``--mark-success``
``--donot_pickle``                 ``--donot-pickle``
``--ignore_dependencies``          ``--ignore-dependencies``
``--ignore_first_depends_on_past`` ``--ignore-first-depends-on-past``
``--delay_on_limit``               ``--delay-on-limit``
``--reset_dagruns``                ``--reset-dagruns``
``--rerun_failed_tasks``           ``--rerun-failed-tasks``
``--run_backwards``                ``--run-backwards``
``--only_failed``                  ``--only-failed``
``--only_running``                 ``--only-running``
``--exclude_subdags``              ``--exclude-subdags``
``--exclude_parentdag``            ``--exclude-parentdag``
``--dag_regex``                    ``--dag-regex``
``--run_id``                       ``--run-id``
``--exec_date``                    ``--exec-date``
``--ignore_all_dependencies``      ``--ignore-all-dependencies``
``--ignore_depends_on_past``       ``--ignore-depends-on-past``
``--ship_dag``                     ``--ship-dag``
``--job_id``                       ``--job-id``
``--cfg_path``                     ``--cfg-path``
``--ssl_cert``                     ``--ssl-cert``
``--ssl_key``                      ``--ssl-key``
``--worker_timeout``               ``--worker-timeout``
``--access_logfile``               ``--access-logfile``
``--error_logfile``                ``--error-logfile``
``--dag_id``                       ``--dag-id``
``--num_runs``                     ``--num-runs``
``--do_pickle``                    ``--do-pickle``
``--celery_hostname``              ``--celery-hostname``
``--broker_api``                   ``--broker-api``
``--flower_conf``                  ``--flower-conf``
``--url_prefix``                   ``--url-prefix``
``--basic_auth``                   ``--basic-auth``
``--task_params``                  ``--task-params``
``--post_mortem``                  ``--post-mortem``
``--conn_uri``                     ``--conn-uri``
``--conn_type``                    ``--conn-type``
``--conn_host``                    ``--conn-host``
``--conn_login``                   ``--conn-login``
``--conn_password``                ``--conn-password``
``--conn_schema``                  ``--conn-schema``
``--conn_port``                    ``--conn-port``
``--conn_extra``                   ``--conn-extra``
``--use_random_password``          ``--use-random-password``
``--skip_serve_logs``              ``--skip-serve-logs``
================================== ===================================


**Remove serve_logs command from CLI**

The ``serve_logs`` command has been deleted. This command should be run only by internal application mechanisms
and there is no need for it to be accessible from the CLI interface.

**dag_state CLI command**

If the DAGRun was triggered with conf key/values passed in, they will also be printed in the dag_state CLI response
ie. running, {"name": "bob"}
whereas in in prior releases it just printed the state:
ie. running

**Deprecating ignore_first_depends_on_past on backfill command and default it to True**

When doing backfill with ``depends_on_past`` dags, users will need to pass ``--ignore-first-depends-on-past``.
We should default it as ``true`` to avoid confusion


Changes to Airflow Plugins
^^^^^^^^^^^^^^^^^^^^^^^^^^

If you are using Airflow Plugins and were passing ``admin_views`` & ``menu_links`` which were used in the
non-RBAC UI (``flask-admin`` based UI), update it to use ``flask_appbuilder_views`` and ``flask_appbuilder_menu_links``.

**Old**:

.. code-block:: python

    from airflow.plugins_manager import AirflowPlugin

    from flask_admin import BaseView, expose
    from flask_admin.base import MenuLink


    class TestView(BaseView):
        @expose('/')
        def test(self):
            # in this example, put your test_plugin/test.html template at airflow/plugins/templates/test_plugin/test.html
            return self.render("test_plugin/test.html", content="Hello galaxy!")

    v = TestView(category="Test Plugin", name="Test View")

    ml = MenuLink(
        category='Test Plugin',
        name='Test Menu Link',
        url='https://airflow.apache.org/'
    )

    class AirflowTestPlugin(AirflowPlugin):
        admin_views = [v]
        menu_links = [ml]


**Change it to**:

.. code-block:: python

    from airflow.plugins_manager import AirflowPlugin
    from flask_appbuilder import expose, BaseView as AppBuilderBaseView

    class TestAppBuilderBaseView(AppBuilderBaseView):
        default_view = "test"

        @expose("/")
        def test(self):
            return self.render("test_plugin/test.html", content="Hello galaxy!")

    v_appbuilder_view = TestAppBuilderBaseView()
    v_appbuilder_package = {"name": "Test View",
                            "category": "Test Plugin",
                            "view": v_appbuilder_view}

    # Creating a flask appbuilder Menu Item
    appbuilder_mitem = {"name": "Google",
                        "category": "Search",
                        "category_icon": "fa-th",
                        "href": "https://www.google.com"}


    # Defining the plugin class
    class AirflowTestPlugin(AirflowPlugin):
        name = "test_plugin"
        appbuilder_views = [v_appbuilder_package]
        appbuilder_menu_items = [appbuilder_mitem]


Changes to extras names
^^^^^^^^^^^^^^^^^^^^^^^

The ``all`` extra were reduced to include only user-facing dependencies. This means
that this extra does not contain development dependencies. If you were using it and
depending on the development packages then you should use ``devel_all``.


Support for Airflow 1.10.x releases
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

As mentioned earlier in Step 2, the 1.10.14 release is intended to be a "bridge release"
which would be a step in the migration to Airflow 2.0.

After the Airflow 2.0 GA (General Availability) release, it expected that all
future Airflow development would be based on Airflow 2.0, including a series of
patch releases such as 2.0.1, 2.0.2 and then feature releases such as 2.1.

We plan to take a strict Semantic Versioning approach to our versioning and release process. This
means that we do not plan to make any backwards-incompatible changes in the 2.* releases. Any
breaking changes, including the removal of features deprecated in Airflow 2.0 will happen as part
of the Airflow 3.0 release.

The Airflow 1.10.x release tree will be supported for a limited time after the
GA release of Airflow 2.0 to give users time to upgrade from one of the Airflow 1.10.x releases.
Specifically, only "critical fixes" defined as fixes
to bugs that take down Production systems, will be backported to 1.10.x core for
six months after Airflow 2.0.0 is released.

In addition, Backport providers within
1.10.x, will be supported for critical fixes for three months after Airflow 2.0.0
is released.