chart/docs/production-guide.rst

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Production Guide
================

The following are things to consider when using this Helm chart in a production environment.

Database
--------

It is advised to set up an external database for the Airflow metastore. The default Helm chart deploys a
Postgres database running in a container. For **production** usage, a database running on a dedicated machine or
leveraging a cloud provider's database service such as AWS RDS, should be used. Embedded Postgres
lacks stability, monitoring and persistence features that you need for a production database. It is only there to
make it easier to test the Helm Chart in a "standalone" version, but you might experience data loss when you
are using it. Supported databases and versions can be found at :doc:`Set up a Database Backend <apache-airflow:howto/set-up-database>`.


.. note::

   When using the helm chart, you do not need to initialize the db with ``airflow db migrate``
   as outlined in :doc:`Set up a Database Backend <apache-airflow:howto/set-up-database>`.

To disable deployment of Postgres pod, set below values in your ``values.yaml`` file:

.. code-block:: yaml
   :caption: values.yaml

   postgresql:
     enabled: false

To provide the database credentials to Airflow, you have 2 options - in your values file or in a Kubernetes Secret.

Values file
^^^^^^^^^^^

This is the simpler options, as the chart will create a Kubernetes Secret for you. However, keep in mind your credentials will be in your values file.

.. code-block:: yaml
   :caption: values.yaml

   data:
     metadataConnection:
       user: <username>
       pass: <password>
       protocol: postgresql
       host: <hostname>
       port: 5432
       db: <database name>

.. warning::

   Due to security concerns, it is not advised to store Airflow database user credentials directly in the ``values.yaml`` file.

Kubernetes Secret
^^^^^^^^^^^^^^^^^

You can store the credentials in a Kubernetes Secret (it requires manual creation).

.. note::

   Any special character in the username/password must be URL encoded.

.. code-block:: bash

   kubectl create secret generic mydatabase --from-literal=connection=postgresql://user:pass@host:5432/db

After secret creation, configure the chart to use the secret:

.. code-block:: yaml
   :caption: values.yaml

   data:
     metadataSecretName: mydatabase

.. _production-guide:pgbouncer:

Metadata DB Cleanup
^^^^^^^^^^^^^^^^^^^

It is recommended to periodically clean up the Airflow metadata database to remove old records and keep the database size manageable.
A Kubernetes CronJob can be enabled for this purpose:

.. code-block:: yaml
   :caption: values.yaml

   databaseCleanup:
     enabled: true
     retentionDays: 90

For details regarding the ``airflow db clean`` command, see :ref:`db clean usage <cli-db-clean>` and for additional options which
can be configured via helm chart values, see :doc:`parameters reference <parameters-ref>`.

PgBouncer
---------

If you are using PostgreSQL as your database, you will likely want to enable `PgBouncer <https://www.pgbouncer.org/>`_ as well.
Due to distributed nature of Airflow, it can open a lot of database connections. Using a connection pooler can significantly
reduce the number of open connections on the database.

Database credentials stored Values file
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. code-block:: yaml
   :caption: values.yaml

   pgbouncer:
     enabled: true


Database credentials stored Kubernetes Secret
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The default connection string in this case will not work. You need to modify accordingly the Kubernetes secret:

.. code-block:: bash

   kubectl create secret generic mydatabase --from-literal=connection=postgresql://user:pass@pgbouncer_svc_name.deployment_namespace:6543/airflow-metadata

Furthermore, two additional Kubernetes Secret are required for PgBouncer to be able to properly work:

1. ``airflow-pgbouncer-stats`` secret:

   .. code-block:: bash

      kubectl create secret generic airflow-pgbouncer-stats --from-literal=connection=postgresql://user:pass@127.0.0.1:6543/pgbouncer?sslmode=disable

2. ``airflow-pgbouncer-config`` secret:

   .. code-block:: yaml
      :caption: airflow-pgbouncer-config

      apiVersion: v1
      kind: Secret
      metadata:
        name: airflow-pgbouncer-config
      data:
        pgbouncer.ini: dmFsdWUtMg0KDQo=
        users.txt: dmFsdWUtMg0KDQo=

   where:

   1. ``pgbouncer.ini`` value is equal to the base64 encoded version of below text:

      .. code-block:: text
         :caption: pgbouncer.ini

         [databases]
         airflow-metadata = host={external_database_host} dbname={external_database_dbname} port=5432 pool_size=10

         [pgbouncer]
         pool_mode = transaction
         listen_port = 6543
         listen_addr = *
         auth_type = scram-sha-256
         auth_file = /etc/pgbouncer/users.txt
         stats_users = postgres
         ignore_startup_parameters = extra_float_digits
         max_client_conn = 100
         verbose = 0
         log_disconnections = 0
         log_connections = 0

         server_tls_sslmode = prefer
         server_tls_ciphers = normal

   2. ``users.txt`` value is equal to the base64 encoded version of below text:

      .. code-block:: text
         :caption: users.txt

         "{ external_database_username }" "{ external_database_pass }"

In the ``values.yaml`` below secret-related parameters should be adjusted like:

.. code-block:: yaml
   :caption: values.yaml

   pgbouncer:
     enabled: true
     configSecretName: airflow-pgbouncer-config
     metricsExporterSidecar:
       statsSecretName: airflow-pgbouncer-stats

.. note::

   Depending on the size of your Airflow instance, you may want to adjust the following as well (defaults are shown):

   .. code-block:: yaml
      :caption: values.yaml

      pgbouncer:
        # The maximum number of connections to PgBouncer
        maxClientConn: 100
        # The maximum number of server connections to the metadata database from PgBouncer
        metadataPoolSize: 10
        # The maximum number of server connections to the result backend database from PgBouncer
        resultBackendPoolSize: 5

API Secret Key
--------------

You should set a static API secret key when deploying with Airflow chart as it will help ensure
your Airflow components only restart when necessary.

.. note::

   This section also applies to the webserver for Airflow 2 (simply replace ``api`` with ``webserver``).

.. warning::

   You should use a different secret key for every instance you run, as this key is used to sign
   session cookies and perform other security related functions.

Follow below steps to create static API secret key:

1. Generate a strong secret key:

   .. code-block:: bash

      python3 -c 'import secrets; print(secrets.token_hex(16))'

2. Add the secret to your values file:

   .. code-block:: yaml
      :caption: values.yaml

      apiSecretKey: <secret_key>

   or create a Kubernetes Secret and use ``apiSecretKeySecretName``:

   .. code-block:: yaml
      :caption: values.yaml

      apiSecretKeySecretName: my-api-secret
      # Where the random key is under `webserver-secret-key` in the k8s Secret

   .. warning::

      Due to security concerns, it is advised to use Kubernetes Secret instead of setting API secret key directly in the values file.

Example to create a Kubernetes Secret from ``kubectl``:

.. code-block:: bash

   kubectl create secret generic my-api-secret --from-literal="api-secret-key=$(python3 -c 'import secrets; print(secrets.token_hex(16))')"

The API secret key is also used to authorize requests to Celery workers when logs are retrieved. The token
generated using the secret key has a short expiry time though. Make sure that time on ALL the machines
that you run Airflow components on is synchronized (for example using ntpd). You might get
"forbidden" errors when the logs are accessed otherwise.

Eviction configuration
----------------------
When running Airflow along with the `Kubernetes Cluster Autoscaler <https://github.com/kubernetes/autoscaler>`_, it is important to configure whether pods can be safely evicted.
This setting can be configured in the Airflow chart at different levels:

.. code-block:: yaml
   :caption: values.yaml

   workers:
     safeToEvict: true
   scheduler:
     safeToEvict: true
   apiServer:
     safeToEvict: true

``workers.safeToEvict`` defaults to ``false``, and when using ``KubernetesExecutor``
``workers.safeToEvict`` shouldn't be set to ``true`` as the workers may be removed before finishing.

Extending and customizing Airflow Image
---------------------------------------

The Apache Airflow community, releases Docker Images which are ``reference images`` for Apache Airflow.
However, Airflow has more than 60 community managed providers (installable via extras) and some of the
default extras/providers installed are not used by everyone. Sometimes other extras/providers
are needed, sometimes (very often actually) you need to add your own custom dependencies,
packages or even custom providers, or add custom tools and binaries that are needed in
your deployment.

In Kubernetes and Docker terms, this means that you need another image with your specific requirements.
This is why you should learn how to build your own ``Docker`` (or more properly ``Container``) image.

Typical scenarios where you would like to use your custom image are adding:

* ``apt`` packages,
* ``PyPI`` packages,
* binary resources necessary for your deployment,
* custom tools needed in your deployment.

See :ref:`Extending Airflow Image <quick-start:extending-airflow-image>` and/or
`Building the image <https://airflow.apache.org/docs/docker-stack/build.html>`_ for more
details on how you can extend, customize and test the modifications of Airflow image.

Managing Dag Files
------------------

See :doc:`manage-dag-files`.

.. _production-guide:knownhosts:

knownHosts
^^^^^^^^^^

If you are using ``dags.gitSync.sshKeySecret``, you should also set ``dags.gitSync.knownHosts``. Here we will show the process
for GitHub, but the same can be done for any provider:

1. Grab GitHub's public key:

   .. code-block:: bash

      ssh-keyscan -t rsa github.com > github_public_key

2. Print the fingerprint for the public key:

   .. code-block:: bash

      ssh-keygen -lf github_public_key

3. Compare that output with `GitHub's SSH key fingerprints <https://docs.github.com/en/github/authenticating-to-github/githubs-ssh-key-fingerprints>`_.
4. If values are the same, add the public key to your values. It'll look something like this:

   .. code-block:: yaml
      :caption: values.yaml

      dags:
        gitSync:
          knownHosts: |
            github.com ssh-rsa AAAA...1/wsjk=

External Scheduler
------------------

To use an external Scheduler instance:

.. code-block:: yaml
   :caption: values.yaml

   scheduler:
     enabled: false

Ensure that your external scheduler is connected to the same redis host as workers.

Accessing the Airflow UI
------------------------

How you access the Airflow UI will depend on your environment; however, the chart does support various options.

External API Server
^^^^^^^^^^^^^^^^^^^

To use an external API Server:

.. code-block:: yaml
   :caption: values.yaml

   apiServer:
     enabled: false

Ingress
^^^^^^^

You can create and configure ``Ingress`` objects. See the :ref:`Ingress chart parameters <parameters:ingress>`.
For more information on ``Ingress``, see the
`Kubernetes Ingress documentation <https://kubernetes.io/docs/concepts/services-networking/ingress/>`_.

LoadBalancer Service
^^^^^^^^^^^^^^^^^^^^

You can change the Service type for the API Server to be ``LoadBalancer``, and set any necessary annotations:

.. code-block:: yaml
   :caption: values.yaml

   apiServer:
     service:
       type: LoadBalancer

For more information on ``LoadBalancer`` Services, see the `Kubernetes LoadBalancer Service Documentation
<https://kubernetes.io/docs/concepts/services-networking/service/#loadbalancer>`_.

Logging
-------

Depending on your choice of executor, task logs may not work out of the box. All logging choices can be found
at :doc:`manage-logs`.

Metrics
-------

The chart supports sending metrics to an existing StatsD instance or provide a Prometheus endpoint.

Prometheus Endpoint
^^^^^^^^^^^^^^^^^^^

The metrics endpoint is available at ``svc/{{ .Release.Name }}-statsd:9102/metrics``.

External StatsD
^^^^^^^^^^^^^^^

To use an external StatsD instance:

.. code-block:: yaml
   :caption: values.yaml

   statsd:
     enabled: false
   config:
     metrics:
       statsd_on: true
       statsd_host: ...
       statsd_port: ...

IPv6 StatsD
^^^^^^^^^^^

To use an StatsD instance with IPv6 address. Example with Kubernetes with IPv6 enabled:

.. code-block:: yaml
   :caption: values.yaml

   statsd:
     enabled: true
   config:
     metrics:
       statsd_on: 'True'
       statsd_host: ...
       statsd_ipv6: 'True'
       statsd_port: ...
       statsd_prefix: airflow

Datadog
^^^^^^^
If you are using a Datadog agent in your environment, this will enable Airflow to export metrics to the Datadog agent.

.. code-block:: yaml
   :caption: values.yaml

   statsd:
     enabled: false
   config:
     metrics:
       statsd_on: true
       statsd_port: 8125
   extraEnv: |-
     - name: AIRFLOW__METRICS__STATSD_HOST
       valueFrom:
         fieldRef:
           fieldPath: status.hostIP

Celery Backend
--------------

If you are using ``CeleryExecutor`` or ``CeleryKubernetesExecutor``, you can bring your own Celery backend.

By default, the chart will deploy Redis. However, you can use any supported Celery backend instead:

.. code-block:: yaml
   :caption: values.yaml

   redis:
     enabled: false
   data:
     brokerUrl: redis://redis-user:password@redis-host:6379/0

For more information about setting up a Celery broker, refer to the
exhaustive `Celery documentation on the topic <http://docs.celeryproject.org/en/latest/getting-started/>`_.

Security Context
----------------

Constraints
^^^^^^^^^^^

A ``Security Context Constraint`` (SCC) is a OpenShift construct that works as a RBAC rule. However, it targets Pods instead of users.
When defining a SCC, one can control actions and resources a POD can perform or access during startup and runtime.

The SCCs are split into different levels or categories with the ``restricted`` SCC being the default one assigned to Pods.
When deploying Airflow to OpenShift, one can leverage the SCCs and allow the Pods to start containers utilizing the ``anyuid`` SCC.

In order to enable the usage of SCCs, one must set the parameter ``rbac.createSCCRoleBinding`` to ``true`` as shown below:

.. code-block:: yaml
   :caption: values.yaml

   rbac:
     create: true
     createSCCRoleBinding: true

In this chart, SCCs are bound to the Pods via RoleBindings meaning that the option ``rbac.create`` must also be set to ``true`` in order to fully enable the SCC usage.

For more information about SCCs and what can be achieved with this construct, please refer to `Managing security context constraints <https://docs.openshift.com/container-platform/latest/authentication/managing-security-context-constraints.html#scc-prioritization_configuring-internal-oauth/>`_.

Configuration
^^^^^^^^^^^^^

In Kubernetes a ``securityContext`` can be used to define user ids, group ids and capabilities such as running a container in privileged mode.

When deploying an application to Kubernetes, it is recommended to give the least privilege to containers
to reduce access and protect the host where the container is running.

In the Airflow Helm chart, the ``securityContext`` can be configured in several ways:

* :ref:`uid <parameters:Airflow>` - configures the global uid or RunAsUser
* :ref:`gid <parameters:Airflow>` - configures the global gid or fsGroup
* :ref:`securityContexts <parameters:Kubernetes>` - same as ``uid``, but allows for setting all `Pod securityContext options <https://kubernetes.io/docs/reference/generated/kubernetes-api/latest/#podsecuritycontext-v1-core>`_ and `Container securityContext options <https://kubernetes.io/docs/reference/generated/kubernetes-api/latest/#securitycontext-v1-core>`_

The same way one can configure the global :ref:`securityContexts <parameters:Kubernetes>`. It is also possible to configure different values for specific workloads by setting their local ``securityContexts`` as follows:

.. code-block:: yaml
   :caption: values.yaml

   scheduler:
     securityContexts:
       pod:
         runAsUser: 5000
         fsGroup: 0
       containers:
         allowPrivilegeEscalation: false


In the example above, the scheduler pod ``securityContext`` will be set to ``runAsUser: 5000`` and ``fsGroup: 0``.  The scheduler container ``securityContext`` will be set to ``allowPrivilegeEscalation: false``.

As one can see, the local setting will take precedence over the global setting when defined. The following explains the precedence rule for ``securityContexts`` options in this chart:

.. code-block:: yaml
   :caption: values.yaml

   uid: 40000
   gid: 0

   securityContexts:
     pod:
       runAsUser: 50000
       fsGroup: 0

   scheduler:
     securityContexts:
       pod:
         runAsUser: 1001
         fsGroup: 0

This will generate the following scheduler deployment:

.. code-block:: yaml
   :caption: airflow-scheduler

   kind: Deployment
   apiVersion: apps/v1
   metadata:
     name: airflow-scheduler
   spec:
     template:
       spec:
         securityContext:    # As the securityContexts was defined in ``scheduler``, its value will take priority
           runAsUser: 1001
           fsGroup: 0

If we remove both the ``securityContexts`` and ``scheduler.securityContexts`` from the example above:

.. code-block:: yaml
   :caption: values.yaml

   uid: 40000
   gid: 0

   securityContexts: {}

   scheduler:
     securityContexts: {}

it will generate the following scheduler deployment:

.. code-block:: yaml
   :caption: airflow-scheduler

   kind: Deployment
   apiVersion: apps/v1
   metadata:
     name: airflow-scheduler
   spec:
     template:
       spec:
         securityContext:
           runAsUser: 40000   # As the securityContext was not defined in ``scheduler`` or ``podSecurity``, the value from uid will be used
           fsGroup: 0         # As the securityContext was not defined in ``scheduler`` or ``podSecurity``, the value from gid will be used
         initContainers:
           - name: wait-for-airflow-migrations
         ...
         containers:
           - name: scheduler
         ...

And finally if we set ``securityContexts``, but not ``scheduler.securityContexts``:

.. code-block:: yaml
   :caption: values.yaml

   uid: 40000
   gid: 0

   securityContexts:
     pod:
       runAsUser: 50000
       fsGroup: 0

   scheduler:
     securityContexts: {}

This will generate the following scheduler deployment:

.. code-block:: yaml
   :caption: airflow-scheduler

   kind: Deployment
   apiVersion: apps/v1
   metadata:
     name: airflow-scheduler
   spec:
     template:
       spec:
         securityContext:     # As the securityContexts was not defined in ``scheduler``, the values from securityContexts will take priority
           runAsUser: 50000
           fsGroup: 0
         initContainers:
           - name: wait-for-airflow-migrations
         ...
         containers:
           - name: scheduler
         ...

Built-in secrets and environment variables
------------------------------------------

The Helm Chart by default uses Kubernetes Secrets to store secrets that are needed by Airflow.
The contents of those secrets are by default turned into environment variables that are read by
Airflow.

.. note::

   Some of the environment variables have several variants to support older versions of Airflow.

By default, the secret names are determined from the Release Name used when the Helm Chart,
but you can also use a different secret to set the variables or disable using secrets
entirely and rely on environment variables (specifically if you want to use ``_CMD`` or ``__SECRET`` variant
of the environment variable).

However, Airflow supports other variants of setting secret configuration. You can specify a system
command to retrieve and automatically rotate the secret (by defining variable with ``_CMD`` suffix) or
to retrieve a variable from secret backed (by defining the variable with ``_SECRET`` suffix).

If the ``<VARIABLE_NAME>`` is set, it takes precedence over the ``_CMD`` and ``_SECRET`` variant, so
if you want to set one of the ``_CMD`` or ``_SECRET`` variants, you **must** disable the built in
variables retrieved from Kubernetes secrets, by setting ``.Values.enableBuiltInSecretEnvVars.<VARIABLE_NAME>``
to ``false``.

For example in order to use a command to retrieve the DB connection, you should (in your ``values.yaml``
file) specify:

.. code-block:: yaml
   :caption: values.yaml

   extraEnv:
     AIRFLOW_CONN_AIRFLOW_DB_CMD: "/usr/local/bin/retrieve_connection_url"
   enableBuiltInSecretEnvVars:
     AIRFLOW_CONN_AIRFLOW_DB: false

Here is the full list of secrets that can be disabled and replaced by ``_CMD`` and ``_SECRET`` variants:

+-------------------------------------------------------+------------------------------------------+--------------------------------------------------+
| Default secret name if secret name not specified      | Use a different Kubernetes Secret        | Airflow Environment Variable                     |
+=======================================================+==========================================+==================================================+
| ``<RELEASE_NAME>-airflow-metadata``                   | ``.Values.data.metadataSecretName``      | | ``AIRFLOW_CONN_AIRFLOW_DB``                    |
|                                                       |                                          | | ``AIRFLOW__DATABASE__SQL_ALCHEMY_CONN``        |
+-------------------------------------------------------+------------------------------------------+--------------------------------------------------+
| ``<RELEASE_NAME>-fernet-key``                         | ``.Values.fernetKeySecretName``          | ``AIRFLOW__CORE__FERNET_KEY``                    |
+-------------------------------------------------------+------------------------------------------+--------------------------------------------------+
| ``<RELEASE_NAME>-api-secret-key``                     | ``.Values.apiSecretKeySecretName``       | ``AIRFLOW__API__SECRET_KEY``                     |
+-------------------------------------------------------+------------------------------------------+--------------------------------------------------+
| ``<RELEASE_NAME>-jwt-secret``                         | ``.Values.jwtSecretName``                | ``AIRFLOW__API_AUTH__JWT_SECRET``                |
+-------------------------------------------------------+------------------------------------------+--------------------------------------------------+
| ``<RELEASE_NAME>-webserver-secret-key``               | ``.Values.webserverSecretKeySecretName`` | ``AIRFLOW__WEBSERVER__SECRET_KEY``               |
+-------------------------------------------------------+------------------------------------------+--------------------------------------------------+
| ``<RELEASE_NAME>-airflow-result-backend``             | ``.Values.data.resultBackendSecretName`` | ``AIRFLOW__CELERY__RESULT_BACKEND``              |
+-------------------------------------------------------+------------------------------------------+--------------------------------------------------+
| ``<RELEASE_NAME>-airflow-broker-url``                 | ``.Values.data.brokerUrlSecretName``     | ``AIRFLOW__CELERY__BROKER_URL``                  |
+-------------------------------------------------------+------------------------------------------+--------------------------------------------------+
| ``<RELEASE_NAME>-elasticsearch``                      | ``.Values.elasticsearch.secretName``     | ``AIRFLOW__ELASTICSEARCH__HOST``                 |
+-------------------------------------------------------+------------------------------------------+--------------------------------------------------+

There are also a number of secrets, which names are also determined from the release name, that do not need to
be disabled. This is because either they do not follow the ``_CMD`` or ``_SECRET`` pattern, are variables
which do not start with ``AIRFLOW__``, or they do not have a corresponding variable.

There is also ``AIRFLOW__CELERY__FLOWER_BASIC_AUTH``, that does not need to be disabled,
even if you want set the ``_CMD`` and ``_SECRET`` variant. This variable is not set by default. It is only set
when ``.Values.flower.secretName`` is set or when ``.Values.flower.user`` and ``.Values.flower.password``
are set. If you do not set any of the ``.Values.flower.*`` variables, you can freely configure
flower Basic Auth using the ``_CMD`` or ``_SECRET`` variant without disabling the basic variant.

+-------------------------------------------------------+------------------------------------------+------------------------------------------------+
| Default secret name if secret name not specified      | Use a different Kubernetes Secret        | Airflow Environment Variable                   |
+=======================================================+==========================================+================================================+
| ``<RELEASE_NAME>-redis-password``                     | ``.Values.redis.passwordSecretName``     | ``REDIS_PASSWORD``                             |
+-------------------------------------------------------+------------------------------------------+------------------------------------------------+
| ``<RELEASE_NAME>-pgbouncer-config``                   | ``.Values.pgbouncer.configSecretName``   |                                                |
+-------------------------------------------------------+------------------------------------------+------------------------------------------------+
| ``<RELEASE_NAME>-pgbouncer-certificates``             |                                          |                                                |
+-------------------------------------------------------+------------------------------------------+------------------------------------------------+
| ``<RELEASE_NAME>-kerberos-keytab``                    |                                          |                                                |
+-------------------------------------------------------+------------------------------------------+------------------------------------------------+
| ``<RELEASE_NAME>-flower``                             | ``.Values.flower.secretName``            | ``AIRFLOW__CELERY__FLOWER_BASIC_AUTH``         |
+-------------------------------------------------------+------------------------------------------+------------------------------------------------+

A secret named ``<RELEASE_NAME>-registry`` is also created when ``.Values.registry.connection`` is
defined and neither ``.Values.registry.secretName`` nor ``.Values.imagePullSecrets`` is set. However,
this behavior is deprecated in favor of explicitly defining ``.Values.imagePullSecrets``.

You can read more about advanced ways of setting configuration variables in the
:doc:`apache-airflow:howto/set-config`.

Service Account Token Volume Configuration
------------------------------------------

When using pod-launching executors (``CeleryExecutor``, ``CeleryKubernetesExecutor``, ``KubernetesExecutor``, ``LocalKubernetesExecutor``),
you can configure how Kubernetes service account tokens are mounted into pods. This provides enhanced security control
and compatibility with security policies like Kyverno.

Background
^^^^^^^^^^

By default, Kubernetes automatically mounts service account tokens into pods via the ``automountServiceAccountToken`` setting.
However, for security reasons, you might want to disable automatic mounting and manually configure service account token volumes instead.

This feature addresses Bug `#59099 <https://github.com/apache/airflow/issues/59099>`_ where ``scheduler.serviceAccount.automountServiceAccountToken: false`` was ignored
when using the KubernetesExecutor. The solution implements a defense-in-depth approach with both ServiceAccount-level
and Pod-level controls.

Container-Specific Security
^^^^^^^^^^^^^^^^^^^^^^^^^^^

The Service Account Token Volume is mounted **only** in containers that require Kubernetes API access, implementing the
**Principle of Least Privilege**:

* **Scheduler Container**: Receives Service Account Token as it needs API access for pod management
* **Init Container "wait-for-airflow-migrations"**: No Service Account Token as it only performs database migrations
* **Sidecar Container "scheduler-log-groomer"**: No Service Account Token as it only performs log cleanup operations

This container-specific approach ensures that:

* **Database Migration Container**: Only accesses the database for schema updates as no Kubernetes API access required
* **Log Groomer Container**: Only performs filesystem operations for log cleanup as no API access required
* **Scheduler Container**: Requires API access for launching and managing pods with pod-launching executors

**Security Benefits:**

* **Explicit control**: Manual configuration makes token mounting intentional and visible
* **Policy compliance**: Compatible with security policies that restrict ``automountServiceAccountToken: true``
* **Defense-in-depth**: Provides both ServiceAccount-level and Pod-level security controls
* **Custom expiration**: Allows setting shorter token lifetimes for enhanced security
* **Container isolation**: Only scheduler container receives API access, reducing attack surface
* **Principle of Least Privilege**: Each container receives only the minimum required permissions

Configuration Options
^^^^^^^^^^^^^^^^^^^^^

The service account token volume configuration is available for the scheduler component and includes the following options:

.. code-block:: yaml
   :caption: values.yaml

   scheduler:
     serviceAccount:
       automountServiceAccountToken: false
       serviceAccountTokenVolume:
         enabled: true
         mountPath: /var/run/secrets/kubernetes.io/serviceaccount
         volumeName: kube-api-access
         expirationSeconds: 3600
         audience: ~

Security Implications
^^^^^^^^^^^^^^^^^^^^^

Manual token volumes should be used when:

* Security policies require explicit control over service account token mounting
* Using security policy engines like Kyverno that restrict automatic token mounting
* Implementing defense-in-depth security strategies
* You need custom token expiration times or audiences
* Compliance frameworks mandate container-specific privilege assignment

Use Cases and Examples
^^^^^^^^^^^^^^^^^^^^^^

For comprehensive configuration examples, security scenarios, and detailed use cases,
see :doc:`service-account-token-examples`.

Supported Executors
^^^^^^^^^^^^^^^^^^^

The service account token volume configuration is only effective for pod-launching executors:

* ``CeleryExecutor`` - when launching Celery worker pods
* ``CeleryKubernetesExecutor`` - for both Celery workers and Kubernetes task pods
* ``KubernetesExecutor`` - when launching task pods in Kubernetes
* ``LocalKubernetesExecutor`` - for Kubernetes task pods in local mode

For other executors (``LocalExecutor``, ``SequentialExecutor``), this configuration has no effect
as they don't launch additional pods.

Migration from Automatic to Manual Token Mounting
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

To migrate from automatic to manual token mounting:

1. Test the configuration in a non-production environment first
2. Update your ``values.yaml``:

   .. code-block:: yaml
      :caption: values.yaml

      scheduler:
        serviceAccount:
          automountServiceAccountToken: false
          serviceAccountTokenVolume:
            enabled: true

3. Deploy the changes using Helm upgrade
4. Verify that the scheduler can still launch pods successfully
5. Monitor for any authentication issues in the logs

Troubleshooting
^^^^^^^^^^^^^^^

**Common Issues:**

* **Authentication failures**: Ensure ``serviceAccountTokenVolume.enabled`` is set to ``true`` when ``automountServiceAccountToken`` is ``false``
* **Permission denied**: Verify that the service account has the necessary RBAC permissions
* **Token expiration**: Check if ``expirationSeconds`` is too short for your workload patterns

**Debugging:**

Check the scheduler logs for authentication-related errors:

.. code-block:: bash

   kubectl logs deployment/airflow-scheduler -n <namespace>

Verify the projected volume is mounted correctly:

.. code-block:: bash

   kubectl describe pod <scheduler-pod-name> -n <namespace>

Backward Compatibility
^^^^^^^^^^^^^^^^^^^^^^

This feature maintains full backward compatibility:

* Existing deployments with ``automountServiceAccountToken: true`` continue to work unchanged
* The ``serviceAccountTokenVolume`` configuration is only applied when explicitly enabled
* Default values ensure no breaking changes for existing installations

For more information about Kubernetes service account tokens and projected volumes, see the
`Kubernetes documentation on service account tokens <https://kubernetes.io/docs/tasks/configure-pod-container/configure-service-account/#serviceaccount-token-volume-projection>`_.