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Code / API

Operators

Operators allow for generation of certain types of tasks that become nodes in the DAG when instantiated. All operators derive from BaseOperator and inherit many attributes and methods that way. Refer to the BaseOperator documentation for more details.

There are 3 main types of operators:

  • Operators that performs an action, or tell another system to perform an action
  • Transfer operators move data from one system to another
  • Sensors are a certain type of operator that will keep running until a certain criterion is met. Examples include a specific file landing in HDFS or S3, a partition appearing in Hive, or a specific time of the day. Sensors are derived from BaseSensorOperator and run a poke method at a specified poke_interval until it returns True.

BaseOperator

All operators are derived from BaseOperator and acquire much functionality through inheritance. Since this is the core of the engine, it's worth taking the time to understand the parameters of BaseOperator to understand the primitive features that can be leveraged in your DAGs.

.. autoclass:: airflow.models.BaseOperator

Operator API

.. automodule:: airflow.operators
    :show-inheritance:
    :members:
        BashOperator,
        BranchPythonOperator,
        DummyOperator,
        EmailOperator,
        ExternalTaskSensor,
        GenericTransfer,
        HdfsSensor,
        Hive2SambaOperator,
        HiveOperator,
        HivePartitionSensor,
        HiveToDruidTransfer,
        HiveToMySqlTransfer,
        SimpleHttpOperator,
        HttpSensor,
        MsSqlOperator,
        MsSqlToHiveTransfer,
        MySqlOperator,
        MySqlToHiveTransfer,
        PostgresOperator,
        PrestoCheckOperator,
        PrestoIntervalCheckOperator,
        PrestoValueCheckOperator,
        PythonOperator,
        S3KeySensor,
        S3ToHiveTransfer,
        SlackAPIOperator,
        SlackAPIPostOperator,
        SqlSensor,
        SubDagOperator,
        TimeSensor

Community Contributed Operators

.. automodule:: airflow.contrib.operators
    :show-inheritance:
    :members:
        VerticaOperator,
        VerticaToHiveTransfer

Macros

Here's a list of variables and macros that can be used in templates

Default Variables

The Airflow engine passes a few variables by default that are accessible in all templates

Variable Description
{{ ds }} the execution date as YYYY-MM-DD
{{ yesterday_ds }} yesterday's date as YYYY-MM-DD
{{ tomorrow_ds }} tomorrow's date as YYYY-MM-DD
{{ ds }} the execution date as YYYY-MM-DD
{{ execution_date }} the execution_date, (datateime.datetime)
{{ dag }} the DAG object
{{ task }} the Task object
{{ macros }} a reference to the macros package, described bellow
{{ task_instance }} the task_instance object
{{ ds_nodash }} the execution date as YYYYMMDD
{{ end_date }} same as {{ ds }}
{{ lastest_date }} same as {{ ds }}
{{ ti }} same as {{ task_instance }}
{{ params }} a reference to the user defined params dictionary
{{ task_instance_key_str }} a unique, human readable key to the task instance formatted {dag_id}_{task_id}_{ds}
conf the full configuration object located at airflow.configuration.conf which represents the content of your airflow.cfg

Note that you can access the object's attributes and methods with simple dot notation. Here are some examples of what is possible: {{ task.owner }}, {{ task.task_id }}, {{ ti.hostname }}, ... Refer to the models documentation for more information on the objects' attributes and methods.

Macros

These macros live under the macros namespace in your templates.

.. automodule:: airflow.macros
    :show-inheritance:
    :members:


.. automodule:: airflow.macros.hive
    :show-inheritance:
    :members:

Models

Models are built on top of th SQLAlchemy ORM Base class, and instances are persisted in the database.

.. automodule:: airflow.models
    :show-inheritance:
    :members: DAG, BaseOperator, TaskInstance, DagBag, Connection

Hooks

.. automodule:: airflow.hooks
    :show-inheritance:
    :members:
        HiveCliHook,
        HiveMetastoreHook,
        HiveServer2Hook,
        HttpHook,
        DruidHook,
        MsSqlHook,
        MySqlHook,
        PostgresHook,
        PrestoHook,
        S3Hook,
        SqliteHook

Community Contributed Hooks

.. automodule:: airflow.contrib.hooks
    :show-inheritance:
    :members:
        VerticaHook,
        FTPHook

Executors

Executors are the mechanism by which task instances get run.

.. automodule:: airflow.executors
    :show-inheritance:
    :members: LocalExecutor, CeleryExecutor, SequentialExecutor, MesosExecutor