ashb commented on a change in pull request #6348: [AIRFLOW-XXX] GSoD: Adding 'Create a custom operator' doc URL: https://github.com/apache/airflow/pull/6348#discussion_r336950814
########## File path: docs/howto/custom-operator.rst ########## @@ -0,0 +1,192 @@ + .. 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. + + +Creating a custom Operator +========================== + + +Airflow allows you to create new operators to suit the requirements of you or your team. +The extensibility is one of the many reasons which makes Apache Airflow powerful. + +You can create any operator you want by extending the :class:`airflow.models.baseoperator.BaseOperator` + +There are two methods that you need to override in a derived class: + +* Constructor - Define the parameters required for the operator. You only need to specify the arguments specific to your operator. + Use ``@apply_defaults`` decorator function to fill unspecified arguments with ``default_args``. You can specify the ``default_args`` + in the dag file. See :ref:`Default args <default-args>` for more details. + +* Execute - The code to execute when the runner calls the operator. The method contains the + airflow context as a parameter that can be used to read config values. + +Let's implement an example ``HelloOperator`` in a new file ``hello_operator.py``: + +.. code:: python + + from airflow.models.baseoperator import BaseOperator + from airflow.utils.decorators import apply_defaults + + class HelloOperator(BaseOperator): + + @apply_defaults + def __init__( + self, + name: str, + *args, **kwargs) -> None: + super().__init__(*args, **kwargs) + self.name = name + + def execute(self, context): + message = "Hello {}".format(name) + print(message) + return message + +You can now use the derived custom operator as follows: + +.. code:: python + + from custom_operator.hello_operator import HelloOperator + + with dag: + hello_task = HelloOperator(task_id='sample-task', name='foo_bar') + +**Note**: For imports to work, you should place the file in a directory that +is present in the ``PATH`` env. Airflow adds ``dags``, ``plugins``, and ``config`` directories Review comment: ```suggestion is present in the ``PATH`` env. Airflow adds ``dags/``, ``plugins/``, and ``config/`` directories ``` (I like this as a convention to make it clearer that these are directories we are talking about. I know we say it in words, but I find this makes it more "intuitave") ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
