Airflow plugins

Plugins are external features that can be added to customize your Airflow installation. They are automatically imported upon starting your Airflow instance if they have been added to plugins folder of an Airflow project.

In this guide, you'll learn how to add a plugin to your Airflow instance and what Airflow components can be part of a plugin.

Assumed knowledge​

To get the most out of this guide, you should have an understanding of:

• Basic Airflow concepts. See Introduction to Apache Airflow.
• Airflow core components. See Airflow's components.
• The basics of Flask. See the Flask documentation.

When to use plugins​

Plugins offer a flexible way to customize your Airflow experience by building on top of existing Airflow components. For example, you can:

• Add views to your Airflow UI that display contents of the Airflow metadata database in a custom way.
• Build an application that monitors Airflow's functioning and sends out custom alerts, for example in case of a certain number of DAGs failing in a specified time frame.
• Add a button to the task instance Details view that dynamically links to files or logs in external data tools relevant to the task.

How to create a plugin​

To add a new plugin to your Airflow instance, you need to create a Python file in the plugins folder of your Airflow project. Within that file, create a class which inherits from the AirflowPlugin to define the plugin. The code snippet below defines a plugin with the name empty without any components.

from airflow.plugins_manager import AirflowPlugin


class MyAirflowPlugin(AirflowPlugin):
    # name your plugin, this is mandatory
    name = "empty"

    ## Add plugin components
    # ...
    # ...
    # ...

    # Add an optional callback to perform actions when airflow starts and
    # the plugin is loaded.
    # NOTE: Ensure your plugin has *args, and **kwargs in the method definition
    #   to protect against extra parameters injected into the on_load()
    #   function in future changes
    def on_load(*args, **kwargs):
        # perform Plugin boot actions
        pass

The list of currently active plugins can be viewed in the Airflow UI under Admin -> Plugins. The code above creates the following entry:

Plugin components​

Functionality is added to a plugin by adding components to the class which defines the plugin. There are 10 types of plugin components that can be added to Airflow. In this guide we will show the more commonly used components, including:

• appbuilder_menu_items allow you to add additional sections and links to the Airflow menu.
• flask_blueprints and appbuilder_views offer the possibility to build a Flask project on top of Airflow.
• operator_extra_links and global_operator_extra_links are ways to add links to Airflow task instances.
• macros expand upon existing Jinja templates using custom functions.
• listeners define custom code to execute whenever certain events happen anywhere in your Airflow instance.

Other types of plugin components not covered in this guide include:

• timetables offer the option to register custom timetables that define schedules which cannot be expressed in CRON. See the DAG Schedule DAGs in Airflow guide for more information and a code example.
• executors add the possibility to use a custom executor in your Airflow instance.

Appbuilder menu items​

You can update the menu at the top of the Airflow UI to contain custom tabs with links to external websites. Adding top-level menu items and adding sub-items are both supported.

If you are an Astro user, in order for the menu items to be visible to all users, the top-level menu item must be set to "Custom Menu" or one of the existing top-level menus such as "Docs" in the example below. This is done by passing the appropriate top-level menu to the category and name parameters in the menu sub-item.

The following code creates a plugin that adds two menu items.

• apache_mitem_subitem is a sub-item which is added to Custom Menu. It is labeled Apache and links to the Apache homepage.
• cosmos_mitem_subitem is a sub-item which is added to the Docs menu. It is labeled Cosmos Docs and links out to the documentation for Cosmos.

Both additional menu items are added to the app_builder_menu_items component of a plugin called Menu items plugin which is defined in the MyMenuItemsPlugin class.

from airflow.plugins_manager import AirflowPlugin

# creating a new sub-item in the Custom Menu item
apache_mitem_subitem = {
    "label": "Apache",
    "href": "https://www.apache.org/",
    "category": "Custom Menu",
    "name": "Custom Menu",
}

# creating a new sub-item in the Docs menu item
cosmos_mitem_subitem = {
    "label": "Cosmos Docs",
    "href": "https://astronomer.github.io/astronomer-cosmos/",
    "category": "Docs",
    "name": "Docs",
}

# defining the plugin class
class MyMenuItemsPlugin(AirflowPlugin):
    name = "Menu items plugin"

    # adding the menu items to the plugin
    appbuilder_menu_items = [apache_mitem_subitem, cosmos_mitem_subitem]

The screenshots below show the additional menu items in the Airflow UI.

If you are not using Astro, you can create a top-level menu item with any name. For example, you can directly create a top-level menu item named "Apache" that links to the Apache homepage with the below code.

from airflow.plugins_manager import AirflowPlugin

# creating the Apache top-level menu item
apache_mitem_toplevel = {
    "name": "Apache",
    "href": "https://www.apache.org/",
}

# defining the plugin class
class MyMenuItemsPlugin(AirflowPlugin):
    name = "Menu items plugin"

    # adding the menu item to the plugin
    appbuilder_menu_items = [apache_mitem_toplevel]

The screenshot below shows the top-level Apache menu item.

Flask Blueprints and Appbuilder views​

Flask blueprints and views are plugin components that allow you to add more elaborate customization to the Airflow UI. A Flask blueprint functions as an organizational tool to group related views and supporting code while Flask views render webpages from html templates.

You can add a view to render a simple templated HTML file on top of the Airflow UI by following the steps below. The code also includes an additional example of creating an Appbuilder menu item (similar to the Cosmos Docs example) that can be accessed from the same top-level "Custom Menu" as the Appbuilder view.

1. Create a folder within the plugins directory called templates.

2. Within that folder create a HTML file called test.html and copy the following code into it:

   {% extends "appbuilder/base.html" %}
   {% block content %}
       <p>Airflow is {{ content }}!</p>
   {% endblock %}
   

3. In the plugins directory, add a Python file called my_first_view_plugin.py. Copy the code below. If you are using Astro, different code is required depending on whether your Airflow version is < 2.10 or >= 2.10.

from airflow.plugins_manager import AirflowPlugin
from flask import Blueprint
from flask_appbuilder import expose, BaseView as AppBuilderBaseView
from airflow.configuration import conf

# from airflow.www.auth import has_access  # uncomment to use the plugin on Astro
# from airflow.security import permissions  # uncomment to use the plugin on Astro

CUSTOM_ASTRO_RESOURCE = "Custom Menu"

# define a Flask blueprint
my_blueprint = Blueprint(
    "test_plugin",
    __name__,
    # register airflow/plugins/templates as a Jinja template folder
    template_folder="templates",
)


# create a flask appbuilder BaseView
class MyBaseView(AppBuilderBaseView):
    default_view = "test"

    # If you are using Astro, uncomment the "has_access" line below, and do not change it
    @expose("/")
    # @has_access([(permissions.ACTION_CAN_ACCESS_MENU, CUSTOM_ASTRO_RESOURCE)])
    def test(self):
        # render the HTML file from the templates directory with content
        return self.render_template("test.html", content="awesome")


# instantiate MyBaseView
my_view = MyBaseView()

my_view_package = {
    "category": CUSTOM_ASTRO_RESOURCE,
    "name": CUSTOM_ASTRO_RESOURCE,
    "view": my_view,
    "label": "Custom Plugins",
}

# Appbuilder menu item without Flask view
google_mitem = {
    "category": CUSTOM_ASTRO_RESOURCE,
    "label": "Google",
    "href": "https://www.google.com",
    "name": CUSTOM_ASTRO_RESOURCE,
}


# define the plugin class
class MyViewPlugin(AirflowPlugin):
    # name the plugin
    name = "My appbuilder view"
    # add the blueprint and appbuilder components
    flask_blueprints = [my_blueprint]
    appbuilder_views = [my_view_package]
    appbuilder_menu_items = [google_mitem]

from airflow.plugins_manager import AirflowPlugin
from flask import Blueprint
from flask_appbuilder import expose, BaseView as AppBuilderBaseView
from airflow.configuration import conf

# from airflow.www.auth import has_access  # uncomment to use the plugin on Astro
# from airflow.security import permissions  # uncomment to use the plugin on Astro

CUSTOM_ASTRO_RESOURCE = "Custom Menu"

# define a Flask blueprint
my_blueprint = Blueprint(
    "test_plugin",
    __name__,
    # register airflow/plugins/templates as a Jinja template folder
    template_folder="templates",
)


# create a flask appbuilder BaseView
class MyBaseView(AppBuilderBaseView):
    default_view = "test"

    # If you are using Astro, uncomment the "has_access" line below, and do not change it
    @expose("/")
    # @has_access([(permissions.ACTION_CAN_ACCESS_MENU, CUSTOM_ASTRO_RESOURCE)])
    def test(self):
        # render the HTML file from the templates directory with content
        return self.render_template("test.html", content="awesome")


# instantiate MyBaseView
my_view = MyBaseView()

# get the base URL of the Airflow webserver
base_url = conf.get("webserver", "base_url")
view_link = f"{str(base_url)}/{my_view.__class__.__name__.lower()}"

# Note: The view below is without "name" due to a bug that doesn't propagate labels in Airflow < 2.10
my_view_package = {
    "category": CUSTOM_ASTRO_RESOURCE,
    "view": my_view,
}

# "my_mitem" below uses the "view_link" to make it reachable via a clickable link in Airflow < 2.10
my_mitem = {
    "label": "Custom Plugins",
    "href": view_link,
    "name": CUSTOM_ASTRO_RESOURCE,
    "category": CUSTOM_ASTRO_RESOURCE,
}

# Appbuilder menu item without Flask view
google_mitem = {
    "category": CUSTOM_ASTRO_RESOURCE,
    "label": "Google",
    "href": "https://www.google.com",
    "name": CUSTOM_ASTRO_RESOURCE,
}


# define the plugin class
class MyViewPlugin(AirflowPlugin):
    # name the plugin
    name = "My appbuilder view"
    # add the blueprint and appbuilder_views components
    flask_blueprints = [my_blueprint]
    appbuilder_views = [my_view_package]
    appbuilder_menu_items = [my_mitem, google_mitem]

4. Start your Airflow instance using astro dev start or astro dev restart if you were already running Airflow.

This plugin will add a top-level menu item called Custom Menu which contains the sub-items Custom Plugins and Google.

By clicking on Custom Plugins you can access the Flask View that was defined as my_view. It shows the HTML template (test.html) rendered with the provided content.

Clicking on Google will take you to the url https://www.google.com similar to the Cosmos Docs example in the previous Appbuilder menu items section.

from airflow.www.auth import has_access
from airflow.security import permissions 

# ...

CUSTOM_ASTRO_RESOURCE = "Custom Menu"

# ...

# create a flask appbuilder BaseView
class MyBaseView(AppBuilderBaseView):
    default_view = "test"

    # Do not change the "has_access" line below
    @expose("/")
    @has_access([(permissions.ACTION_CAN_ACCESS_MENU, CUSTOM_ASTRO_RESOURCE)])
    def test(self):
        # render the HTML file from the templates directory with content
        return self.render_template("test.html", content="awesome")

CUSTOM_ASTRO_RESOURCE = "Custom Menu"

# ...

# Menu sub-item
google_mitem = {
   "category": CUSTOM_ASTRO_RESOURCE,
   "label": "Google",
   "href": "https://www.google.com",
   "name": CUSTOM_ASTRO_RESOURCE,
   }

my_view_package = {
    "category": CUSTOM_ASTRO_RESOURCE,
    "view": my_view,
}

from airflow.configuration import conf

 # ...

base_url = conf.get("webserver", "base_url")
view_link = f"{str(base_url)}/{my_view.__class__.__name__.lower()}"

   my_mitem = {
    "label": "Custom Plugins",
    "href": view_link,
    "name": CUSTOM_ASTRO_RESOURCE,
    "category": CUSTOM_ASTRO_RESOURCE,
}

Operator extra links​

Operator extra links are additional buttons with links that can be added to specific operators. They can be defined as Python classes derived from the BaseOperatorLink class. The example below shows how to create a new operator extra link MyLink that is applied to MyOperator1 and MyOperator2. The operator extra link is registered with the MyAirflowPlugin by adding it its operator_extra_links list.

from airflow.models.baseoperator import BaseOperatorLink
from include.custom_operators import MyOperator1, MyOperator2
from airflow.plugins_manager import AirflowPlugin

# create the operator extra link
class MyLink(BaseOperatorLink):

    # name the link button
    name = "My extra link"

    # add the link button to one or more operators
    operators = [MyOperator1, MyOperator2]

    # function determining the link
    def get_link(self, operator, *, ti_key=None):
        return "http://my_link.com/"


# add the operator extra link to a plugin
class MyOperatorExtraLink(AirflowPlugin):
    name = "my_plugin_name"
    operator_extra_links = [
        MyLink(),
    ]

The screenshot below shows an operator extra link called "HTTP cat" that was added to the custom CatHttpOperator. For more instructions, see this step-by-step tutorial on how to add operator extra links.

Global operator extra links​

Global operator extra links are additional buttons with links that will be added to every operator. This example adds a button named Airflow docs to all operators that links out to the Airflow documentation.

class GlobalLink(BaseOperatorLink):
    # name the link button
    name = "Airflow docs"

    # function determining the link
    def get_link(self, operator, *, ti_key=None):
        return "https://airflow.apache.org/"


# add the operator extra link to a plugin
class MyGlobalLink(AirflowPlugin):
    name = "my_plugin_name"
    global_operator_extra_links = [
        GlobalLink(),
    ]

You can access the button on task instances in both the Graph and Grid views.

Macros​

In Airflow you can define custom macros which can be accessed using Jinja templating. Macros can be added at the DAG level by defining them in the DAG parameter user_defined_macros as shown in Using Airflow templates. If you want to make macros available to your whole Airflow instance you can register them as a plugin.

Common use cases for custom macros include:

• Injecting dynamic datetime objects into DAG code in formats not available in pre-defined macros. For example, converting the {{ ts }} predefined macro, which provides the logical date of the DAG as a timestamp from YYYY-MM-DDThh:mm:ss+00:00 to hh:mm.
• Injecting dynamic arguments into DAG code based on Python logic. For example, passing a different argument to a function on weekdays versus the weekend.
• Injecting dynamic arguments into DAG code based on XCom values. For example, using a different target blob storage depending on how many files will be ingested, a count determined and pushed to XCom by an upstream task.

from airflow.plugins_manager import AirflowPlugin
from random import randint


def random_number_macro():
    return randint(0, 1000)


class MyAirflowMacro(AirflowPlugin):
    name = "my_macro_plugin"
    macros = [
        random_number_macro,
    ]

The code above creates a macro that returns a random number between 0 and 1000. It can be referenced using Jinja templating in any templateable parameter of any operator. The code snippet below shows how the macro can be used within the bash_command parameter of the BashOperator to print out a random number.

use_plugin_macro = BashOperator(
    task_id="use_plugin_macro",
    bash_command="echo {{ macros.my_macro_plugin.random_number_macro() }}",
)

Airflow listeners​

Airflow listeners allow you to execute custom code when certain events occur anywhere in your Airflow instance, for example whenever any DAG run fails or an update to any dataset is detected.

Listeners execute based on the event they are waiting for and are not attached to a task or DAG. This is in contrast to Airflow callbacks which are attached to a specific DAG or (set of) task(s) or Airflow dataset consumer DAGs that only execute when a specific (set of) dataset(s) is updated. While the listener itself will execute any time its event occurs, you can use conditional logic to determine whether or not to execute the code within the listener. For example, you can use a listener to send a Slack notification when a DAG run fails, but only if the DAG run was not manually triggered.

You can create a listener using the @hookimpl decorator on functions defined with the same name and parameters as listed in the listeners spec source code.

For example, the @hookspec of the on_task_instance_failed function is:

@hookspec
def on_task_instance_failed(
    previous_state: TaskInstanceState | None, task_instance: TaskInstance, session: Session | None
):
    """Execute when task state changes to FAIL. previous_state can be None."""

In order to create a listener that executes whenever any task instance fails in your whole Airflow environment, you need to define a function called on_task_instance_failed that takes three parameters: previous_state, task_instance and session. Then, you decorate it with @hookimpl.

from airflow.listeners import hookimpl

@hookimpl
def on_task_instance_failed(
    previous_state: TaskInstanceState | None, task_instance: TaskInstance, session: Session | None
):
    # Your code here

The listener file can then be registered as a plugin by adding it to the listeners component of the plugin class.

from airflow.plugins_manager import AirflowPlugin
from plugins import listener_code


class MyListenerPlugin(AirflowPlugin):
    name = "my_listener_plugin"
    listeners = [listener_code]

To see a full example of how to create and register a listener, check out the Use a listener to send a Slack notification when a Dataset is updated tutorial.