Migration Patterns Reference

Migration Patterns Reference

Detailed code examples for Airflow 2 to 3 migration.

Table of Contents

• Removed Modules & Import Reorganizations
• Task SDK & Param Usage
• SubDAGs, SLAs, and Removed Features
• Scheduling & Context Changes
• XCom Pickling Removal
• Datasets to Assets
• DAG Bundles & File Paths

Removed Modules & Import Reorganizations

airflow.contrib.* removed

The entire airflow.contrib.* namespace is removed in Airflow 3.

Before (Airflow 2.x, removed in Airflow 3):

from airflow.contrib.operators.dummy_operator import DummyOperator

After (Airflow 3):

from airflow.providers.standard.operators.empty import EmptyOperator

Use EmptyOperator instead of the removed DummyOperator.

Core operators moved to provider packages

Many commonly used core operators moved to the standard provider.

Example for BashOperator and PythonOperator:

# Airflow 2 legacy imports (removed in Airflow 3, AIR30/AIR301)
from airflow.operators.bash_operator import BashOperator
from airflow.operators.python_operator import PythonOperator

# Airflow 2/3 deprecated imports (still work but deprecated, AIR31/AIR311)
from airflow.operators.bash import BashOperator
from airflow.operators.python import PythonOperator

# Recommended in Airflow 3: Standard provider
from airflow.providers.standard.operators.bash import BashOperator
from airflow.providers.standard.operators.python import PythonOperator

Operators moved to the apache-airflow-providers-standard package include (non-exhaustive):

• BashOperator
• BranchDateTimeOperator
• BranchDayOfWeekOperator
• LatestOnlyOperator
• PythonOperator
• PythonVirtualenvOperator
• ExternalPythonOperator
• BranchPythonOperator
• BranchPythonVirtualenvOperator
• BranchExternalPythonOperator
• ShortCircuitOperator
• TriggerDagRunOperator

This provider is installed on Astro Runtime by default.

Hook and sensor imports moved to providers

Most hooks and sensors live in provider packages in Airflow 3. Look for very old imports:

from airflow.hooks.http_hook import HttpHook
from airflow.hooks.base_hook import BaseHook

Replace with provider imports:

from airflow.providers.http.hooks.http import HttpHook
from airflow.sdk import BaseHook  # base hook from task SDK where appropriate

EmailOperator moved to SMTP provider

In Airflow 3, EmailOperator is provided by the SMTP provider, not the standard provider.

from airflow.providers.smtp.operators.smtp import EmailOperator

EmailOperator(
    task_id="send_email",
    conn_id="smtp_default",
    to="receiver@example.com",
    subject="Test Email",
    html_content="This is a test email",
)

Ensure apache-airflow-providers-smtp is added to any project that uses email features or notifications so that email-related code is compatible with Airflow 3.2 and later.

Replacing legacy email notifications: Move towards SMTP-provider based callbacks (and eventually SmtpNotifier) instead of relying on legacy task-level email behavior:

from airflow.providers.smtp.notifications.smtp import send_smtp_notification

BashOperator(
    task_id="my_task",
    bash_command="exit 1",
   
        send_smtp_notification(
            from_email="airflow@my_domain.com",
            to="my_name@my_domain.ch",
            subject="[Error] The Task {{ ti.task_id }} failed",
            html_content="debug logs",
        )
    ],
)

Astro users: Consider Astro Alerts for critical notifications (works independently of Airflow components).

Task SDK & Param Usage

In Airflow 3, most classes and decorators used by DAG authors are available via the Task SDK (airflow.sdk). Using these imports makes it easier to evolve your code with future Airflow versions.

Key Task SDK imports

Prefer these imports in new code:

from airflow.sdk import (
    dag,
    task,
    setup,
    teardown,
    DAG,
    TaskGroup,
    BaseOperator,
    BaseSensorOperator,
    Param,
    ParamsDict,
    Variable,
    Connection,
    Context,
    Asset,
    AssetAlias,
    AssetAll,
    AssetAny,
    DagRunState,
    TaskInstanceState,
    TriggerRule,
    WeightRule,
    BaseHook,
    BaseNotifier,
    XComArg,
    chain,
    chain_linear,
    cross_downstream,
    get_current_context,
)

Import mappings from legacy to Task SDK

SubDAGs, SLAs, and Removed Features

SubDAGs removed

Search for:

• SubDagOperator(
• from airflow.operators.subdag_operator import SubDagOperator
• from airflow.operators.subdag import SubDagOperator

Migration guidance:

• Use TaskGroup or @task_group for logical grouping within a single DAG.
• For workflows that were previously split via SubDAGs, consider:
  • Refactoring into smaller DAGs.
  • Using Assets (formerly Datasets) for cross-DAG dependencies.

SLAs removed

Search for:

• sla=
• sla_miss_callback
• SLAMiss

Code changes:

• Remove SLA-related parameters from tasks and DAGs.
• Remove SLA-based callbacks from DAG definitions.
• On Astro, use Astro Alerts for DAG/task-level SLAs.

Other removed or renamed code features

• DagParam removed - use Param from airflow.sdk.
• SimpleHttpOperator removed - use HttpOperator from the HTTP provider.
• Trigger rules:
  • dummy - use TriggerRule.ALWAYS.
  • none_failed_or_skipped - use TriggerRule.NONE_FAILED_MIN_ONE_SUCCESS.
• .xcom_pull behavior:
  • In Airflow 3, calling xcom_pull(key="...") without task_ids always returns None; always specify task_ids explicitly.
• fail_stop DAG parameter renamed to fail_fast.
• max_active_tasks now limits active task instances per DAG run instead of across all DAG runs.
• on_success_callback no longer runs on skip; use on_skipped_callback if needed.
• @teardown with TriggerRule.ALWAYS not allowed; teardowns now execute even if DAG run terminated early.
• templates_dict removed - use params via context["params"].
• expanded_ti_count removed - use REST API "Get Mapped Task Instances" endpoint.
• dag_run.external_trigger removed - infer from dag_run.run_type.
• test_mode removed; avoid relying on this flag.
• Cannot trigger a DAG with a logical_date in the future; use logical_date=None and rely on run_id instead.

Scheduling & Context Changes

Default scheduling behavior

Airflow 3 changes default DAG scheduling:

• schedule=None instead of timedelta(days=1).
• catchup=False instead of True.

Code impact:

• If a DAG relied on implicit daily scheduling, explicitly set schedule.
• If a DAG relied on catchup by default, explicitly set catchup=True.

Removed context keys and replacements

Note: These replacements are not always drop-in; logic changes may be required.

Asset-triggered runs: logical_date may be None. Use defensive access: context["dag_run"].logical_date or context["run_id"].

days_ago removed

The helper days_ago from airflow.utils.dates was removed. Replace with explicit datetimes:

# WRONG - Removed in Airflow 3
from airflow.utils.dates import days_ago
start_date=days_ago(2)

# CORRECT - Use pendulum
import pendulum
start_date=pendulum.today("UTC").add(days=-2)

XCom Pickling Removal

In Airflow 3:

• AIRFLOW__CORE__ENABLE_XCOM_PICKLING is removed.
• The default XCom backend requires values to be serializable (for most users this means JSON-serializable values).

If tasks need to pass complex objects (e.g. NumPy arrays), you must use a custom XCom backend.

Example custom backend for NumPy arrays:

from airflow.sdk.bases.xcom import BaseXCom
import json
import numpy as np

class NumpyXComBackend(BaseXCom):
    @staticmethod
    def serialize_value(value, **kwargs):
        if isinstance(value, np.ndarray):
            return json.dumps({"type": "ndarray", "data": value.tolist(), "dtype": str(value.dtype)}).encode()
        return BaseXCom.serialize_value(value)

    @staticmethod
    def deserialize_value(result):
        if isinstance(result.value, bytes):
            d = json.loads(result.value.decode("utf-8"))
            if d.get("type") == "ndarray":
                return np.array(d["data"], dtype=d["dtype"])
        return BaseXCom.deserialize_value(result)

Reference: https://www.astronomer.io/docs/learn/custom-xcom-backend-strategies

Datasets to Assets

Datasets were renamed to Assets in Airflow 3; the old APIs are deprecated.

Mappings:

When working with asset events in the task context, do not use plain strings as keys in outlet_events or inlet_events:

# WRONG
outlet_events["myasset"]

# CORRECT
from airflow.sdk import Asset
outlet_events[Asset(name="myasset")]

Reading asset event data:

from airflow.sdk import task

@task
def read_triggering_assets(**context):
    events = context.get("triggering_asset_events") or {}
    for asset, asset_events in events.items():
        first_event = asset_events[0]
        print(asset, first_event.source_run_id)

Cosmos/dbt note: Asset URIs changed from dots to slashes (schema.table → schema/table). Upgrade astronomer-cosmos to >= 1.10.0 for Airflow 3 compatibility (and >= 1.11.0 if you need dbt Docs hosting in the Airflow UI).

DAG Bundles & File Paths

On Astro Runtime, Airflow 3 uses a versioned DAG bundle, so file paths behave differently:

For files inside dags/ folder:

import os
dag_dir = os.path.dirname(__file__)
with open(os.path.join(dag_dir, "my_file.txt"), "r") as f:
    contents = f.read()

For files in include/ or other mounted folders:

import os
with open(f"{os.getenv('AIRFLOW_HOME')}/include/my_file.txt", 'r') as f:
    contents = f.read()

For template_searchpath:

import os
from airflow.sdk import dag

@dag(template_searchpath=[f"{os.getenv('AIRFLOW_HOME')}/include/sql"])
def my_dag():
    ...

Note: Triggers cannot be in the DAG bundle; they must be elsewhere on sys.path.