 .. Licensed to the Apache Software Foundation (ASF) under one
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    to you under the Apache License, Version 2.0 (the
    "License"); you may not use this file except in compliance
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 ..   http://www.apache.org/licenses/LICENSE-2.0

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    software distributed under the License is distributed on an
    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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    under the License.

Installation from PyPI
----------------------

This page describes installations using the ``apache-airflow`` package `published in
PyPI <https://pypi.org/project/apache-airflow/>`__.

Installation tools
''''''''''''''''''

Only ``pip`` installation is currently officially supported.

While there are some successes with using other tools like `poetry <https://python-poetry.org/>`_ or
`pip-tools <https://pypi.org/project/pip-tools/>`_, they do not share the same workflow as
``pip`` - especially when it comes to constraint vs. requirements management.
Installing via ``Poetry`` or ``pip-tools`` is not currently supported. If you wish to install airflow
using those tools you should use the constraints and convert them to appropriate
format and workflow that your tool requires.

Typical command to install airflow from PyPI looks like below:

.. code-block::

    pip install "apache-airflow[celery]==|version|" --constraint "https://raw.githubusercontent.com/apache/airflow/constraints-|version|/constraints-3.6.txt"

This is an example, see further for more explanation.

.. _installation:constraints:

Constraints files
'''''''''''''''''

Airflow installation might be sometimes tricky because Airflow is a bit of both a library and application.
Libraries usually keep their dependencies open and applications usually pin them, but we should do neither
and both at the same time. We decided to keep our dependencies as open as possible
(in ``setup.cfg`` and ``setup.py``) so users can install different
version of libraries if needed. This means that from time to time plain ``pip install apache-airflow`` will
not work or will produce unusable Airflow installation.

In order to have repeatable installation, we also keep a set of "known-to-be-working" constraint files in the
``constraints-main``, ``constraints-2-0``, ``constraints-2-1`` etc. orphan branches and then we create tag
for each released version e.g. :subst-code:`constraints-|version|`. This way, when we keep a tested and working set of dependencies.

Those "known-to-be-working" constraints are per major/minor Python version. You can use them as constraint
files when installing Airflow from PyPI. Note that you have to specify correct Airflow version
and Python versions in the URL.

You can create the URL to the file substituting the variables in the template below.

.. code-block::

  https://raw.githubusercontent.com/apache/airflow/constraints-${AIRFLOW_VERSION}/constraints-${PYTHON_VERSION}.txt

where:

- ``AIRFLOW_VERSION`` - Airflow version (e.g. :subst-code:`|version|`) or ``main``, ``2-0``, for latest development version
- ``PYTHON_VERSION`` Python version e.g. ``3.8``, ``3.7``

There is also a no-providers constraint file, which contains just constraints required to install Airflow core. This allows
to install and upgrade airflow separately and independently from providers.

You can create the URL to the file substituting the variables in the template below.

.. code-block::

  https://raw.githubusercontent.com/apache/airflow/constraints-${AIRFLOW_VERSION}/constraints-no-providers-${PYTHON_VERSION}.txt

Installation and upgrade scenarios
''''''''''''''''''''''''''''''''''

In order to simplify the installation, we have prepared examples of how to upgrade Airflow and providers.

Installing Airflow with extras and providers
============================================

If you need to install extra dependencies of airflow, you can use the script below to make an installation
a one-liner (the example below installs postgres and google provider, as well as ``async`` extra.

.. code-block:: bash
    :substitutions:

    AIRFLOW_VERSION=|version|
    PYTHON_VERSION="$(python --version | cut -d " " -f 2 | cut -d "." -f 1-2)"
    CONSTRAINT_URL="https://raw.githubusercontent.com/apache/airflow/constraints-${AIRFLOW_VERSION}/constraints-${PYTHON_VERSION}.txt"
    pip install "apache-airflow[async,postgres,google]==${AIRFLOW_VERSION}" --constraint "${CONSTRAINT_URL}"

Note, that it will install the versions of providers that were available at the moment this version of Airflow
has been prepared. You need to follow next steps if you want to upgrade provider packages in case they were
released afterwards.


Upgrading Airflow with providers
================================

You can upgrade airflow together with extras (providers available at the time of the release of Airflow
being installed.


.. code-block:: bash
    :substitutions:

    AIRFLOW_VERSION=|version|
    PYTHON_VERSION="$(python --version | cut -d " " -f 2 | cut -d "." -f 1-2)"
    CONSTRAINT_URL="https://raw.githubusercontent.com/apache/airflow/constraints-${AIRFLOW_VERSION}/constraints-${PYTHON_VERSION}.txt"
    pip install --upgrade "apache-airflow[postgres,google]==${AIRFLOW_VERSION}" --constraint "${CONSTRAINT_URL}"

Installation and upgrading of Airflow providers separately
==========================================================

You can manually install all the providers you need. You can continue using the "providers" constraint files
but the 'versioned' airflow constraints installs only the versions of providers that were available in PyPI at
the time of preparing of the airflow version. However, usually you can use "main" version of the providers
to install latest version of providers. Usually the providers work with most versions of Airflow, if there
will be any incompatibilities, it will be captured as package dependencies.

.. code-block:: bash

    PYTHON_VERSION="$(python --version | cut -d " " -f 2 | cut -d "." -f 1-2)"
    # For example: 3.6
    CONSTRAINT_URL="https://raw.githubusercontent.com/apache/airflow/constraints-main/constraints-${PYTHON_VERSION}.txt"
    pip install "apache-airflow-providers-google" --constraint "${CONSTRAINT_URL}"

You can also upgrade the providers to latest versions (you need to use main version of constraints for that):

.. code-block:: bash

    PYTHON_VERSION="$(python --version | cut -d " " -f 2 | cut -d "." -f 1-2)"
    # For example: 3.6
    CONSTRAINT_URL="https://raw.githubusercontent.com/apache/airflow/constraints-main/constraints-${PYTHON_VERSION}.txt"
    pip install "apache-airflow-providers-google" --upgrade --constraint "${CONSTRAINT_URL}"


Installation and upgrade of Airflow core
========================================

If you don't want to install any extra providers, initially you can use the command set below.

.. code-block:: bash
    :substitutions:

    AIRFLOW_VERSION=|version|
    PYTHON_VERSION="$(python --version | cut -d " " -f 2 | cut -d "." -f 1-2)"
    # For example: 3.6
    CONSTRAINT_URL="https://raw.githubusercontent.com/apache/airflow/constraints-${AIRFLOW_VERSION}/constraints-no-providers-${PYTHON_VERSION}.txt"
    # For example: https://raw.githubusercontent.com/apache/airflow/constraints-|version|/constraints-no-providers-3.6.txt
    pip install "apache-airflow==${AIRFLOW_VERSION}" --constraint "${CONSTRAINT_URL}"


Troubleshooting
'''''''''''''''

This section describes how to troubleshoot installation issues with PyPI installation.

Airflow command is not recognized
=================================

If the ``airflow`` command is not getting recognized (can happen on Windows when using WSL), then
ensure that ``~/.local/bin`` is in your ``PATH`` environment variable, and add it in if necessary:

.. code-block:: bash

    PATH=$PATH:~/.local/bin

You can also start airflow with ``python -m airflow``

Symbol not found: ``_Py_GetArgcArgv``
=====================================

If you see ``Symbol not found: _Py_GetArgcArgv`` while starting or importing Airflow, this may mean that you are using an incompatible version of Python.
For a homebrew installed version of Python, this is generally caused by using Python in ``/usr/local/opt/bin`` rather than the Frameworks installation (e.g. for ``python 3.7``: ``/usr/local/opt/python@3.7/Frameworks/Python.framework/Versions/3.7``).

The crux of the issue is that a library Airflow depends on, ``setproctitle``, uses a non-public Python API
which is not available from the standard installation ``/usr/local/opt/`` (which symlinks to a path under ``/usr/local/Cellar``).

An easy fix is just to ensure you use a version of Python that has a dylib of the Python library available. For example:

.. code-block:: bash

  # Note: these instructions are for python3.7 but can be loosely modified for other versions
  brew install python@3.7
  virtualenv -p /usr/local/opt/python@3.7/Frameworks/Python.framework/Versions/3.7/bin/python3 .toy-venv
  source .toy-venv/bin/activate
  pip install apache-airflow
  python
  >>> import setproctitle
  # Success!

Alternatively, you can download and install Python directly from the `Python website <https://www.python.org/>`__.