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https://github.com/fridex/s2i-example-micropipenv

An example of micropipenv as part of OpenShift's Python s2i (source-to-image) container image build process
https://github.com/fridex/s2i-example-micropipenv

dependency-management micropipenv pip pip3 pipenv poetry

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An example of micropipenv as part of OpenShift's Python s2i (source-to-image) container image build process

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README 

        
micropipenv example for OpenShift's Python s2i

----------------------------------------------



This repository contains all the materials needed to test and demo `micropipenv

`_ in OpenShift's s2i container

image build process.



The application consists of a simple Flask server that is built and deployed

into OpenShift.



Installation instructions

=========================



To install this application into your OpenShift namespace, run the following

command:



.. code-block:: console



   oc project 

   oc process -f https://raw.githubusercontent.com/fridex/s2i-example-micropipenv/master/openshift.yaml | oc apply -f -



After triggering the given command the application named

"s2i-example-micropipenv" should be built in your namespace.



micropipenv lock file discovery

===============================



Check `micropipenv documentation

`_ for the automatic lock file

discovery.  micropipenv looks for files describing dependencies in the

following order:



1. Pipenv files - ``Pipfile.lock`` and ``Pipfile``

2. Poetry files - ``poetry.lock`` and ``pyproject.toml``

3. requirements.txt files for ``pip-tools`` style requirements or raw requirements.txt



As micropipenv unifies build log output across all the dependency managers, it

might be not directly visible what file is used (DEBUG mode can be helpful for

this case). To distinguish which file was used as a source for requirements,

this demo pins different versions of Flask for different cases.



Demo Pipenv support

===================



To test Python s2i with Pipenv functionality, run application without any

changes (Pipenv has the highest priority). Based on the lock file, you should

be able to see Flask in version 1.0.1 installed and the application should be

running.



.. figure:: https://raw.githubusercontent.com/fridex/s2i-example-micropipenv/master/fig/pipfile_lock.png

   :alt: Build log screen shot (part of it).

   :align: center



Demo Poetry support

===================



Now, let's rename our ``Pipfile.lock`` so micropipenv does not find it and

fallbacks to Poetry style requirements:



.. code-block:: console



  mv Pipfile.lock Pipfile.lock_bac



Let's start the build and use the content of the local directory as a package

source (to avoid committing to Git):



.. code-block:: console



  oc start-build --from-dir=. s2i-example-micropipenv



As Poetry style requirements are used, you should be able to see Flask in

version 1.0.3 being installad. The Python s2i build process prints the

installed stack onto standard error output (to unify logs, ``Pipfile.lock``

format is used). Mind the logs are identical with the scenario before where we

used Pipenv (the difference is in Flask version).



Demo pip-tools support

======================



Let's perform similar operation as before to let micropipenv install

dependencies from ``requirements.txt`` that have lowest priority:



.. code-block:: console



  mv poetry.lock poetry.lock_bac



And start the build process once again:



.. code-block:: console



  oc start-build --from-dir=. s2i-example-micropipenv



The ``requirements.txt`` file pins down Flask to version 1.1.1. You should see

this version of Flask being installed in the OpenShift's build logs.



Note the ``requirements.txt`` file was produced using ``pip-tools`` with

``--require-hashes`` being set. Note the build log has identical structure as

in the previous Pipenv and Poetry scenarios (the difference is in Flask version).



Demo pip support

================



Now, let's demo the last use case - ``requirements.txt`` does not state full

stack of Python libraries that should be installed. This is a bad practice as

the application deployed hasn't all stated dependencies. The packages

installed can be different if you trigger the build tomorrow or one year later.

It's also harder for maintainers (assuming source code only access) to track

down what packages the developer used to run the application.



.. code-block:: console



  mv requirements.txt requirements.txt{,_bac}

  mv requirements_unpinned.txt requirements.txt



After triggering the build, you should see a big warning about unpinned Python

application stack produced:



.. code-block:: console



  oc start-build --from-dir=. s2i-example-micropipenv



To notify Python s2i user what packages are installed, micropipenv populates

``pip freeze`` output to Python s2i build logs.



.. figure:: https://raw.githubusercontent.com/fridex/s2i-example-micropipenv/master/fig/requirements_unpinned.png

   :alt: Warning produced when Python requirements are not pinned down.

   :align: center



Explictly specifying requirements file

======================================



You can also provide ``MICROPIPENV_METHOD`` environment variable to the

OpenShift build process to make sure your desired installation method is used.

Refer to micropipenv docs for more info. See also ``openshift.yaml`` and

comments in the build configuration.



micropipenv vs Pipenv size

==========================



Let's compare size needed for installing Pipenv and micropipenv (size and

software shipped to prod matters) - the test was done on Fedora 31 with Python

3.7:



.. code-block:: console



  $ python3 -m venv venv_pipenv

  $ . venv_pipenv/bin/activate

  $ du -s -B1 venv_pipenv

  11210752	venv_pipenv

  $ pip3 install pipenv

  $ du -s -B1 venv_pipenv

  42049536	venv_pipenv

  $ deactivate



And now with micropipenv:



.. code-block:: console



  $ python3 -m venv venv_micropipenv

  $ . venv_micropipenv/bin/activate

  $ du -s -B1 venv_micropipenv

  11210752      venv_micropipenv

  $ pip3 install 'micropipenv[toml]'

  $ du -s -B1 venv_micropipenv

  11595776      venv_micropipenv

  $ deactivate



That's 30453760 bytes (30.4 Megabyte) difference!



Clean up

========



To clean up your name space after the demo, you can run the following command:



.. code-block:: console



  $ oc delete -l app=s2i-example-micropipenv bc,is,dc,route,svc